usb: gadget: uvc: Expose configuration name through video node

When utilising multiple instantiations of a UVC gadget on a composite
device, there is no clear method to link a particular configuration to
its respective video node.

Provide a means for identifying the correct video node by exposing the
name of the function configuration through sysfs.

Reviewed-by: Laurent Pinchart <laurent.pinchart@ideasonboard.com>
Signed-off-by: Kieran Bingham <kieran.bingham@ideasonboard.com>
Signed-off-by: Felipe Balbi <felipe.balbi@linux.intel.com>

diff --git a/Documentation/ABI/testing/configfs-usb-gadget-uvc b/Documentation/ABI/testing/configfs-usb-gadget-uvc
index 1ba0d0f..9281e2a 100644 (file)
--- a/Documentation/ABI/testing/configfs-usb-gadget-uvc
+++ b/Documentation/ABI/testing/configfs-usb-gadget-uvc
@@ -263,3 +263,8 @@ Description:        Specific streaming header descriptors
                                        is connected
                bmInfo                  - capabilities of this video streaming
                                        interface
+
+What:          /sys/class/udc/udc.name/device/gadget/video4linux/video.name/function_name
+Date:          May 2018
+KernelVersion: 4.19
+Description:   UVC configfs function instance name

diff --git a/drivers/usb/gadget/function/f_uvc.c b/drivers/usb/gadget/function/f_uvc.c
index 1d2feac..d8ce786 100644 (file)
--- a/drivers/usb/gadget/function/f_uvc.c
+++ b/drivers/usb/gadget/function/f_uvc.c
@@ -413,10 +413,21 @@ uvc_function_disconnect(struct uvc_device *uvc)
  * USB probe and disconnect
  */
 
+static ssize_t function_name_show(struct device *dev,
+                                 struct device_attribute *attr, char *buf)
+{
+       struct uvc_device *uvc = dev_get_drvdata(dev);
+
+       return sprintf(buf, "%s\n", uvc->func.fi->group.cg_item.ci_name);
+}
+
+static DEVICE_ATTR_RO(function_name);
+
 static int
 uvc_register_video(struct uvc_device *uvc)
 {
        struct usb_composite_dev *cdev = uvc->func.config->cdev;
+       int ret;
 
        /* TODO reference counting. */
        uvc->vdev.v4l2_dev = &uvc->v4l2_dev;
@@ -429,7 +440,17 @@ uvc_register_video(struct uvc_device *uvc)
 
        video_set_drvdata(&uvc->vdev, uvc);
 
-       return video_register_device(&uvc->vdev, VFL_TYPE_GRABBER, -1);
+       ret = video_register_device(&uvc->vdev, VFL_TYPE_GRABBER, -1);
+       if (ret < 0)
+               return ret;
+
+       ret = device_create_file(&uvc->vdev.dev, &dev_attr_function_name);
+       if (ret < 0) {
+               video_unregister_device(&uvc->vdev);
+               return ret;
+       }
+
+       return 0;
 }
 
 #define UVC_COPY_DESCRIPTOR(mem, dst, desc) \
@@ -867,6 +888,7 @@ static void uvc_unbind(struct usb_configuration *c, struct usb_function *f)
 
        INFO(cdev, "%s\n", __func__);
 
+       device_remove_file(&uvc->vdev.dev, &dev_attr_function_name);
        video_unregister_device(&uvc->vdev);
        v4l2_device_unregister(&uvc->v4l2_dev);