Add convenience function to find and open a device by USB VID+PID

Lots of libusb apps I write are simple test apps not intended to be real
apps. Having a function available to quickly locate my device will be
handy in such situations.

diff --git a/examples/dpfp.c b/examples/dpfp.c
index 87a7da1..6b5124e 100644 (file)
--- a/examples/dpfp.c
+++ b/examples/dpfp.c
@@ -81,36 +81,8 @@ static struct libusb_bulk_transfer irqtrf = {
 
 static int find_dpfp_device(void)
 {
-       struct libusb_device *dev;
-       struct libusb_device *found = NULL;
-       struct libusb_device **devs;
-       size_t i = 0;
-       int r;
-
-       r = libusb_get_device_list(&devs);
-       if (r < 0)
-               return r;
-
-       while ((dev = devs[i++]) != NULL) {
-               struct libusb_dev_descriptor *desc = libusb_device_get_descriptor(dev);
-               if (desc->idVendor == 0x05ba && desc->idProduct == 0x000a) {
-                       found = dev;
-                       break;
-               }
-       }
-
-       if (!found) {
-               r = -ENODEV;
-               goto out;
-       }
-
-       devh = libusb_open(dev);
-       if (!devh)
-               r = -EIO;
-
-out:
-       libusb_free_device_list(devs, 1);
-       return r;
+       devh = libusb_open_device_with_vid_pid(0x05ba, 0x000a);
+       return devh ? 0 : -EIO;
 }
 
 static int print_f0_data(void)

diff --git a/libusb/core.c b/libusb/core.c
index cd01515..a366c8c 100644 (file)
--- a/libusb/core.c
+++ b/libusb/core.c
@@ -385,6 +385,37 @@ API_EXPORTED struct libusb_dev_handle *libusb_open(struct libusb_device *dev)
        return devh;
 }
 
+/* convenience function for finding a device with a particular vendor/product
+ * combination. has limitations and is hence not intended for use in "real
+ * applications": if multiple devices have the same VID+PID it'll only
+ * give you the first one, etc. */
+API_EXPORTED struct libusb_dev_handle *libusb_open_device_with_vid_pid(
+       uint16_t vendor_id, uint16_t product_id)
+{
+       struct libusb_device **devs;
+       struct libusb_device *found = NULL;
+       struct libusb_device *dev;
+       struct libusb_dev_handle *devh;
+       size_t i = 0;
+
+       if (libusb_get_device_list(&devs) < 0)
+               return NULL;
+
+       while ((dev = devs[i++]) != NULL) {
+               struct libusb_dev_descriptor *desc = libusb_device_get_descriptor(dev);
+               if (desc->idVendor == vendor_id && desc->idProduct == product_id) {
+                       found = dev;
+                       break;
+               }
+       }
+
+       if (found)
+               devh = libusb_open(found);
+
+       libusb_free_device_list(devs, 1);
+       return devh;
+}
+
 static void do_close(struct libusb_dev_handle *devh)
 {
        usbi_remove_pollfd(devh->fd);

diff --git a/libusb/libusb.h b/libusb/libusb.h
index cddc232..4e1bc14 100644 (file)
--- a/libusb/libusb.h
+++ b/libusb/libusb.h
@@ -231,10 +231,13 @@ void libusb_device_unref(libusb_device *dev);
 
 libusb_dev_handle *libusb_open(libusb_device *dev);
 void libusb_close(libusb_dev_handle *devh);
-struct libusb_device *libusb_devh_get_device(libusb_dev_handle *devh);
+libusb_device *libusb_devh_get_device(libusb_dev_handle *devh);
 int libusb_claim_interface(libusb_dev_handle *dev, int iface);
 int libusb_release_interface(libusb_dev_handle *dev, int iface);
 
+libusb_dev_handle *libusb_open_device_with_vid_pid(uint16_t vendor_id,
+       uint16_t product_id);
+
 /* async I/O */
 
 libusb_urb_handle *libusb_async_control_transfer(libusb_dev_handle *devh,