cmsis-dap: prevent hidapi to search again for the adapter

The code in cmsis_dap_usb_open() already searches for the right
HID device that corresponds to the adapter. By calling hid_open()
it asks hidapi to re-search the adapter again based on the VID:PID
and the serial string of the adapter it has just found!

Apart from being a run-time overhead, this has an additional
drawback; there are USB adapters built as composite USB devices
that, beside the cmsis-dap HID interface, have other HID
interfaces for other purposes.
A typical example is the NXP LPC-Link2, that over the 5 interfaces
	0) cmsis-dap (HID)
	1) VCOM-CDC
	2) VCOM-CDC
	3) LPCSIO (HID)
	4) LPC-LINK2 DATA PORT (HID)
has 3 of them of HID class.
The code in cmsis_dap_usb_open() could select the right interface
but then cannot propagate this information to hid_open().

Replace the call to hid_open() with hid_open_path(), passing as
parameter the "unique" path of the HID device already found.

Checking in hidapi source code, the implementation of hid_open()
consists in enumerating the HID devices, scan for the first one
matching VID:PID and serial number, and opening it by calling
hid_open_path(). This analysis highlights that using directly
hid_open_path() should not introduce any regression.

While applying these changes, move hid_init() before enumerating
the HID devices. This has no real consequences because the HID API
is marked as optional but, logically, it should be called before
any other HID API.

Change-Id: I77ec01dca64223ec597f21f188f363366d0049c6
Signed-off-by: Antonio Borneo <borneo.antonio@gmail.com>
Suggested-by: Masatoshi Tateishi <tateishim3@gmail.com>
Reviewed-on: http://openocd.zylin.com/5731
Tested-by: jenkins

1 files changed, 8 insertions, 14 deletions

diff --git a/src/jtag/drivers/cmsis_dap_usb.c b/src/jtag/drivers/cmsis_dap_usb.c
index ee1cb53..8915836 100644
--- a/src/jtag/drivers/cmsis_dap_usb.c
+++ b/src/jtag/drivers/cmsis_dap_usb.c
@@ -229,14 +229,16 @@ static int cmsis_dap_usb_open(void)
 	int i;
 	struct hid_device_info *devs, *cur_dev;
 	unsigned short target_vid, target_pid;
-	wchar_t *target_serial = NULL;
-
 	bool found = false;
-	bool serial_found = false;
 
 	target_vid = 0;
 	target_pid = 0;
 
+	if (hid_init() != 0) {
+		LOG_ERROR("unable to open HIDAPI");
+		return ERROR_FAIL;
+	}
+
 	/*
 	 * The CMSIS-DAP specification stipulates:
 	 * "The Product String must contain "CMSIS-DAP" somewhere in the string. This is used by the
@@ -273,7 +275,6 @@ static int cmsis_dap_usb_open(void)
 			/* check serial number matches if given */
 			if (cmsis_dap_serial != NULL) {
 				if ((cur_dev->serial_number != NULL) && wcscmp(cmsis_dap_serial, cur_dev->serial_number) == 0) {
-					serial_found = true;
 					break;
 				}
 			} else
@@ -288,23 +289,16 @@ static int cmsis_dap_usb_open(void)
 	if (NULL != cur_dev) {
 		target_vid = cur_dev->vendor_id;
 		target_pid = cur_dev->product_id;
-		if (serial_found)
-			target_serial = cmsis_dap_serial;
 	}
 
-	hid_free_enumeration(devs);
-
 	if (target_vid == 0 && target_pid == 0) {
 		LOG_ERROR("unable to find CMSIS-DAP device");
+		hid_free_enumeration(devs);
 		return ERROR_FAIL;
 	}
 
-	if (hid_init() != 0) {
-		LOG_ERROR("unable to open HIDAPI");
-		return ERROR_FAIL;
-	}
-
-	dev = hid_open(target_vid, target_pid, target_serial);
+	dev = hid_open_path(cur_dev->path);
+	hid_free_enumeration(devs);
 
 	if (dev == NULL) {
 		LOG_ERROR("unable to open CMSIS-DAP device 0x%x:0x%x", target_vid, target_pid);