Re: [PATCH v8 3/3] uvcvideo: handle control pipe protocol STALLs

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

Hi Guennadi,

Thank you for the patch.

On Tuesday, 8 May 2018 18:07:44 EEST Guennadi Liakhovetski wrote:
> When a command ends up in a STALL on the control pipe, use the Request
> Error Code control to provide a more precise error information to the
> user. For example, if a camera is still busy processing a control,
> when the same or an interrelated control set request arrives, the
> camera can react with a STALL and then return the "Not ready" status
> in response to a UVC_VC_REQUEST_ERROR_CODE_CONTROL command. With this
> patch the user would then get an EBUSY error code instead of a
> generic EPIPE.
> 
> Signed-off-by: Guennadi Liakhovetski <guennadi.liakhovetski@intel.com>

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

> ---
> 
> v8:
> 
> * restrict UVC_VC_REQUEST_ERROR_CODE_CONTROL to the control interface
> * fix the wIndex value
> * improve error codes
> * cosmetic changes
> 
>  drivers/media/usb/uvc/uvc_video.c | 52 +++++++++++++++++++++++++++++++-----
>  1 file changed, 46 insertions(+), 6 deletions(-)
> 
> diff --git a/drivers/media/usb/uvc/uvc_video.c
> b/drivers/media/usb/uvc/uvc_video.c index aa0082f..ce65cd6 100644
> --- a/drivers/media/usb/uvc/uvc_video.c
> +++ b/drivers/media/usb/uvc/uvc_video.c
> @@ -73,17 +73,57 @@ int uvc_query_ctrl(struct uvc_device *dev, u8 query, u8
> unit, u8 intfnum, u8 cs, void *data, u16 size)
>  {
>  	int ret;
> +	u8 error;
> +	u8 tmp;
> 
>  	ret = __uvc_query_ctrl(dev, query, unit, intfnum, cs, data, size,
>  				UVC_CTRL_CONTROL_TIMEOUT);
> -	if (ret != size) {
> -		uvc_printk(KERN_ERR, "Failed to query (%s) UVC control %u on "
> -			"unit %u: %d (exp. %u).\n", uvc_query_name(query), cs,
> -			unit, ret, size);
> -		return -EIO;
> +	if (likely(ret == size))
> +		return 0;
> +
> +	uvc_printk(KERN_ERR,
> +		   "Failed to query (%s) UVC control %u on unit %u: %d (exp. %u).\n",
> +		   uvc_query_name(query), cs, unit, ret, size);
> +
> +	if (ret != -EPIPE)
> +		return ret;
> +
> +	tmp = *(u8 *)data;
> +
> +	ret = __uvc_query_ctrl(dev, UVC_GET_CUR, 0, intfnum,
> +			       UVC_VC_REQUEST_ERROR_CODE_CONTROL, data, 1,
> +			       UVC_CTRL_CONTROL_TIMEOUT);
> +
> +	error = *(u8 *)data;
> +	*(u8 *)data = tmp;
> +
> +	if (ret != 1)
> +		return ret < 0 ? ret : -EPIPE;
> +
> +	uvc_trace(UVC_TRACE_CONTROL, "Control error %u\n", error);
> +
> +	switch (error) {
> +	case 0:
> +		/* Cannot happen - we received a STALL */
> +		return -EPIPE;
> +	case 1: /* Not ready */
> +		return -EBUSY;
> +	case 2: /* Wrong state */
> +		return -EILSEQ;
> +	case 3: /* Power */
> +		return -EREMOTE;
> +	case 4: /* Out of range */
> +		return -ERANGE;
> +	case 5: /* Invalid unit */
> +	case 6: /* Invalid control */
> +	case 7: /* Invalid Request */
> +	case 8: /* Invalid value within range */
> +		return -EINVAL;
> +	default: /* reserved or unknown */
> +		break;
>  	}
> 
> -	return 0;
> +	return -EPIPE;
>  }
> 
>  static void uvc_fixup_video_ctrl(struct uvc_streaming *stream,

-- 
Regards,

Laurent Pinchart