hla: add ability to configure read/write buffer size

Other adapters (TI ICDI) that use this driver can use a larger
read/write buffer size than the original stlink could.

Change-Id: I9beb7748049097cbe29a2340799c450bd74e199d
Signed-off-by: Spencer Oliver <spen@spen-soft.co.uk>
Reviewed-on: http://openocd.zylin.com/948
Tested-by: jenkins

src/jtag/hla/hla_interface.c

@@ -37,7 +37,7 @@
 
 #include <target/target.h>
 
-static struct hl_interface_s hl_if = { {0, 0, 0, 0, 0, 0}, 0, 0 };
+static struct hl_interface_s hl_if = { {0, 0, 0, 0, 0, 0, 0}, 0, 0 };
 
 int hl_interface_open(enum hl_transports tr)
 {

src/jtag/hla/hla_interface.h

@@ -44,6 +44,8 @@ struct hl_interface_param_s {
 	unsigned api;
 	/** */
 	enum hl_transports transport;
+	/** */
+	int max_buffer;
 };
 
 struct hl_interface_s {

src/jtag/hla/hla_layout.c

@@ -50,6 +50,12 @@ static int hl_layout_open(struct hl_interface_s *adapter)
 		return res;
 	}
 
+	/* make sure adapter has set the buffer size */
+	if (!adapter->param.max_buffer) {
+		LOG_ERROR("buffer size not set");
+		return ERROR_FAIL;
+	}
+
 	return ERROR_OK;
 }