rlink: read only the expected number of bytes

After correcting the reply size counter, it should be safe to rely on it
for the number of bytes expected in the USB read, instead of reading the
endpoint maximum. This doesn't make things go any faster but it's nicer and
removes the local buffer.

Signed-off-by: Andreas Fritiofson <andreas.fritiofson@gmail.com>

src/jtag/drivers/rlink.c

@@ -500,7 +500,7 @@ dtc_run_download(
 		uint8_t	*reply_buffer,
 		int	reply_buffer_size
 ) {
-	uint8_t	ep2_buffer[USB_EP2IN_SIZE];
+	char dtc_status;
 	int	usb_err;
 	int	i;
 
@@ -530,12 +530,12 @@ dtc_run_download(
 		usb_err = usb_bulk_read(
 				pHDev_param,
 				USB_EP1IN_ADDR,
-				(char *)ep2_buffer, 1,
+				&dtc_status, 1,
 				USB_TIMEOUT_MS
 		);
 		if (usb_err < 0) return(usb_err);
 
-		if (ep2_buffer[0] & 0x01) break;
+		if (dtc_status & 0x01) break;
 
 		if (!--i) {
 			LOG_ERROR("too many retries waiting for DTC status");
@@ -544,24 +544,20 @@ dtc_run_download(
 	}
 
 
-	if (!reply_buffer) reply_buffer_size = 0;
-	if (reply_buffer_size) {
+	if (reply_buffer && reply_buffer_size) {
 		usb_err = usb_bulk_read(
 				pHDev_param,
 				USB_EP2IN_ADDR,
-				(char *)ep2_buffer, sizeof(ep2_buffer),
+				(char *)reply_buffer, reply_buffer_size,
 				USB_TIMEOUT_MS
 		);
 
-		if (usb_err < (int)sizeof(ep2_buffer)) {
+		if (usb_err < reply_buffer_size) {
 			LOG_ERROR("Read of endpoint 2 returned %d, expected %d",
 					usb_err, reply_buffer_size
 			);
 			return(usb_err);
 		}
-
-		memcpy(reply_buffer, ep2_buffer, reply_buffer_size);
-
 	}
 
 	return(usb_err);