[v2] usb: gadget: uvc: Expose configuration name through video node

[Laurent Pinchart <laurent.pinchart@ideasonboard.com>]

Hi Kieran,

Thank you for the patch.

On Thursday, 24 May 2018 19:16:12 EEST Kieran Bingham wrote:
> From: Kieran Bingham <kieran.bingham@ideasonboard.com>
> 
> 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.
> 
> Signed-off-by: Kieran Bingham <kieran.bingham@ideasonboard.com>

Reviewed-by: Laurent Pinchart <laurent.pinchart@ideasonboard.com>

> ---
> v2:
>  - Fix commit title (f_uvc -> uvc)
>  - Change identifier file name (now function_name)
>  - Document in ABI
> 
>  .../ABI/testing/configfs-usb-gadget-uvc       |  5 ++++
>  drivers/usb/gadget/function/f_uvc.c           | 24 ++++++++++++++++++-
>  2 files changed, 28 insertions(+), 1 deletion(-)
> 
> diff --git a/Documentation/ABI/testing/configfs-usb-gadget-uvc
> b/Documentation/ABI/testing/configfs-usb-gadget-uvc index
> 1ba0d0fda9c0..9281e2aa38df 100644
> --- 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/
functio
> n_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 d82cd61676d3..c8627cc698f8
> 100644
> --- a/drivers/usb/gadget/function/f_uvc.c
> +++ b/drivers/usb/gadget/function/f_uvc.c
> @@ -421,10 +421,21 @@ 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;
> @@ -437,7 +448,17 @@ 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) \
> @@ -877,6 +898,7 @@ 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);