Merge pull request #262 from whitevegagabriel/l2cap

Port l2cap_bridge sample to Rust

.github/workflows/python-build-test.yml

@@ -45,7 +45,8 @@ jobs:
     runs-on: ubuntu-latest
     strategy:
       matrix:
-        python-version: [ "3.8", "3.9", "3.10" ]
+        python-version: [ "3.8", "3.9", "3.10", "3.11" ]
+        rust-version: [ "1.70.0", "stable" ]
       fail-fast: false
     steps:
       - name: Check out from Git
@@ -62,9 +63,15 @@ jobs:
         uses: actions-rust-lang/setup-rust-toolchain@v1
         with:
           components: clippy,rustfmt
-      - name: Rust Lints
-        run: cd rust && cargo fmt --check && cargo clippy --all-targets -- --deny warnings
+          toolchain: ${{ matrix.rust-version }}
       - name: Rust Build
-        run: cd rust && cargo build --all-targets
+        run: cd rust && cargo build --all-targets && cargo build --all-features --all-targets
+      # Lints after build so what clippy needs is already built
+      - name: Rust Lints
+        run: cd rust && cargo fmt --check && cargo clippy --all-targets -- --deny warnings && cargo clippy --all-features --all-targets -- --deny warnings
       - name: Rust Tests
-        run: cd rust && cargo test
+        run: cd rust && cargo test
+      # At some point, hook up publishing the binary. For now, just make sure it builds.
+      # Once we're ready to publish binaries, this should be built with `--release`.
+      - name: Build Bumble CLI
+        run: cd rust && cargo build --features bumble-tools --bin bumble

apps/l2cap_bridge.py

@@ -105,7 +105,7 @@ class ServerBridge:
                             asyncio.create_task(self.pipe.l2cap_channel.disconnect())
 
                     def data_received(self, data):
-                        print(f'<<< Received on TCP: {len(data)}')
+                        print(color(f'<<< [TCP DATA]: {len(data)} bytes', 'blue'))
                         self.pipe.l2cap_channel.write(data)
 
                 try:
@@ -123,6 +123,7 @@ class ServerBridge:
                     await self.l2cap_channel.disconnect()
 
             def on_l2cap_close(self):
+                print(color('*** L2CAP channel closed', 'red'))
                 self.l2cap_channel = None
                 if self.tcp_transport is not None:
                     self.tcp_transport.close()

bumble/drivers/__init__.py

@@ -21,6 +21,9 @@ like loading firmware after a cold start.
 # -----------------------------------------------------------------------------
 import abc
 import logging
+import pathlib
+import platform
+import platformdirs
 from . import rtk
 
 
@@ -66,3 +69,22 @@ async def get_driver_for_host(host):
         return driver
 
     return None
+
+
+def project_data_dir() -> pathlib.Path:
+    """
+    Returns:
+        A path to an OS-specific directory for bumble data. The directory is created if
+         it doesn't exist.
+    """
+    if platform.system() == 'Darwin':
+        # platformdirs doesn't handle macOS right: it doesn't assemble a bundle id
+        # out of author & project
+        return platformdirs.user_data_path(
+            appname='com.google.bumble', ensure_exists=True
+        )
+    else:
+        # windows and linux don't use the com qualifier
+        return platformdirs.user_data_path(
+            appname='bumble', appauthor='google', ensure_exists=True
+        )

bumble/drivers/rtk.py

@@ -446,6 +446,11 @@ class Driver:
             # When the environment variable is set, don't look elsewhere
             return None
 
+        # Then, look where the firmware download tool writes by default
+        if (path := rtk_firmware_dir() / file_name).is_file():
+            logger.debug(f"{file_name} found in project data dir")
+            return path
+
         # Then, look in the package's driver directory
         if (path := pathlib.Path(__file__).parent / "rtk_fw" / file_name).is_file():
             logger.debug(f"{file_name} found in package dir")
@@ -646,3 +651,16 @@ class Driver:
         await self.download_firmware()
         await self.host.send_command(HCI_Reset_Command(), check_result=True)
         logger.info(f"loaded FW image {self.driver_info.fw_name}")
+
+
+def rtk_firmware_dir() -> pathlib.Path:
+    """
+    Returns:
+        A path to a subdir of the project data dir for Realtek firmware.
+         The directory is created if it doesn't exist.
+    """
+    from bumble.drivers import project_data_dir
+
+    p = project_data_dir() / "firmware" / "realtek"
+    p.mkdir(parents=True, exist_ok=True)
+    return p

rust/Cargo.toml

@@ -10,12 +10,12 @@ documentation = "https://docs.rs/crate/bumble"
 authors = ["Marshall Pierce <marshallpierce@google.com>"]
 keywords = ["bluetooth", "ble"]
 categories = ["api-bindings", "network-programming"]
-rust-version = "1.69.0"
+rust-version = "1.70.0"
 
 [dependencies]
 pyo3 = { version = "0.18.3", features = ["macros"] }
 pyo3-asyncio = { version = "0.18.0", features = ["tokio-runtime"] }
-tokio = { version = "1.28.2" }
+tokio = { version = "1.28.2", features = ["macros", "signal"] }
 nom = "7.1.3"
 strum = "0.25.0"
 strum_macros = "0.25.0"
@@ -23,7 +23,17 @@ hex = "0.4.3"
 itertools = "0.11.0"
 lazy_static = "1.4.0"
 thiserror = "1.0.41"
+
+# CLI
 anyhow = { version = "1.0.71", optional = true }
+clap = { version = "4.3.3", features = ["derive"], optional = true }
+directories = { version = "5.0.1", optional = true }
+env_logger = { version = "0.10.0", optional = true }
+futures = { version = "0.3.28", optional = true }
+log = { version = "0.4.19", optional = true }
+owo-colors = { version = "3.5.0", optional = true }
+reqwest = { version = "0.11.20", features = ["blocking"], optional = true }
+rusb = { version = "0.9.2", optional = true }
 
 [dev-dependencies]
 tokio = { version = "1.28.2", features = ["full"] }
@@ -32,17 +42,25 @@ nix = "0.26.2"
 anyhow = "1.0.71"
 pyo3 = { version = "0.18.3", features = ["macros", "anyhow"] }
 pyo3-asyncio = { version = "0.18.0", features = ["tokio-runtime", "attributes", "testing"] }
+rusb = "0.9.2"
+rand = "0.8.5"
 clap = { version = "4.3.3", features = ["derive"] }
 owo-colors = "3.5.0"
 log = "0.4.19"
 env_logger = "0.10.0"
-rusb = "0.9.2"
-rand = "0.8.5"
+
+[package.metadata.docs.rs]
+rustdoc-args = ["--generate-link-to-definition"]
 
 [[bin]]
 name = "gen-assigned-numbers"
 path = "tools/gen_assigned_numbers.rs"
-required-features = ["bumble-dev-tools"]
+required-features = ["bumble-codegen"]
+
+[[bin]]
+name = "bumble"
+path = "src/main.rs"
+required-features = ["bumble-tools"]
 
 # test entry point that uses pyo3_asyncio's test harness
 [[test]]
@@ -53,4 +71,7 @@ harness = false
 [features]
 anyhow = ["pyo3/anyhow"]
 pyo3-asyncio-attributes = ["pyo3-asyncio/attributes"]
-bumble-dev-tools = ["dep:anyhow"]
+bumble-codegen = ["dep:anyhow"]
+# separate feature for CLI so that dependencies don't spend time building these
+bumble-tools = ["dep:clap", "anyhow", "dep:anyhow", "dep:directories", "pyo3-asyncio-attributes", "dep:owo-colors", "dep:reqwest", "dep:rusb", "dep:log", "dep:env_logger", "dep:futures"]
+default = []

rust/README.md

@@ -5,7 +5,8 @@ Rust wrappers around the [Bumble](https://github.com/google/bumble) Python API.
 Method calls are mapped to the equivalent Python, and return types adapted where
 relevant.
 
-See the `examples` directory for usage.
+See the CLI in `src/main.rs` or the `examples` directory for how to use the
+Bumble API.
 
 # Usage
 
@@ -27,6 +28,15 @@ PYTHONPATH=..:~/.virtualenvs/bumble/lib/python3.10/site-packages/ \
 Run the corresponding `battery_server` Python example, and launch an emulator in
 Android Studio (currently, Canary is required) to run netsim.
 
+# CLI
+
+Explore the available subcommands:
+
+```
+PYTHONPATH=..:[virtualenv site-packages] \
+    cargo run --features bumble-tools --bin bumble -- --help
+```
+
 # Development
 
 Run the tests:
@@ -43,7 +53,7 @@ cargo clippy --all-targets
 
 ## Code gen
 
-To have the fastest startup while keeping the build simple, code gen for 
+To have the fastest startup while keeping the build simple, code gen for
 assigned numbers is done with the `gen_assigned_numbers` tool. It should
 be re-run whenever the Python assigned numbers are changed. To ensure that the
 generated code is kept up to date, the Rust data is compared to the Python
@@ -52,5 +62,5 @@ in tests at `pytests/assigned_numbers.rs`.
 To regenerate the assigned number tables based on the Python codebase:
 
 ```
-PYTHONPATH=.. cargo run --bin gen-assigned-numbers --features bumble-dev-tools
+PYTHONPATH=.. cargo run --bin gen-assigned-numbers --features bumble-codegen
 ```

rust/pytests/wrapper.rs

@@ -12,7 +12,7 @@
 // See the License for the specific language governing permissions and
 // limitations under the License.
 
-use bumble::wrapper::transport::Transport;
+use bumble::wrapper::{drivers::rtk::DriverInfo, transport::Transport};
 use nix::sys::stat::Mode;
 use pyo3::PyResult;
 
@@ -29,3 +29,9 @@ async fn fifo_transport_can_open() -> PyResult<()> {
 
     Ok(())
 }
+
+#[pyo3_asyncio::tokio::test]
+async fn realtek_driver_info_all_drivers() -> PyResult<()> {
+    assert_eq!(12, DriverInfo::all_drivers()?.len());
+    Ok(())
+}

rust/resources/test/firmware/realtek/README.md

@@ -0,0 +1,4 @@
+This dir contains samples firmware images in the format used for Realtek chips,
+but with repetitions of the length of the section as a little-endian 32-bit int
+for the patch data instead of actual firmware, since we only need the structure
+to test parsing.

rust/src/cli/firmware/mod.rs

@@ -0,0 +1,15 @@
+// Copyright 2023 Google LLC
+//
+// Licensed under the Apache License, Version 2.0 (the "License");
+// you may not use this file except in compliance with the License.
+// You may obtain a copy of the License at
+//
+//     http://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS,
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// See the License for the specific language governing permissions and
+// limitations under the License.
+
+pub(crate) mod rtk;

rust/src/cli/firmware/rtk.rs

@@ -0,0 +1,265 @@
+// Copyright 2023 Google LLC
+//
+// Licensed under the Apache License, Version 2.0 (the "License");
+// you may not use this file except in compliance with the License.
+// You may obtain a copy of the License at
+//
+//     http://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS,
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// See the License for the specific language governing permissions and
+// limitations under the License.
+
+//! Realtek firmware tools
+
+use crate::{Download, Source};
+use anyhow::anyhow;
+use bumble::wrapper::{
+    drivers::rtk::{Driver, DriverInfo, Firmware},
+    host::{DriverFactory, Host},
+    transport::Transport,
+};
+use owo_colors::{colors::css, OwoColorize};
+use pyo3::PyResult;
+use std::{fs, path};
+
+pub(crate) async fn download(dl: Download) -> PyResult<()> {
+    let data_dir = dl
+        .output_dir
+        .or_else(|| {
+            directories::ProjectDirs::from("com", "google", "bumble")
+                .map(|pd| pd.data_local_dir().join("firmware").join("realtek"))
+        })
+        .unwrap_or_else(|| {
+            eprintln!("Could not determine standard data directory");
+            path::PathBuf::from(".")
+        });
+    fs::create_dir_all(&data_dir)?;
+
+    let (base_url, uses_bin_suffix) = match dl.source {
+        Source::LinuxKernel => ("https://git.kernel.org/pub/scm/linux/kernel/git/firmware/linux-firmware.git/plain/rtl_bt", true),
+        Source::RealtekOpensource => ("https://github.com/Realtek-OpenSource/android_hardware_realtek/raw/rtk1395/bt/rtkbt/Firmware/BT", false),
+        Source::LinuxFromScratch => ("https://anduin.linuxfromscratch.org/sources/linux-firmware/rtl_bt", true),
+    };
+
+    println!("Downloading");
+    println!("{} {}", "FROM:".green(), base_url);
+    println!("{} {}", "TO:".green(), data_dir.to_string_lossy());
+
+    let url_for_file = |file_name: &str| {
+        let url_suffix = if uses_bin_suffix {
+            file_name
+        } else {
+            file_name.trim_end_matches(".bin")
+        };
+
+        let mut url = base_url.to_string();
+        url.push('/');
+        url.push_str(url_suffix);
+        url
+    };
+
+    let to_download = if let Some(single) = dl.single {
+        vec![(
+            format!("{single}_fw.bin"),
+            Some(format!("{single}_config.bin")),
+            false,
+        )]
+    } else {
+        DriverInfo::all_drivers()?
+            .iter()
+            .map(|di| Ok((di.firmware_name()?, di.config_name()?, di.config_needed()?)))
+            .collect::<PyResult<Vec<_>>>()?
+    };
+
+    let client = SimpleClient::new();
+
+    for (fw_filename, config_filename, config_needed) in to_download {
+        println!("{}", "---".yellow());
+        let fw_path = data_dir.join(&fw_filename);
+        let config_path = config_filename.as_ref().map(|f| data_dir.join(f));
+
+        if fw_path.exists() && !dl.overwrite {
+            println!(
+                "{}",
+                format!("{} already exists, skipping", fw_path.to_string_lossy())
+                    .fg::<css::Orange>()
+            );
+            continue;
+        }
+        if let Some(cp) = config_path.as_ref() {
+            if cp.exists() && !dl.overwrite {
+                println!(
+                    "{}",
+                    format!("{} already exists, skipping", cp.to_string_lossy())
+                        .fg::<css::Orange>()
+                );
+                continue;
+            }
+        }
+
+        let fw_contents = match client.get(&url_for_file(&fw_filename)).await {
+            Ok(data) => {
+                println!("Downloaded {}: {} bytes", fw_filename, data.len());
+                data
+            }
+            Err(e) => {
+                eprintln!(
+                    "{} {} {:?}",
+                    "Failed to download".red(),
+                    fw_filename.red(),
+                    e
+                );
+                continue;
+            }
+        };
+
+        let config_contents = if let Some(cn) = &config_filename {
+            match client.get(&url_for_file(cn)).await {
+                Ok(data) => {
+                    println!("Downloaded {}: {} bytes", cn, data.len());
+                    Some(data)
+                }
+                Err(e) => {
+                    if config_needed {
+                        eprintln!("{} {} {:?}", "Failed to download".red(), cn.red(), e);
+                        continue;
+                    } else {
+                        eprintln!(
+                            "{}",
+                            format!("No config available as {cn}").fg::<css::Orange>()
+                        );
+                        None
+                    }
+                }
+            }
+        } else {
+            None
+        };
+
+        fs::write(&fw_path, &fw_contents)?;
+        if !dl.no_parse && config_filename.is_some() {
+            println!("{} {}", "Parsing:".cyan(), &fw_filename);
+            match Firmware::parse(&fw_contents).map_err(|e| anyhow!("Parse error: {:?}", e)) {
+                Ok(fw) => dump_firmware_desc(&fw),
+                Err(e) => {
+                    eprintln!(
+                        "{} {:?}",
+                        "Could not parse firmware:".fg::<css::Orange>(),
+                        e
+                    );
+                }
+            }
+        }
+        if let Some((cp, cd)) = config_path
+            .as_ref()
+            .and_then(|p| config_contents.map(|c| (p, c)))
+        {
+            fs::write(cp, &cd)?;
+        }
+    }
+
+    Ok(())
+}
+
+pub(crate) fn parse(firmware_path: &path::Path) -> PyResult<()> {
+    let contents = fs::read(firmware_path)?;
+    let fw = Firmware::parse(&contents)
+        // squish the error into a string to avoid the error type requiring that the input be
+        // 'static
+        .map_err(|e| anyhow!("Parse error: {:?}", e))?;
+
+    dump_firmware_desc(&fw);
+
+    Ok(())
+}
+
+pub(crate) async fn info(transport: &str, force: bool) -> PyResult<()> {
+    let transport = Transport::open(transport).await?;
+
+    let mut host = Host::new(transport.source()?, transport.sink()?)?;
+    host.reset(DriverFactory::None).await?;
+
+    if !force && !Driver::check(&host).await? {
+        println!("USB device not supported by this RTK driver");
+    } else if let Some(driver_info) = Driver::driver_info_for_host(&host).await? {
+        println!("Driver:");
+        println!("  {:10} {:04X}", "ROM:", driver_info.rom()?);
+        println!("  {:10} {}", "Firmware:", driver_info.firmware_name()?);
+        println!(
+            "  {:10} {}",
+            "Config:",
+            driver_info.config_name()?.unwrap_or_default()
+        );
+    } else {
+        println!("Firmware already loaded or no supported driver for this device.")
+    }
+
+    Ok(())
+}
+
+pub(crate) async fn load(transport: &str, force: bool) -> PyResult<()> {
+    let transport = Transport::open(transport).await?;
+
+    let mut host = Host::new(transport.source()?, transport.sink()?)?;
+    host.reset(DriverFactory::None).await?;
+
+    match Driver::for_host(&host, force).await? {
+        None => {
+            eprintln!("Firmware already loaded or no supported driver for this device.");
+        }
+        Some(mut d) => d.download_firmware().await?,
+    };
+
+    Ok(())
+}
+
+pub(crate) async fn drop(transport: &str) -> PyResult<()> {
+    let transport = Transport::open(transport).await?;
+
+    let mut host = Host::new(transport.source()?, transport.sink()?)?;
+    host.reset(DriverFactory::None).await?;
+
+    Driver::drop_firmware(&mut host).await?;
+
+    Ok(())
+}
+
+fn dump_firmware_desc(fw: &Firmware) {
+    println!(
+        "Firmware: version=0x{:08X} project_id=0x{:04X}",
+        fw.version(),
+        fw.project_id()
+    );
+    for p in fw.patches() {
+        println!(
+            "  Patch: chip_id=0x{:04X}, {} bytes, SVN Version={:08X}",
+            p.chip_id(),
+            p.contents().len(),
+            p.svn_version()
+        )
+    }
+}
+
+struct SimpleClient {
+    client: reqwest::Client,
+}
+
+impl SimpleClient {
+    fn new() -> Self {
+        Self {
+            client: reqwest::Client::new(),
+        }
+    }
+
+    async fn get(&self, url: &str) -> anyhow::Result<Vec<u8>> {
+        let resp = self.client.get(url).send().await?;
+        if !resp.status().is_success() {
+            return Err(anyhow!("Bad status: {}", resp.status()));
+        }
+        let bytes = resp.bytes().await?;
+        Ok(bytes.as_ref().to_vec())
+    }
+}

rust/src/cli/l2cap/client_bridge.rs

@@ -0,0 +1,191 @@
+// Copyright 2023 Google LLC
+//
+// Licensed under the Apache License, Version 2.0 (the "License");
+// you may not use this file except in compliance with the License.
+// You may obtain a copy of the License at
+//
+//     http://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS,
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// See the License for the specific language governing permissions and
+// limitations under the License.
+
+/// L2CAP CoC client bridge: connects to a BLE device, then waits for an inbound
+/// TCP connection on a specified port number. When a TCP client connects, an
+/// L2CAP CoC channel connection to the BLE device is established, and the data
+/// is bridged in both directions, with flow control.
+/// When the TCP connection is closed by the client, the L2CAP CoC channel is
+/// disconnected, but the connection to the BLE device remains, ready for a new
+/// TCP client to connect.
+/// When the L2CAP CoC channel is closed, the TCP connection is closed as well.
+use crate::cli::l2cap::{
+    proxy_l2cap_rx_to_tcp_tx, proxy_tcp_rx_to_l2cap_tx, run_future_with_current_task_locals,
+    BridgeData,
+};
+use bumble::wrapper::{
+    device::{Connection, Device},
+    hci::HciConstant,
+};
+use futures::executor::block_on;
+use owo_colors::OwoColorize;
+use pyo3::{PyResult, Python};
+use std::{net::SocketAddr, sync::Arc};
+use tokio::{
+    join,
+    net::{TcpListener, TcpStream},
+    sync::{mpsc, Mutex},
+};
+
+pub struct Args {
+    pub psm: u16,
+    pub max_credits: Option<u16>,
+    pub mtu: Option<u16>,
+    pub mps: Option<u16>,
+    pub bluetooth_address: String,
+    pub tcp_host: String,
+    pub tcp_port: u16,
+}
+
+pub async fn start(args: &Args, device: &mut Device) -> PyResult<()> {
+    println!(
+        "{}",
+        format!("### Connecting to {}...", args.bluetooth_address).yellow()
+    );
+    let mut ble_connection = device.connect(&args.bluetooth_address).await?;
+    ble_connection.on_disconnection(|_py, reason| {
+        let disconnection_info = match HciConstant::error_name(reason) {
+            Ok(info_string) => info_string,
+            Err(py_err) => format!("failed to get disconnection error name ({})", py_err),
+        };
+        println!(
+            "{} {}",
+            "@@@ Bluetooth disconnection: ".red(),
+            disconnection_info,
+        );
+        Ok(())
+    })?;
+
+    // Start the TCP server.
+    let listener = TcpListener::bind(format!("{}:{}", args.tcp_host, args.tcp_port))
+        .await
+        .expect("failed to bind tcp to address");
+    println!(
+        "{}",
+        format!(
+            "### Listening for TCP connections on port {}",
+            args.tcp_port
+        )
+        .magenta()
+    );
+
+    let psm = args.psm;
+    let max_credits = args.max_credits;
+    let mtu = args.mtu;
+    let mps = args.mps;
+    let ble_connection = Arc::new(Mutex::new(ble_connection));
+    // Ensure Python event loop is available to l2cap `disconnect`
+    let _ = run_future_with_current_task_locals(async move {
+        while let Ok((tcp_stream, addr)) = listener.accept().await {
+            let ble_connection = ble_connection.clone();
+            let _ = run_future_with_current_task_locals(proxy_data_between_tcp_and_l2cap(
+                ble_connection,
+                tcp_stream,
+                addr,
+                psm,
+                max_credits,
+                mtu,
+                mps,
+            ));
+        }
+        Ok(())
+    });
+    Ok(())
+}
+
+async fn proxy_data_between_tcp_and_l2cap(
+    ble_connection: Arc<Mutex<Connection>>,
+    tcp_stream: TcpStream,
+    addr: SocketAddr,
+    psm: u16,
+    max_credits: Option<u16>,
+    mtu: Option<u16>,
+    mps: Option<u16>,
+) -> PyResult<()> {
+    println!("{}", format!("<<< TCP connection from {}", addr).magenta());
+    println!(
+        "{}",
+        format!(">>> Opening L2CAP channel on PSM = {}", psm).yellow()
+    );
+
+    let mut l2cap_channel = match ble_connection
+        .lock()
+        .await
+        .open_l2cap_channel(psm, max_credits, mtu, mps)
+        .await
+    {
+        Ok(channel) => channel,
+        Err(e) => {
+            println!("{}", format!("!!! Connection failed: {e}").red());
+            // TCP stream will get dropped after returning, automatically shutting it down.
+            return Err(e);
+        }
+    };
+    let channel_info = l2cap_channel
+        .debug_string()
+        .unwrap_or_else(|e| format!("failed to get l2cap channel info ({e})"));
+
+    println!("{}{}", "*** L2CAP channel: ".cyan(), channel_info);
+
+    let (l2cap_to_tcp_tx, l2cap_to_tcp_rx) = mpsc::channel::<BridgeData>(10);
+
+    // Set l2cap callback (`set_sink`) for when data is received.
+    let l2cap_to_tcp_tx_clone = l2cap_to_tcp_tx.clone();
+    l2cap_channel
+        .set_sink(move |_py, sdu| {
+            block_on(l2cap_to_tcp_tx_clone.send(BridgeData::Data(sdu.into())))
+                .expect("failed to channel data to tcp");
+            Ok(())
+        })
+        .expect("failed to set sink for l2cap connection");
+
+    // Set l2cap callback for when the channel is closed.
+    l2cap_channel
+        .on_close(move |_py| {
+            println!("{}", "*** L2CAP channel closed".red());
+            block_on(l2cap_to_tcp_tx.send(BridgeData::CloseSignal))
+                .expect("failed to channel close signal to tcp");
+            Ok(())
+        })
+        .expect("failed to set on_close callback for l2cap channel");
+
+    let l2cap_channel = Arc::new(Mutex::new(Some(l2cap_channel)));
+    let (tcp_reader, tcp_writer) = tcp_stream.into_split();
+
+    // Do tcp stuff when something happens on the l2cap channel.
+    let handle_l2cap_data_future =
+        proxy_l2cap_rx_to_tcp_tx(l2cap_to_tcp_rx, tcp_writer, l2cap_channel.clone());
+
+    // Do l2cap stuff when something happens on tcp.
+    let handle_tcp_data_future = proxy_tcp_rx_to_l2cap_tx(tcp_reader, l2cap_channel.clone(), true);
+
+    let (handle_l2cap_result, handle_tcp_result) =
+        join!(handle_l2cap_data_future, handle_tcp_data_future);
+
+    if let Err(e) = handle_l2cap_result {
+        println!("!!! Error: {e}");
+    }
+
+    if let Err(e) = handle_tcp_result {
+        println!("!!! Error: {e}");
+    }
+
+    Python::with_gil(|_| {
+        // Must hold GIL at least once while/after dropping for Python heap object to ensure
+        // de-allocation.
+        drop(l2cap_channel);
+    });
+
+    Ok(())
+}

rust/src/cli/l2cap/mod.rs

@@ -0,0 +1,190 @@
+// Copyright 2023 Google LLC
+//
+// Licensed under the Apache License, Version 2.0 (the "License");
+// you may not use this file except in compliance with the License.
+// You may obtain a copy of the License at
+//
+//     http://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS,
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// See the License for the specific language governing permissions and
+// limitations under the License.
+
+//! Rust version of the Python `l2cap_bridge.py` found under the `apps` folder.
+
+use crate::L2cap;
+use anyhow::anyhow;
+use bumble::wrapper::{device::Device, l2cap::LeConnectionOrientedChannel, transport::Transport};
+use owo_colors::{colors::css::Orange, OwoColorize};
+use pyo3::{PyObject, PyResult, Python};
+use std::{future::Future, path::PathBuf, sync::Arc};
+use tokio::{
+    io::{AsyncReadExt, AsyncWriteExt},
+    net::tcp::{OwnedReadHalf, OwnedWriteHalf},
+    sync::{mpsc::Receiver, Mutex},
+};
+
+mod client_bridge;
+mod server_bridge;
+
+pub(crate) async fn run(
+    command: L2cap,
+    device_config: PathBuf,
+    transport: String,
+    psm: u16,
+    max_credits: Option<u16>,
+    mtu: Option<u16>,
+    mps: Option<u16>,
+) -> PyResult<()> {
+    println!("<<< connecting to HCI...");
+    let transport = Transport::open(transport).await?;
+    println!("<<< connected");
+
+    let mut device =
+        Device::from_config_file_with_hci(&device_config, transport.source()?, transport.sink()?)?;
+
+    device.power_on().await?;
+
+    match command {
+        L2cap::Server { tcp_host, tcp_port } => {
+            let args = server_bridge::Args {
+                psm,
+                max_credits,
+                mtu,
+                mps,
+                tcp_host,
+                tcp_port,
+            };
+
+            server_bridge::start(&args, &mut device).await?
+        }
+        L2cap::Client {
+            bluetooth_address,
+            tcp_host,
+            tcp_port,
+        } => {
+            let args = client_bridge::Args {
+                psm,
+                max_credits,
+                mtu,
+                mps,
+                bluetooth_address,
+                tcp_host,
+                tcp_port,
+            };
+
+            client_bridge::start(&args, &mut device).await?
+        }
+    };
+
+    // wait until user kills the process
+    tokio::signal::ctrl_c().await?;
+
+    Ok(())
+}
+
+/// Used for channeling data from Python callbacks to a Rust consumer.
+enum BridgeData {
+    Data(Vec<u8>),
+    CloseSignal,
+}
+
+async fn proxy_l2cap_rx_to_tcp_tx(
+    mut l2cap_data_receiver: Receiver<BridgeData>,
+    mut tcp_writer: OwnedWriteHalf,
+    l2cap_channel: Arc<Mutex<Option<LeConnectionOrientedChannel>>>,
+) -> anyhow::Result<()> {
+    while let Some(bridge_data) = l2cap_data_receiver.recv().await {
+        match bridge_data {
+            BridgeData::Data(sdu) => {
+                println!("{}", format!("<<< [L2CAP SDU]: {} bytes", sdu.len()).cyan());
+                tcp_writer
+                    .write_all(sdu.as_ref())
+                    .await
+                    .map_err(|_| anyhow!("Failed to write to tcp stream"))?;
+                tcp_writer
+                    .flush()
+                    .await
+                    .map_err(|_| anyhow!("Failed to flush tcp stream"))?;
+            }
+            BridgeData::CloseSignal => {
+                l2cap_channel.lock().await.take();
+                tcp_writer
+                    .shutdown()
+                    .await
+                    .map_err(|_| anyhow!("Failed to shut down write half of tcp stream"))?;
+                return Ok(());
+            }
+        }
+    }
+    Ok(())
+}
+
+async fn proxy_tcp_rx_to_l2cap_tx(
+    mut tcp_reader: OwnedReadHalf,
+    l2cap_channel: Arc<Mutex<Option<LeConnectionOrientedChannel>>>,
+    drain_l2cap_after_write: bool,
+) -> PyResult<()> {
+    let mut buf = [0; 4096];
+    loop {
+        match tcp_reader.read(&mut buf).await {
+            Ok(len) => {
+                if len == 0 {
+                    println!("{}", "!!! End of stream".fg::<Orange>());
+
+                    if let Some(mut channel) = l2cap_channel.lock().await.take() {
+                        channel.disconnect().await.map_err(|e| {
+                            eprintln!("Failed to call disconnect on l2cap channel: {e}");
+                            e
+                        })?;
+                    }
+                    return Ok(());
+                }
+
+                println!("{}", format!("<<< [TCP DATA]: {len} bytes").blue());
+                match l2cap_channel.lock().await.as_mut() {
+                    None => {
+                        println!("{}", "!!! L2CAP channel not connected, dropping".red());
+                        return Ok(());
+                    }
+                    Some(channel) => {
+                        channel.write(&buf[..len])?;
+                        if drain_l2cap_after_write {
+                            channel.drain().await?;
+                        }
+                    }
+                }
+            }
+            Err(e) => {
+                println!("{}", format!("!!! TCP connection lost: {}", e).red());
+                if let Some(mut channel) = l2cap_channel.lock().await.take() {
+                    let _ = channel.disconnect().await.map_err(|e| {
+                        eprintln!("Failed to call disconnect on l2cap channel: {e}");
+                    });
+                }
+                return Err(e.into());
+            }
+        }
+    }
+}
+
+/// Copies the current thread's TaskLocals into a Python "awaitable" and encapsulates it in a Rust
+/// future, running it as a Python Task.
+/// `TaskLocals` stores the current event loop, and allows the user to copy the current Python
+/// context if necessary. In this case, the python event loop is used when calling `disconnect` on
+/// an l2cap connection, or else the call will fail.
+pub fn run_future_with_current_task_locals<F>(
+    fut: F,
+) -> PyResult<impl Future<Output = PyResult<PyObject>> + Send>
+where
+    F: Future<Output = PyResult<()>> + Send + 'static,
+{
+    Python::with_gil(|py| {
+        let locals = pyo3_asyncio::tokio::get_current_locals(py)?;
+        let future = pyo3_asyncio::tokio::scope(locals.clone(), fut);
+        pyo3_asyncio::tokio::future_into_py_with_locals(py, locals, future)
+            .and_then(pyo3_asyncio::tokio::into_future)
+    })
+}

rust/src/cli/l2cap/server_bridge.rs

@@ -0,0 +1,205 @@
+// Copyright 2023 Google LLC
+//
+// Licensed under the Apache License, Version 2.0 (the "License");
+// you may not use this file except in compliance with the License.
+// You may obtain a copy of the License at
+//
+//     http://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS,
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// See the License for the specific language governing permissions and
+// limitations under the License.
+
+/// L2CAP CoC server bridge: waits for a peer to connect an L2CAP CoC channel
+/// on a specified PSM. When the connection is made, the bridge connects a TCP
+/// socket to a remote host and bridges the data in both directions, with flow
+/// control.
+/// When the L2CAP CoC channel is closed, the bridge disconnects the TCP socket
+/// and waits for a new L2CAP CoC channel to be connected.
+/// When the TCP connection is closed by the TCP server, the L2CAP connection is closed as well.
+use crate::cli::l2cap::{
+    proxy_l2cap_rx_to_tcp_tx, proxy_tcp_rx_to_l2cap_tx, run_future_with_current_task_locals,
+    BridgeData,
+};
+use bumble::wrapper::{device::Device, hci::HciConstant, l2cap::LeConnectionOrientedChannel};
+use futures::executor::block_on;
+use owo_colors::OwoColorize;
+use pyo3::{PyResult, Python};
+use std::{sync::Arc, time::Duration};
+use tokio::{
+    join,
+    net::TcpStream,
+    select,
+    sync::{mpsc, Mutex},
+};
+
+pub struct Args {
+    pub psm: u16,
+    pub max_credits: Option<u16>,
+    pub mtu: Option<u16>,
+    pub mps: Option<u16>,
+    pub tcp_host: String,
+    pub tcp_port: u16,
+}
+
+pub async fn start(args: &Args, device: &mut Device) -> PyResult<()> {
+    let host = args.tcp_host.clone();
+    let port = args.tcp_port;
+    device.register_l2cap_channel_server(
+        args.psm,
+        move |_py, l2cap_channel| {
+            let channel_info = l2cap_channel
+                .debug_string()
+                .unwrap_or_else(|e| format!("failed to get l2cap channel info ({e})"));
+            println!("{} {channel_info}", "*** L2CAP channel:".cyan());
+
+            let host = host.clone();
+            // Ensure Python event loop is available to l2cap `disconnect`
+            let _ = run_future_with_current_task_locals(proxy_data_between_l2cap_and_tcp(
+                l2cap_channel,
+                host,
+                port,
+            ));
+            Ok(())
+        },
+        args.max_credits,
+        args.mtu,
+        args.mps,
+    )?;
+
+    println!(
+        "{}",
+        format!("### Listening for CoC connection on PSM {}", args.psm).yellow()
+    );
+
+    device.on_connection(|_py, mut connection| {
+        let connection_info = connection
+            .debug_string()
+            .unwrap_or_else(|e| format!("failed to get connection info ({e})"));
+        println!(
+            "{} {}",
+            "@@@ Bluetooth connection: ".green(),
+            connection_info,
+        );
+        connection.on_disconnection(|_py, reason| {
+            let disconnection_info = match HciConstant::error_name(reason) {
+                Ok(info_string) => info_string,
+                Err(py_err) => format!("failed to get disconnection error name ({})", py_err),
+            };
+            println!(
+                "{} {}",
+                "@@@ Bluetooth disconnection: ".red(),
+                disconnection_info,
+            );
+            Ok(())
+        })?;
+        Ok(())
+    })?;
+
+    device.start_advertising(false).await?;
+
+    Ok(())
+}
+
+async fn proxy_data_between_l2cap_and_tcp(
+    mut l2cap_channel: LeConnectionOrientedChannel,
+    tcp_host: String,
+    tcp_port: u16,
+) -> PyResult<()> {
+    let (l2cap_to_tcp_tx, mut l2cap_to_tcp_rx) = mpsc::channel::<BridgeData>(10);
+
+    // Set callback (`set_sink`) for when l2cap data is received.
+    let l2cap_to_tcp_tx_clone = l2cap_to_tcp_tx.clone();
+    l2cap_channel
+        .set_sink(move |_py, sdu| {
+            block_on(l2cap_to_tcp_tx_clone.send(BridgeData::Data(sdu.into())))
+                .expect("failed to channel data to tcp");
+            Ok(())
+        })
+        .expect("failed to set sink for l2cap connection");
+
+    // Set l2cap callback for when the channel is closed.
+    l2cap_channel
+        .on_close(move |_py| {
+            println!("{}", "*** L2CAP channel closed".red());
+            block_on(l2cap_to_tcp_tx.send(BridgeData::CloseSignal))
+                .expect("failed to channel close signal to tcp");
+            Ok(())
+        })
+        .expect("failed to set on_close callback for l2cap channel");
+
+    println!(
+        "{}",
+        format!("### Connecting to TCP {tcp_host}:{tcp_port}...").yellow()
+    );
+
+    let l2cap_channel = Arc::new(Mutex::new(Some(l2cap_channel)));
+    let tcp_stream = match TcpStream::connect(format!("{tcp_host}:{tcp_port}")).await {
+        Ok(stream) => {
+            println!("{}", "### Connected".green());
+            Some(stream)
+        }
+        Err(err) => {
+            println!("{}", format!("!!! Connection failed: {err}").red());
+            if let Some(mut channel) = l2cap_channel.lock().await.take() {
+                // Bumble might enter an invalid state if disconnection request is received from
+                // l2cap client before receiving a disconnection response from the same client,
+                // blocking this async call from returning.
+                // See: https://github.com/google/bumble/issues/257
+                select! {
+                    res = channel.disconnect() => {
+                        let _ = res.map_err(|e| eprintln!("Failed to call disconnect on l2cap channel: {e}"));
+                    },
+                    _ = tokio::time::sleep(Duration::from_secs(1)) => eprintln!("Timed out while calling disconnect on l2cap channel."),
+                }
+            }
+            None
+        }
+    };
+
+    match tcp_stream {
+        None => {
+            while let Some(bridge_data) = l2cap_to_tcp_rx.recv().await {
+                match bridge_data {
+                    BridgeData::Data(sdu) => {
+                        println!("{}", format!("<<< [L2CAP SDU]: {} bytes", sdu.len()).cyan());
+                        println!("{}", "!!! TCP socket not open, dropping".red())
+                    }
+                    BridgeData::CloseSignal => break,
+                }
+            }
+        }
+        Some(tcp_stream) => {
+            let (tcp_reader, tcp_writer) = tcp_stream.into_split();
+
+            // Do tcp stuff when something happens on the l2cap channel.
+            let handle_l2cap_data_future =
+                proxy_l2cap_rx_to_tcp_tx(l2cap_to_tcp_rx, tcp_writer, l2cap_channel.clone());
+
+            // Do l2cap stuff when something happens on tcp.
+            let handle_tcp_data_future =
+                proxy_tcp_rx_to_l2cap_tx(tcp_reader, l2cap_channel.clone(), false);
+
+            let (handle_l2cap_result, handle_tcp_result) =
+                join!(handle_l2cap_data_future, handle_tcp_data_future);
+
+            if let Err(e) = handle_l2cap_result {
+                println!("!!! Error: {e}");
+            }
+
+            if let Err(e) = handle_tcp_result {
+                println!("!!! Error: {e}");
+            }
+        }
+    };
+
+    Python::with_gil(|_| {
+        // Must hold GIL at least once while/after dropping for Python heap object to ensure
+        // de-allocation.
+        drop(l2cap_channel);
+    });
+
+    Ok(())
+}

rust/src/cli/mod.rs

@@ -0,0 +1,19 @@
+// Copyright 2023 Google LLC
+//
+// Licensed under the Apache License, Version 2.0 (the "License");
+// you may not use this file except in compliance with the License.
+// You may obtain a copy of the License at
+//
+//     http://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS,
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// See the License for the specific language governing permissions and
+// limitations under the License.
+
+pub(crate) mod firmware;
+
+pub(crate) mod usb;
+
+pub(crate) mod l2cap;

rust/src/cli/usb/mod.rs

@@ -23,7 +23,6 @@
 //! whether it is a Bluetooth device that uses a non-standard Class, or some other
 //! type of device (there's no way to tell).
 
-use clap::Parser as _;
 use itertools::Itertools as _;
 use owo_colors::{OwoColorize, Style};
 use rusb::{Device, DeviceDescriptor, Direction, TransferType, UsbContext};
@@ -31,15 +30,12 @@ use std::{
     collections::{HashMap, HashSet},
     time::Duration,
 };
-
 const USB_DEVICE_CLASS_DEVICE: u8 = 0x00;
 const USB_DEVICE_CLASS_WIRELESS_CONTROLLER: u8 = 0xE0;
 const USB_DEVICE_SUBCLASS_RF_CONTROLLER: u8 = 0x01;
 const USB_DEVICE_PROTOCOL_BLUETOOTH_PRIMARY_CONTROLLER: u8 = 0x01;
 
-fn main() -> anyhow::Result<()> {
-    let cli = Cli::parse();
-
+pub(crate) fn probe(verbose: bool) -> anyhow::Result<()> {
     let mut bt_dev_count = 0;
     let mut device_serials_by_id: HashMap<(u16, u16), HashSet<String>> = HashMap::new();
     for device in rusb::devices()?.iter() {
@@ -159,7 +155,7 @@ fn main() -> anyhow::Result<()> {
             println!("{:26}{}", "  Product:".green(), p);
         }
 
-        if cli.verbose {
+        if verbose {
             print_device_details(&device, &device_desc)?;
         }
 
@@ -332,11 +328,3 @@ impl From<&DeviceDescriptor> for ClassInfo {
         )
     }
 }
-
-#[derive(clap::Parser)]
-#[command(author, version, about, long_about = None)]
-struct Cli {
-    /// Show additional info for each USB device
-    #[arg(long, default_value_t = false)]
-    verbose: bool,
-}

rust/src/internal/drivers/mod.rs

@@ -0,0 +1,17 @@
+// Copyright 2023 Google LLC
+//
+// Licensed under the Apache License, Version 2.0 (the "License");
+// you may not use this file except in compliance with the License.
+// You may obtain a copy of the License at
+//
+//     http://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS,
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// See the License for the specific language governing permissions and
+// limitations under the License.
+
+//! Device drivers
+
+pub(crate) mod rtk;

rust/src/internal/drivers/rtk.rs

@@ -0,0 +1,253 @@
+// Copyright 2023 Google LLC
+//
+// Licensed under the Apache License, Version 2.0 (the "License");
+// you may not use this file except in compliance with the License.
+// You may obtain a copy of the License at
+//
+//     http://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS,
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// See the License for the specific language governing permissions and
+// limitations under the License.
+
+//! Drivers for Realtek controllers
+
+use nom::{bytes, combinator, error, multi, number, sequence};
+
+/// Realtek firmware file contents
+pub struct Firmware {
+    version: u32,
+    project_id: u8,
+    patches: Vec<Patch>,
+}
+
+impl Firmware {
+    /// Parse a `*_fw.bin` file
+    pub fn parse(input: &[u8]) -> Result<Self, nom::Err<error::Error<&[u8]>>> {
+        let extension_sig = [0x51, 0x04, 0xFD, 0x77];
+
+        let (_rem, (_tag, fw_version, patch_count, payload)) =
+            combinator::all_consuming(combinator::map_parser(
+                // ignore the sig suffix
+                sequence::terminated(
+                    bytes::complete::take(
+                        // underflow will show up as parse failure
+                        input.len().saturating_sub(extension_sig.len()),
+                    ),
+                    bytes::complete::tag(extension_sig.as_slice()),
+                ),
+                sequence::tuple((
+                    bytes::complete::tag(b"Realtech"),
+                    // version
+                    number::complete::le_u32,
+                    // patch count
+                    combinator::map(number::complete::le_u16, |c| c as usize),
+                    // everything else except suffix
+                    combinator::rest,
+                )),
+            ))(input)?;
+
+        // ignore remaining input, since patch offsets are relative to the complete input
+        let (_rem, (chip_ids, patch_lengths, patch_offsets)) = sequence::tuple((
+            // chip id
+            multi::many_m_n(patch_count, patch_count, number::complete::le_u16),
+            // patch length
+            multi::many_m_n(patch_count, patch_count, number::complete::le_u16),
+            // patch offset
+            multi::many_m_n(patch_count, patch_count, number::complete::le_u32),
+        ))(payload)?;
+
+        let patches = chip_ids
+            .into_iter()
+            .zip(patch_lengths.into_iter())
+            .zip(patch_offsets.into_iter())
+            .map(|((chip_id, patch_length), patch_offset)| {
+                combinator::map(
+                    sequence::preceded(
+                        bytes::complete::take(patch_offset),
+                        // ignore trailing 4-byte suffix
+                        sequence::terminated(
+                            // patch including svn version, but not suffix
+                            combinator::consumed(sequence::preceded(
+                                // patch before svn version or version suffix
+                                // prefix length underflow will show up as parse failure
+                                bytes::complete::take(patch_length.saturating_sub(8)),
+                                // svn version
+                                number::complete::le_u32,
+                            )),
+                            // dummy suffix, overwritten with firmware version
+                            bytes::complete::take(4_usize),
+                        ),
+                    ),
+                    |(patch_contents_before_version, svn_version): (&[u8], u32)| {
+                        let mut contents = patch_contents_before_version.to_vec();
+                        // replace what would have been the trailing dummy suffix with fw version
+                        contents.extend_from_slice(&fw_version.to_le_bytes());
+
+                        Patch {
+                            contents,
+                            svn_version,
+                            chip_id,
+                        }
+                    },
+                )(input)
+                .map(|(_rem, output)| output)
+            })
+            .collect::<Result<Vec<_>, _>>()?;
+
+        // look for project id from the end
+        let mut offset = payload.len();
+        let mut project_id: Option<u8> = None;
+        while offset >= 2 {
+            // Won't panic, since offset >= 2
+            let chunk = &payload[offset - 2..offset];
+            let length: usize = chunk[0].into();
+            let opcode = chunk[1];
+            offset -= 2;
+
+            if opcode == 0xFF {
+                break;
+            }
+            if length == 0 {
+                // report what nom likely would have done, if nom was good at parsing backwards
+                return Err(nom::Err::Error(error::Error::new(
+                    chunk,
+                    error::ErrorKind::Verify,
+                )));
+            }
+            if opcode == 0 && length == 1 {
+                project_id = offset
+                    .checked_sub(1)
+                    .and_then(|index| payload.get(index))
+                    .copied();
+                break;
+            }
+
+            offset -= length;
+        }
+
+        match project_id {
+            Some(project_id) => Ok(Firmware {
+                project_id,
+                version: fw_version,
+                patches,
+            }),
+            None => {
+                // we ran out of file without finding a project id
+                Err(nom::Err::Error(error::Error::new(
+                    payload,
+                    error::ErrorKind::Eof,
+                )))
+            }
+        }
+    }
+
+    /// Patch version
+    pub fn version(&self) -> u32 {
+        self.version
+    }
+
+    /// Project id
+    pub fn project_id(&self) -> u8 {
+        self.project_id
+    }
+
+    /// Patches
+    pub fn patches(&self) -> &[Patch] {
+        &self.patches
+    }
+}
+
+/// Patch in a [Firmware}
+pub struct Patch {
+    chip_id: u16,
+    contents: Vec<u8>,
+    svn_version: u32,
+}
+
+impl Patch {
+    /// Chip id
+    pub fn chip_id(&self) -> u16 {
+        self.chip_id
+    }
+    /// Contents of the patch, including the 4-byte firmware version suffix
+    pub fn contents(&self) -> &[u8] {
+        &self.contents
+    }
+    /// SVN version
+    pub fn svn_version(&self) -> u32 {
+        self.svn_version
+    }
+}
+
+#[cfg(test)]
+mod tests {
+    use super::*;
+    use anyhow::anyhow;
+    use std::{fs, io, path};
+
+    #[test]
+    fn parse_firmware_rtl8723b() -> anyhow::Result<()> {
+        let fw = Firmware::parse(&firmware_contents("rtl8723b_fw_structure.bin")?)
+            .map_err(|e| anyhow!("{:?}", e))?;
+
+        let fw_version = 0x0E2F9F73;
+        assert_eq!(fw_version, fw.version());
+        assert_eq!(0x0001, fw.project_id());
+        assert_eq!(
+            vec![(0x0001, 0x00002BBF, 22368,), (0x0002, 0x00002BBF, 22496,),],
+            patch_summaries(fw, fw_version)
+        );
+
+        Ok(())
+    }
+
+    #[test]
+    fn parse_firmware_rtl8761bu() -> anyhow::Result<()> {
+        let fw = Firmware::parse(&firmware_contents("rtl8761bu_fw_structure.bin")?)
+            .map_err(|e| anyhow!("{:?}", e))?;
+
+        let fw_version = 0xDFC6D922;
+        assert_eq!(fw_version, fw.version());
+        assert_eq!(0x000E, fw.project_id());
+        assert_eq!(
+            vec![(0x0001, 0x00005060, 14048,), (0x0002, 0xD6D525A4, 30204,),],
+            patch_summaries(fw, fw_version)
+        );
+
+        Ok(())
+    }
+
+    fn firmware_contents(filename: &str) -> io::Result<Vec<u8>> {
+        fs::read(
+            path::PathBuf::from(env!("CARGO_MANIFEST_DIR"))
+                .join("resources/test/firmware/realtek")
+                .join(filename),
+        )
+    }
+
+    /// Return a tuple of (chip id, svn version, contents len, contents sha256)
+    fn patch_summaries(fw: Firmware, fw_version: u32) -> Vec<(u16, u32, usize)> {
+        fw.patches()
+            .iter()
+            .map(|p| {
+                let contents = p.contents();
+                let mut dummy_contents = dummy_contents(contents.len());
+                dummy_contents.extend_from_slice(&p.svn_version().to_le_bytes());
+                dummy_contents.extend_from_slice(&fw_version.to_le_bytes());
+                assert_eq!(&dummy_contents, contents);
+                (p.chip_id(), p.svn_version(), contents.len())
+            })
+            .collect::<Vec<_>>()
+    }
+
+    fn dummy_contents(len: usize) -> Vec<u8> {
+        let mut vec = (len as u32).to_le_bytes().as_slice().repeat(len / 4 + 1);
+        assert!(vec.len() >= len);
+        // leave room for svn version and firmware version
+        vec.truncate(len - 8);
+        vec
+    }
+}

rust/src/internal/mod.rs

@@ -0,0 +1,20 @@
+// Copyright 2023 Google LLC
+//
+// Licensed under the Apache License, Version 2.0 (the "License");
+// you may not use this file except in compliance with the License.
+// You may obtain a copy of the License at
+//
+//     http://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS,
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// See the License for the specific language governing permissions and
+// limitations under the License.
+
+//! It's not clear where to put Rust code that isn't simply a wrapper around Python. Until we have
+//! a good answer for what to do there, the idea is to put it in this (non-public) module, and
+//! `pub use` it into the relevant areas of the `wrapper` module so that it's still easy for users
+//! to discover.
+
+pub(crate) mod drivers;

rust/src/lib.rs

@@ -29,3 +29,5 @@
 pub mod wrapper;
 
 pub mod adv;
+
+pub(crate) mod internal;

rust/src/main.rs

@@ -0,0 +1,271 @@
+// Copyright 2023 Google LLC
+//
+// Licensed under the Apache License, Version 2.0 (the "License");
+// you may not use this file except in compliance with the License.
+// You may obtain a copy of the License at
+//
+//     http://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS,
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// See the License for the specific language governing permissions and
+// limitations under the License.
+
+//! CLI tools for Bumble
+
+#![deny(missing_docs, unsafe_code)]
+
+use bumble::wrapper::logging::{bumble_env_logging_level, py_logging_basic_config};
+use clap::Parser as _;
+use pyo3::PyResult;
+use std::{fmt, path};
+
+mod cli;
+
+#[pyo3_asyncio::tokio::main]
+async fn main() -> PyResult<()> {
+    env_logger::builder()
+        .filter_level(log::LevelFilter::Info)
+        .init();
+
+    py_logging_basic_config(bumble_env_logging_level("INFO"))?;
+
+    let cli: Cli = Cli::parse();
+
+    match cli.subcommand {
+        Subcommand::Firmware { subcommand: fw } => match fw {
+            Firmware::Realtek { subcommand: rtk } => match rtk {
+                Realtek::Download(dl) => {
+                    cli::firmware::rtk::download(dl).await?;
+                }
+                Realtek::Drop { transport } => cli::firmware::rtk::drop(&transport).await?,
+                Realtek::Info { transport, force } => {
+                    cli::firmware::rtk::info(&transport, force).await?;
+                }
+                Realtek::Load { transport, force } => {
+                    cli::firmware::rtk::load(&transport, force).await?
+                }
+                Realtek::Parse { firmware_path } => cli::firmware::rtk::parse(&firmware_path)?,
+            },
+        },
+        Subcommand::L2cap {
+            subcommand,
+            device_config,
+            transport,
+            psm,
+            l2cap_coc_max_credits,
+            l2cap_coc_mtu,
+            l2cap_coc_mps,
+        } => {
+            cli::l2cap::run(
+                subcommand,
+                device_config,
+                transport,
+                psm,
+                l2cap_coc_max_credits,
+                l2cap_coc_mtu,
+                l2cap_coc_mps,
+            )
+            .await?
+        }
+        Subcommand::Usb { subcommand } => match subcommand {
+            Usb::Probe(probe) => cli::usb::probe(probe.verbose)?,
+        },
+    }
+
+    Ok(())
+}
+
+#[derive(clap::Parser)]
+struct Cli {
+    #[clap(subcommand)]
+    subcommand: Subcommand,
+}
+
+#[derive(clap::Subcommand, Debug, Clone)]
+enum Subcommand {
+    /// Manage device firmware
+    Firmware {
+        #[clap(subcommand)]
+        subcommand: Firmware,
+    },
+    /// L2cap client/server operations
+    L2cap {
+        #[command(subcommand)]
+        subcommand: L2cap,
+
+        /// Device configuration file.
+        ///
+        /// See, for instance, `examples/device1.json` in the Python project.
+        #[arg(long)]
+        device_config: path::PathBuf,
+        /// Bumble transport spec.
+        ///
+        /// <https://google.github.io/bumble/transports/index.html>
+        #[arg(long)]
+        transport: String,
+
+        /// PSM for L2CAP Connection-oriented Channel.
+        ///
+        /// Must be in the range [0, 65535].
+        #[arg(long)]
+        psm: u16,
+
+        /// Maximum L2CAP CoC Credits. When not specified, lets Bumble set the default.
+        ///
+        /// Must be in the range [1, 65535].
+        #[arg(long, value_parser = clap::value_parser!(u16).range(1..))]
+        l2cap_coc_max_credits: Option<u16>,
+
+        /// L2CAP CoC MTU. When not specified, lets Bumble set the default.
+        ///
+        /// Must be in the range [23, 65535].
+        #[arg(long, value_parser = clap::value_parser!(u16).range(23..))]
+        l2cap_coc_mtu: Option<u16>,
+
+        /// L2CAP CoC MPS. When not specified, lets Bumble set the default.
+        ///
+        /// Must be in the range [23, 65535].
+        #[arg(long, value_parser = clap::value_parser!(u16).range(23..))]
+        l2cap_coc_mps: Option<u16>,
+    },
+    /// USB operations
+    Usb {
+        #[clap(subcommand)]
+        subcommand: Usb,
+    },
+}
+
+#[derive(clap::Subcommand, Debug, Clone)]
+enum Firmware {
+    /// Manage Realtek chipset firmware
+    Realtek {
+        #[clap(subcommand)]
+        subcommand: Realtek,
+    },
+}
+
+#[derive(clap::Subcommand, Debug, Clone)]
+
+enum Realtek {
+    /// Download Realtek firmware
+    Download(Download),
+    /// Drop firmware from a USB device
+    Drop {
+        /// Bumble transport spec. Must be for a USB device.
+        ///
+        /// <https://google.github.io/bumble/transports/index.html>
+        #[arg(long)]
+        transport: String,
+    },
+    /// Show driver info for a USB device
+    Info {
+        /// Bumble transport spec. Must be for a USB device.
+        ///
+        /// <https://google.github.io/bumble/transports/index.html>
+        #[arg(long)]
+        transport: String,
+        /// Try to resolve driver info even if USB info is not available, or if the USB
+        /// (vendor,product) tuple is not in the list of known compatible RTK USB dongles.
+        #[arg(long, default_value_t = false)]
+        force: bool,
+    },
+    /// Load firmware onto a USB device
+    Load {
+        /// Bumble transport spec. Must be for a USB device.
+        ///
+        /// <https://google.github.io/bumble/transports/index.html>
+        #[arg(long)]
+        transport: String,
+        /// Load firmware even if the USB info doesn't match.
+        #[arg(long, default_value_t = false)]
+        force: bool,
+    },
+    /// Parse a firmware file
+    Parse {
+        /// Firmware file to parse
+        firmware_path: path::PathBuf,
+    },
+}
+
+#[derive(clap::Args, Debug, Clone)]
+struct Download {
+    /// Directory to download to. Defaults to an OS-specific path specific to the Bumble tool.
+    #[arg(long)]
+    output_dir: Option<path::PathBuf>,
+    /// Source to download from
+    #[arg(long, default_value_t = Source::LinuxKernel)]
+    source: Source,
+    /// Only download a single image
+    #[arg(long, value_name = "base name")]
+    single: Option<String>,
+    /// Overwrite existing files
+    #[arg(long, default_value_t = false)]
+    overwrite: bool,
+    /// Don't print the parse results for the downloaded file names
+    #[arg(long)]
+    no_parse: bool,
+}
+
+#[derive(Debug, Clone, clap::ValueEnum)]
+enum Source {
+    LinuxKernel,
+    RealtekOpensource,
+    LinuxFromScratch,
+}
+
+impl fmt::Display for Source {
+    fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
+        match self {
+            Source::LinuxKernel => write!(f, "linux-kernel"),
+            Source::RealtekOpensource => write!(f, "realtek-opensource"),
+            Source::LinuxFromScratch => write!(f, "linux-from-scratch"),
+        }
+    }
+}
+
+#[derive(clap::Subcommand, Debug, Clone)]
+enum L2cap {
+    /// Starts an L2CAP server
+    Server {
+        /// TCP host that the l2cap server will connect to.
+        /// Data is bridged like so:
+        ///     TCP server <-> (TCP client / **L2CAP server**) <-> (L2CAP client / TCP server) <-> TCP client
+        #[arg(long, default_value = "localhost")]
+        tcp_host: String,
+        /// TCP port that the server will connect to.
+        ///
+        /// Must be in the range [1, 65535].
+        #[arg(long, default_value_t = 9544)]
+        tcp_port: u16,
+    },
+    /// Starts an L2CAP client
+    Client {
+        /// L2cap server address that this l2cap client will connect to.
+        bluetooth_address: String,
+        /// TCP host that the l2cap client will bind to and listen for incoming TCP connections.
+        /// Data is bridged like so:
+        ///     TCP client <-> (TCP server / **L2CAP client**) <-> (L2CAP server / TCP client) <-> TCP server
+        #[arg(long, default_value = "localhost")]
+        tcp_host: String,
+        /// TCP port that the client will connect to.
+        ///
+        /// Must be in the range [1, 65535].
+        #[arg(long, default_value_t = 9543)]
+        tcp_port: u16,
+    },
+}
+
+#[derive(clap::Subcommand, Debug, Clone)]
+enum Usb {
+    /// Probe the USB bus for Bluetooth devices
+    Probe(Probe),
+}
+
+#[derive(clap::Args, Debug, Clone)]
+struct Probe {
+    /// Show additional info for each USB device
+    #[arg(long, default_value_t = false)]
+    verbose: bool,
+}

rust/src/wrapper/device.rs

@@ -19,13 +19,19 @@ use crate::{
     wrapper::{
         core::AdvertisingData,
         gatt_client::{ProfileServiceProxy, ServiceProxy},
-        hci::Address,
+        hci::{Address, HciErrorCode},
+        host::Host,
+        l2cap::LeConnectionOrientedChannel,
         transport::{Sink, Source},
-        ClosureCallback,
+        ClosureCallback, PyDictExt, PyObjectExt,
     },
 };
-use pyo3::types::PyDict;
-use pyo3::{intern, types::PyModule, PyObject, PyResult, Python, ToPyObject};
+use pyo3::{
+    intern,
+    types::{PyDict, PyModule},
+    IntoPy, PyObject, PyResult, Python, ToPyObject,
+};
+use pyo3_asyncio::tokio::into_future;
 use std::path;
 
 /// A device that can send/receive HCI frames.
@@ -65,7 +71,7 @@ impl Device {
         Python::with_gil(|py| {
             self.0
                 .call_method0(py, intern!(py, "power_on"))
-                .and_then(|coroutine| pyo3_asyncio::tokio::into_future(coroutine.as_ref(py)))
+                .and_then(|coroutine| into_future(coroutine.as_ref(py)))
         })?
         .await
         .map(|_| ())
@@ -76,12 +82,28 @@ impl Device {
         Python::with_gil(|py| {
             self.0
                 .call_method1(py, intern!(py, "connect"), (peer_addr,))
-                .and_then(|coroutine| pyo3_asyncio::tokio::into_future(coroutine.as_ref(py)))
+                .and_then(|coroutine| into_future(coroutine.as_ref(py)))
         })?
         .await
         .map(Connection)
     }
 
+    /// Register a callback to be called for each incoming connection.
+    pub fn on_connection(
+        &mut self,
+        callback: impl Fn(Python, Connection) -> PyResult<()> + Send + 'static,
+    ) -> PyResult<()> {
+        let boxed = ClosureCallback::new(move |py, args, _kwargs| {
+            callback(py, Connection(args.get_item(0)?.into()))
+        });
+
+        Python::with_gil(|py| {
+            self.0
+                .call_method1(py, intern!(py, "add_listener"), ("connection", boxed))
+        })
+        .map(|_| ())
+    }
+
     /// Start scanning
     pub async fn start_scanning(&self, filter_duplicates: bool) -> PyResult<()> {
         Python::with_gil(|py| {
@@ -89,7 +111,7 @@ impl Device {
             kwargs.set_item("filter_duplicates", filter_duplicates)?;
             self.0
                 .call_method(py, intern!(py, "start_scanning"), (), Some(kwargs))
-                .and_then(|coroutine| pyo3_asyncio::tokio::into_future(coroutine.as_ref(py)))
+                .and_then(|coroutine| into_future(coroutine.as_ref(py)))
         })?
         .await
         .map(|_| ())
@@ -123,6 +145,15 @@ impl Device {
         .map(|_| ())
     }
 
+    /// Returns the host used by the device, if any
+    pub fn host(&mut self) -> PyResult<Option<Host>> {
+        Python::with_gil(|py| {
+            self.0
+                .getattr(py, intern!(py, "host"))
+                .map(|obj| obj.into_option(Host::from))
+        })
+    }
+
     /// Start advertising the data set with [Device.set_advertisement].
     pub async fn start_advertising(&mut self, auto_restart: bool) -> PyResult<()> {
         Python::with_gil(|py| {
@@ -131,7 +162,7 @@ impl Device {
 
             self.0
                 .call_method(py, intern!(py, "start_advertising"), (), Some(kwargs))
-                .and_then(|coroutine| pyo3_asyncio::tokio::into_future(coroutine.as_ref(py)))
+                .and_then(|coroutine| into_future(coroutine.as_ref(py)))
         })?
         .await
         .map(|_| ())
@@ -142,16 +173,114 @@ impl Device {
         Python::with_gil(|py| {
             self.0
                 .call_method0(py, intern!(py, "stop_advertising"))
-                .and_then(|coroutine| pyo3_asyncio::tokio::into_future(coroutine.as_ref(py)))
+                .and_then(|coroutine| into_future(coroutine.as_ref(py)))
         })?
         .await
         .map(|_| ())
     }
+
+    /// Registers an L2CAP connection oriented channel server. When a client connects to the server,
+    /// the `server` callback is passed a handle to the established channel. When optional arguments
+    /// are not specified, the Python module specifies the defaults.
+    pub fn register_l2cap_channel_server(
+        &mut self,
+        psm: u16,
+        server: impl Fn(Python, LeConnectionOrientedChannel) -> PyResult<()> + Send + 'static,
+        max_credits: Option<u16>,
+        mtu: Option<u16>,
+        mps: Option<u16>,
+    ) -> PyResult<()> {
+        Python::with_gil(|py| {
+            let boxed = ClosureCallback::new(move |py, args, _kwargs| {
+                server(
+                    py,
+                    LeConnectionOrientedChannel::from(args.get_item(0)?.into()),
+                )
+            });
+
+            let kwargs = PyDict::new(py);
+            kwargs.set_item("psm", psm)?;
+            kwargs.set_item("server", boxed.into_py(py))?;
+            kwargs.set_opt_item("max_credits", max_credits)?;
+            kwargs.set_opt_item("mtu", mtu)?;
+            kwargs.set_opt_item("mps", mps)?;
+            self.0.call_method(
+                py,
+                intern!(py, "register_l2cap_channel_server"),
+                (),
+                Some(kwargs),
+            )
+        })?;
+        Ok(())
+    }
 }
 
 /// A connection to a remote device.
 pub struct Connection(PyObject);
 
+impl Connection {
+    /// Open an L2CAP channel using this connection. When optional arguments are not specified, the
+    /// Python module specifies the defaults.
+    pub async fn open_l2cap_channel(
+        &mut self,
+        psm: u16,
+        max_credits: Option<u16>,
+        mtu: Option<u16>,
+        mps: Option<u16>,
+    ) -> PyResult<LeConnectionOrientedChannel> {
+        Python::with_gil(|py| {
+            let kwargs = PyDict::new(py);
+            kwargs.set_item("psm", psm)?;
+            kwargs.set_opt_item("max_credits", max_credits)?;
+            kwargs.set_opt_item("mtu", mtu)?;
+            kwargs.set_opt_item("mps", mps)?;
+            self.0
+                .call_method(py, intern!(py, "open_l2cap_channel"), (), Some(kwargs))
+                .and_then(|coroutine| pyo3_asyncio::tokio::into_future(coroutine.as_ref(py)))
+        })?
+        .await
+        .map(LeConnectionOrientedChannel::from)
+    }
+
+    /// Disconnect from device with provided reason. When optional arguments are not specified, the
+    /// Python module specifies the defaults.
+    pub async fn disconnect(&mut self, reason: Option<HciErrorCode>) -> PyResult<()> {
+        Python::with_gil(|py| {
+            let kwargs = PyDict::new(py);
+            kwargs.set_opt_item("reason", reason)?;
+            self.0
+                .call_method(py, intern!(py, "disconnect"), (), Some(kwargs))
+                .and_then(|coroutine| pyo3_asyncio::tokio::into_future(coroutine.as_ref(py)))
+        })?
+        .await
+        .map(|_| ())
+    }
+
+    /// Register a callback to be called on disconnection.
+    pub fn on_disconnection(
+        &mut self,
+        callback: impl Fn(Python, HciErrorCode) -> PyResult<()> + Send + 'static,
+    ) -> PyResult<()> {
+        let boxed = ClosureCallback::new(move |py, args, _kwargs| {
+            callback(py, args.get_item(0)?.extract()?)
+        });
+
+        Python::with_gil(|py| {
+            self.0
+                .call_method1(py, intern!(py, "add_listener"), ("disconnection", boxed))
+        })
+        .map(|_| ())
+    }
+
+    /// Returns some information about the connection as a [String].
+    pub fn debug_string(&self) -> PyResult<String> {
+        Python::with_gil(|py| {
+            let str_obj = self.0.call_method0(py, intern!(py, "__str__"))?;
+            str_obj.gil_ref(py).extract()
+        })
+    }
+}
+
 /// The other end of a connection
 pub struct Peer(PyObject);
 
@@ -173,7 +302,7 @@ impl Peer {
         Python::with_gil(|py| {
             self.0
                 .call_method0(py, intern!(py, "discover_services"))
-                .and_then(|coroutine| pyo3_asyncio::tokio::into_future(coroutine.as_ref(py)))
+                .and_then(|coroutine| into_future(coroutine.as_ref(py)))
         })?
         .await
         .and_then(|list| {
@@ -207,13 +336,7 @@ impl Peer {
             let class = module.getattr(P::PROXY_CLASS_NAME)?;
             self.0
                 .call_method1(py, intern!(py, "create_service_proxy"), (class,))
-                .map(|obj| {
-                    if obj.is_none(py) {
-                        None
-                    } else {
-                        Some(P::wrap(obj))
-                    }
-                })
+                .map(|obj| obj.into_option(P::wrap))
         })
     }
 }

rust/src/wrapper/drivers/mod.rs

@@ -0,0 +1,17 @@
+// Copyright 2023 Google LLC
+//
+// Licensed under the Apache License, Version 2.0 (the "License");
+// you may not use this file except in compliance with the License.
+// You may obtain a copy of the License at
+//
+//     http://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS,
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// See the License for the specific language governing permissions and
+// limitations under the License.
+
+//! Device drivers
+
+pub mod rtk;

rust/src/wrapper/drivers/rtk.rs

@@ -0,0 +1,141 @@
+// Copyright 2023 Google LLC
+//
+// Licensed under the Apache License, Version 2.0 (the "License");
+// you may not use this file except in compliance with the License.
+// You may obtain a copy of the License at
+//
+//     http://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS,
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// See the License for the specific language governing permissions and
+// limitations under the License.
+
+//! Drivers for Realtek controllers
+
+use crate::wrapper::{host::Host, PyObjectExt};
+use pyo3::{intern, types::PyModule, PyObject, PyResult, Python, ToPyObject};
+use pyo3_asyncio::tokio::into_future;
+
+pub use crate::internal::drivers::rtk::{Firmware, Patch};
+
+/// Driver for a Realtek controller
+pub struct Driver(PyObject);
+
+impl Driver {
+    /// Locate the driver for the provided host.
+    pub async fn for_host(host: &Host, force: bool) -> PyResult<Option<Self>> {
+        Python::with_gil(|py| {
+            PyModule::import(py, intern!(py, "bumble.drivers.rtk"))?
+                .getattr(intern!(py, "Driver"))?
+                .call_method1(intern!(py, "for_host"), (&host.obj, force))
+                .and_then(into_future)
+        })?
+        .await
+        .map(|obj| obj.into_option(Self))
+    }
+
+    /// Check if the host has a known driver.
+    pub async fn check(host: &Host) -> PyResult<bool> {
+        Python::with_gil(|py| {
+            PyModule::import(py, intern!(py, "bumble.drivers.rtk"))?
+                .getattr(intern!(py, "Driver"))?
+                .call_method1(intern!(py, "check"), (&host.obj,))
+                .and_then(|obj| obj.extract::<bool>())
+        })
+    }
+
+    /// Find the [DriverInfo] for the host, if one matches
+    pub async fn driver_info_for_host(host: &Host) -> PyResult<Option<DriverInfo>> {
+        Python::with_gil(|py| {
+            PyModule::import(py, intern!(py, "bumble.drivers.rtk"))?
+                .getattr(intern!(py, "Driver"))?
+                .call_method1(intern!(py, "driver_info_for_host"), (&host.obj,))
+                .and_then(into_future)
+        })?
+        .await
+        .map(|obj| obj.into_option(DriverInfo))
+    }
+
+    /// Send a command to the device to drop firmware
+    pub async fn drop_firmware(host: &mut Host) -> PyResult<()> {
+        Python::with_gil(|py| {
+            PyModule::import(py, intern!(py, "bumble.drivers.rtk"))?
+                .getattr(intern!(py, "Driver"))?
+                .call_method1(intern!(py, "drop_firmware"), (&host.obj,))
+                .and_then(into_future)
+        })?
+        .await
+        .map(|_| ())
+    }
+
+    /// Load firmware onto the device.
+    pub async fn download_firmware(&mut self) -> PyResult<()> {
+        Python::with_gil(|py| {
+            self.0
+                .call_method0(py, intern!(py, "download_firmware"))
+                .and_then(|coroutine| into_future(coroutine.as_ref(py)))
+        })?
+        .await
+        .map(|_| ())
+    }
+}
+
+/// Metadata about a known driver & applicable device
+pub struct DriverInfo(PyObject);
+
+impl DriverInfo {
+    /// Returns a list of all drivers that Bumble knows how to handle.
+    pub fn all_drivers() -> PyResult<Vec<DriverInfo>> {
+        Python::with_gil(|py| {
+            PyModule::import(py, intern!(py, "bumble.drivers.rtk"))?
+                .getattr(intern!(py, "Driver"))?
+                .getattr(intern!(py, "DRIVER_INFOS"))?
+                .iter()?
+                .map(|r| r.map(|h| DriverInfo(h.to_object(py))))
+                .collect::<PyResult<Vec<_>>>()
+        })
+    }
+
+    /// The firmware file name to load from the filesystem, e.g. `foo_fw.bin`.
+    pub fn firmware_name(&self) -> PyResult<String> {
+        Python::with_gil(|py| {
+            self.0
+                .getattr(py, intern!(py, "fw_name"))?
+                .as_ref(py)
+                .extract::<String>()
+        })
+    }
+
+    /// The config file name, if any, to load from the filesystem, e.g. `foo_config.bin`.
+    pub fn config_name(&self) -> PyResult<Option<String>> {
+        Python::with_gil(|py| {
+            let obj = self.0.getattr(py, intern!(py, "config_name"))?;
+            let handle = obj.as_ref(py);
+
+            if handle.is_none() {
+                Ok(None)
+            } else {
+                handle
+                    .extract::<String>()
+                    .map(|s| if s.is_empty() { None } else { Some(s) })
+            }
+        })
+    }
+
+    /// Whether or not config is required.
+    pub fn config_needed(&self) -> PyResult<bool> {
+        Python::with_gil(|py| {
+            self.0
+                .getattr(py, intern!(py, "config_needed"))?
+                .as_ref(py)
+                .extract::<bool>()
+        })
+    }
+
+    /// ROM id
+    pub fn rom(&self) -> PyResult<u32> {
+        Python::with_gil(|py| self.0.getattr(py, intern!(py, "rom"))?.as_ref(py).extract())
+    }
+}

rust/src/wrapper/hci.rs

@@ -15,7 +15,40 @@
 //! HCI
 
 use itertools::Itertools as _;
-use pyo3::{exceptions::PyException, intern, types::PyModule, PyErr, PyObject, PyResult, Python};
+use pyo3::{
+    exceptions::PyException, intern, types::PyModule, FromPyObject, PyAny, PyErr, PyObject,
+    PyResult, Python, ToPyObject,
+};
+
+/// HCI error code.
+pub struct HciErrorCode(u8);
+
+impl<'source> FromPyObject<'source> for HciErrorCode {
+    fn extract(ob: &'source PyAny) -> PyResult<Self> {
+        Ok(HciErrorCode(ob.extract()?))
+    }
+}
+
+impl ToPyObject for HciErrorCode {
+    fn to_object(&self, py: Python<'_>) -> PyObject {
+        self.0.to_object(py)
+    }
+}
+
+/// Provides helpers for interacting with HCI
+pub struct HciConstant;
+
+impl HciConstant {
+    /// Human-readable error name
+    pub fn error_name(status: HciErrorCode) -> PyResult<String> {
+        Python::with_gil(|py| {
+            PyModule::import(py, intern!(py, "bumble.hci"))?
+                .getattr(intern!(py, "HCI_Constant"))?
+                .call_method1(intern!(py, "error_name"), (status.0,))?
+                .extract()
+        })
+    }
+}
 
 /// A Bluetooth address
 pub struct Address(pub(crate) PyObject);

rust/src/wrapper/host.rs

@@ -0,0 +1,71 @@
+// Copyright 2023 Google LLC
+//
+// Licensed under the Apache License, Version 2.0 (the "License");
+// you may not use this file except in compliance with the License.
+// You may obtain a copy of the License at
+//
+//     http://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS,
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// See the License for the specific language governing permissions and
+// limitations under the License.
+
+//! Host-side types
+
+use crate::wrapper::transport::{Sink, Source};
+use pyo3::{intern, prelude::PyModule, types::PyDict, PyObject, PyResult, Python};
+
+/// Host HCI commands
+pub struct Host {
+    pub(crate) obj: PyObject,
+}
+
+impl Host {
+    /// Create a Host that wraps the provided obj
+    pub(crate) fn from(obj: PyObject) -> Self {
+        Self { obj }
+    }
+
+    /// Create a new Host
+    pub fn new(source: Source, sink: Sink) -> PyResult<Self> {
+        Python::with_gil(|py| {
+            PyModule::import(py, intern!(py, "bumble.host"))?
+                .getattr(intern!(py, "Host"))?
+                .call((source.0, sink.0), None)
+                .map(|any| Self { obj: any.into() })
+        })
+    }
+
+    /// Send a reset command and perform other reset tasks.
+    pub async fn reset(&mut self, driver_factory: DriverFactory) -> PyResult<()> {
+        Python::with_gil(|py| {
+            let kwargs = match driver_factory {
+                DriverFactory::None => {
+                    let kw = PyDict::new(py);
+                    kw.set_item("driver_factory", py.None())?;
+                    Some(kw)
+                }
+                DriverFactory::Auto => {
+                    // leave the default in place
+                    None
+                }
+            };
+            self.obj
+                .call_method(py, intern!(py, "reset"), (), kwargs)
+                .and_then(|coroutine| pyo3_asyncio::tokio::into_future(coroutine.as_ref(py)))
+        })?
+        .await
+        .map(|_| ())
+    }
+}
+
+/// Driver factory to use when initializing a host
+#[derive(Debug, Clone)]
+pub enum DriverFactory {
+    /// Do not load drivers
+    None,
+    /// Load appropriate driver, if any is found
+    Auto,
+}

rust/src/wrapper/l2cap.rs

@@ -0,0 +1,92 @@
+// Copyright 2023 Google LLC
+//
+// Licensed under the Apache License, Version 2.0 (the "License");
+// you may not use this file except in compliance with the License.
+// You may obtain a copy of the License at
+//
+//     http://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS,
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// See the License for the specific language governing permissions and
+// limitations under the License.
+
+//! L2CAP
+
+use crate::wrapper::{ClosureCallback, PyObjectExt};
+use pyo3::{intern, PyObject, PyResult, Python};
+
+/// L2CAP connection-oriented channel
+pub struct LeConnectionOrientedChannel(PyObject);
+
+impl LeConnectionOrientedChannel {
+    /// Create a LeConnectionOrientedChannel that wraps the provided obj.
+    pub(crate) fn from(obj: PyObject) -> Self {
+        Self(obj)
+    }
+
+    /// Queues data to be automatically sent across this channel.
+    pub fn write(&mut self, data: &[u8]) -> PyResult<()> {
+        Python::with_gil(|py| self.0.call_method1(py, intern!(py, "write"), (data,))).map(|_| ())
+    }
+
+    /// Wait for queued data to be sent on this channel.
+    pub async fn drain(&mut self) -> PyResult<()> {
+        Python::with_gil(|py| {
+            self.0
+                .call_method0(py, intern!(py, "drain"))
+                .and_then(|coroutine| pyo3_asyncio::tokio::into_future(coroutine.as_ref(py)))
+        })?
+        .await
+        .map(|_| ())
+    }
+
+    /// Register a callback to be called when the channel is closed.
+    pub fn on_close(
+        &mut self,
+        callback: impl Fn(Python) -> PyResult<()> + Send + 'static,
+    ) -> PyResult<()> {
+        let boxed = ClosureCallback::new(move |py, _args, _kwargs| callback(py));
+
+        Python::with_gil(|py| {
+            self.0
+                .call_method1(py, intern!(py, "add_listener"), ("close", boxed))
+        })
+        .map(|_| ())
+    }
+
+    /// Register a callback to be called when the channel receives data.
+    pub fn set_sink(
+        &mut self,
+        callback: impl Fn(Python, &[u8]) -> PyResult<()> + Send + 'static,
+    ) -> PyResult<()> {
+        let boxed = ClosureCallback::new(move |py, args, _kwargs| {
+            callback(py, args.get_item(0)?.extract()?)
+        });
+        Python::with_gil(|py| self.0.setattr(py, intern!(py, "sink"), boxed)).map(|_| ())
+    }
+
+    /// Disconnect the l2cap channel.
+    /// Must be called from a thread with a Python event loop, which should be true on
+    /// `tokio::main` and `async_std::main`.
+    ///
+    /// For more info, see https://awestlake87.github.io/pyo3-asyncio/master/doc/pyo3_asyncio/#event-loop-references-and-contextvars.
+    pub async fn disconnect(&mut self) -> PyResult<()> {
+        Python::with_gil(|py| {
+            self.0
+                .call_method0(py, intern!(py, "disconnect"))
+                .and_then(|coroutine| pyo3_asyncio::tokio::into_future(coroutine.as_ref(py)))
+        })?
+        .await
+        .map(|_| ())
+    }
+
+    /// Returns some information about the channel as a [String].
+    pub fn debug_string(&self) -> PyResult<String> {
+        Python::with_gil(|py| {
+            let str_obj = self.0.call_method0(py, intern!(py, "__str__"))?;
+            str_obj.gil_ref(py).extract()
+        })
+    }
+}

rust/src/wrapper/mod.rs

@@ -31,14 +31,17 @@ pub use pyo3_asyncio;
 pub mod assigned_numbers;
 pub mod core;
 pub mod device;
+pub mod drivers;
 pub mod gatt_client;
 pub mod hci;
+pub mod host;
+pub mod l2cap;
 pub mod logging;
 pub mod profile;
 pub mod transport;
 
 /// Convenience extensions to [PyObject]
-pub trait PyObjectExt {
+pub trait PyObjectExt: Sized {
     /// Get a GIL-bound reference
     fn gil_ref<'py>(&'py self, py: Python<'py>) -> &'py PyAny;
 
@@ -49,6 +52,17 @@ pub trait PyObjectExt {
     {
         Python::with_gil(|py| self.gil_ref(py).extract::<T>())
     }
+
+    /// If the Python object is a Python `None`, return a Rust `None`, otherwise `Some` with the mapped type
+    fn into_option<T>(self, map_obj: impl Fn(Self) -> T) -> Option<T> {
+        Python::with_gil(|py| {
+            if self.gil_ref(py).is_none() {
+                None
+            } else {
+                Some(map_obj(self))
+            }
+        })
+    }
 }
 
 impl PyObjectExt for PyObject {
@@ -57,6 +71,21 @@ impl PyObjectExt for PyObject {
     }
 }
 
+/// Convenience extensions to [PyDict]
+pub trait PyDictExt {
+    /// Set item in dict only if value is Some, otherwise do nothing.
+    fn set_opt_item<K: ToPyObject, V: ToPyObject>(&self, key: K, value: Option<V>) -> PyResult<()>;
+}
+
+impl PyDictExt for PyDict {
+    fn set_opt_item<K: ToPyObject, V: ToPyObject>(&self, key: K, value: Option<V>) -> PyResult<()> {
+        if let Some(value) = value {
+            self.set_item(key, value)?
+        }
+        Ok(())
+    }
+}
+
 /// Wrapper to make Rust closures ([Fn] implementations) callable from Python.
 ///
 /// The Python callable form returns a Python `None`.

rust/src/wrapper/profile.rs

@@ -14,7 +14,10 @@
 
 //! GATT profiles
 
-use crate::wrapper::gatt_client::{CharacteristicProxy, ProfileServiceProxy};
+use crate::wrapper::{
+    gatt_client::{CharacteristicProxy, ProfileServiceProxy},
+    PyObjectExt,
+};
 use pyo3::{intern, PyObject, PyResult, Python};
 
 /// Exposes the battery GATT service
@@ -26,13 +29,7 @@ impl BatteryServiceProxy {
         Python::with_gil(|py| {
             self.0
                 .getattr(py, intern!(py, "battery_level"))
-                .map(|level| {
-                    if level.is_none(py) {
-                        None
-                    } else {
-                        Some(CharacteristicProxy(level))
-                    }
-                })
+                .map(|level| level.into_option(CharacteristicProxy))
         })
     }
 }

setup.cfg

@@ -40,6 +40,7 @@ install_requires =
     humanize >= 4.6.0; platform_system!='Emscripten'
     libusb1 >= 2.0.1; platform_system!='Emscripten'
     libusb-package == 1.0.26.1; platform_system!='Emscripten'
+    platformdirs == 3.10.0; platform_system!='Emscripten'
     prompt_toolkit >= 3.0.16; platform_system!='Emscripten'
     prettytable >= 3.6.0; platform_system!='Emscripten'
     protobuf >= 3.12.4; platform_system!='Emscripten'

tools/rtk_fw_download.py

@@ -67,8 +67,9 @@ def download_file(base_url, name, remove_suffix):
 @click.command
 @click.option(
     "--output-dir",
-    default=".",
-    help="Output directory where the files will be saved",
+    default="",
+    help="Output directory where the files will be saved. Defaults to the OS-specific"
+    "app data dir, which the driver will check when trying to find firmware",
     show_default=True,
 )
 @click.option(
@@ -84,7 +85,10 @@ def main(output_dir, source, single, force, parse):
     """Download RTK firmware images and configs."""
 
     # Check that the output dir exists
-    output_dir = pathlib.Path(output_dir)
+    if output_dir == '':
+        output_dir = rtk.rtk_firmware_dir()
+    else:
+        output_dir = pathlib.Path(output_dir)
     if not output_dir.is_dir():
         print("Output dir does not exist or is not a directory")
         return

tools/rtk_util.py

@@ -61,9 +61,8 @@ async def do_load(usb_transport, force):
         # Get the driver.
         driver = await rtk.Driver.for_host(host, force)
         if driver is None:
-            if not force:
-                print("Firmware already loaded or no supported driver for this device.")
-                return
+            print("Firmware already loaded or no supported driver for this device.")
+            return
 
         await driver.download_firmware()