jtag/drivers/cmsis_dap: introduce packet_usable_size

USB bulk backend needs to avoid zero sized USB packets
sent after each full sized packed for performance reasons.

HID backend uses fixed size HID reports so the full size
of the report can be utilized.

Introduce packet_usable_size to reflect it.

Signed-off-by: Tomas Vanek <vanekt@fbl.cz>
Change-Id: I34094c9edac5730624480711cbd6aa65883c47c7
Reviewed-on: https://review.openocd.org/c/openocd/+/7363
Tested-by: jenkins
Reviewed-by: Antonio Borneo <borneo.antonio@gmail.com>

4 files changed, 8 insertions, 12 deletions

diff --git a/src/jtag/drivers/cmsis_dap.c b/src/jtag/drivers/cmsis_dap.c
index 5e01d06..364a177 100644
--- a/src/jtag/drivers/cmsis_dap.c
+++ b/src/jtag/drivers/cmsis_dap.c
@@ -229,7 +229,7 @@ static int pending_scan_result_count;
 static struct pending_scan_result pending_scan_results[MAX_PENDING_SCAN_RESULTS];
 
 /* queued JTAG sequences that will be executed on the next flush */
-#define QUEUED_SEQ_BUF_LEN (cmsis_dap_handle->packet_size - 3)
+#define QUEUED_SEQ_BUF_LEN (cmsis_dap_handle->packet_usable_size - 3)
 static int queued_seq_count;
 static int queued_seq_buf_end;
 static int queued_seq_tdo_ptr;
diff --git a/src/jtag/drivers/cmsis_dap.h b/src/jtag/drivers/cmsis_dap.h
index 8004419..72e07fb 100644
--- a/src/jtag/drivers/cmsis_dap.h
+++ b/src/jtag/drivers/cmsis_dap.h
@@ -27,6 +27,7 @@ struct cmsis_dap {
 	struct cmsis_dap_backend_data *bdata;
 	const struct cmsis_dap_backend *backend;
 	unsigned int packet_size;
+	unsigned int packet_usable_size;
 	unsigned int packet_buffer_size;
 	uint8_t *packet_buffer;
 	uint8_t *command;
diff --git a/src/jtag/drivers/cmsis_dap_usb_bulk.c b/src/jtag/drivers/cmsis_dap_usb_bulk.c
index 55b9a55..6599c41 100644
--- a/src/jtag/drivers/cmsis_dap_usb_bulk.c
+++ b/src/jtag/drivers/cmsis_dap_usb_bulk.c
@@ -352,25 +352,17 @@ static int cmsis_dap_usb_open(struct cmsis_dap *dap, uint16_t vids[], uint16_t p
 				return ERROR_FAIL;
 			}
 
-			dap->packet_size = packet_size;
-			dap->packet_buffer_size = packet_size;
 			dap->bdata->usb_ctx = ctx;
 			dap->bdata->dev_handle = dev_handle;
 			dap->bdata->ep_out = ep_out;
 			dap->bdata->ep_in = ep_in;
 			dap->bdata->interface = interface_num;
 
-			dap->packet_buffer = malloc(dap->packet_buffer_size);
-			if (!dap->packet_buffer) {
-				LOG_ERROR("unable to allocate memory");
+			err = cmsis_dap_usb_alloc(dap, packet_size);
+			if (err != ERROR_OK)
 				cmsis_dap_usb_close(dap);
-				return ERROR_FAIL;
-			}
-
-			dap->command = dap->packet_buffer;
-			dap->response = dap->packet_buffer;
 
-			return ERROR_OK;
+			return err;
 		}
 
 		libusb_close(dev_handle);
@@ -445,6 +437,8 @@ static int cmsis_dap_usb_alloc(struct cmsis_dap *dap, unsigned int pkt_sz)
 	dap->packet_buffer = buf;
 	dap->packet_size = pkt_sz;
 	dap->packet_buffer_size = pkt_sz;
+	/* Prevent sending zero size USB packets */
+	dap->packet_usable_size = pkt_sz - 1;
 
 	dap->command = dap->packet_buffer;
 	dap->response = dap->packet_buffer;
diff --git a/src/jtag/drivers/cmsis_dap_usb_hid.c b/src/jtag/drivers/cmsis_dap_usb_hid.c
index 592eb09..52dfd76 100644
--- a/src/jtag/drivers/cmsis_dap_usb_hid.c
+++ b/src/jtag/drivers/cmsis_dap_usb_hid.c
@@ -213,6 +213,7 @@ static int cmsis_dap_hid_alloc(struct cmsis_dap *dap, unsigned int pkt_sz)
 
 	dap->packet_buffer = buf;
 	dap->packet_size = pkt_sz;
+	dap->packet_usable_size = pkt_sz;
 	dap->packet_buffer_size = packet_buffer_size;
 
 	dap->command = dap->packet_buffer + REPORT_ID_SIZE;