Re: [PATCH] media: uvcvideo: Fix uvc_ctrl_fixup_xu_info() not having any effect

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

Hi Hans,

Thank you for the patch.

On Fri, Jul 24, 2020 at 01:48:23PM +0200, Hans de Goede wrote:
> uvc_ctrl_add_info() calls uvc_ctrl_get_flags() which will override
> the fixed-up flags set by uvc_ctrl_fixup_xu_info().
> 
> This commit fixes this by adding a is_xu argument to uvc_ctrl_add_info()
> and skipping the uvc_ctrl_get_flags() call for xu ctrls.
> 
> Note that the xu path has already called uvc_ctrl_get_flags() from
> uvc_ctrl_fill_xu_info() before calling uvc_ctrl_add_info().
> 
> This fixes the xu motor controls not working properly on a Logitech
> 046d:08cc, and presumably also on the other Logitech models which have
> a quirk for this in the uvc_ctrl_fixup_xu_info() function.
> 
> Cc: stable@vger.kernel.org
> Signed-off-by: Hans de Goede <hdegoede@redhat.com>
> ---
>  drivers/media/usb/uvc/uvc_ctrl.c | 11 ++++++-----
>  1 file changed, 6 insertions(+), 5 deletions(-)
> 
> diff --git a/drivers/media/usb/uvc/uvc_ctrl.c b/drivers/media/usb/uvc/uvc_ctrl.c
> index e399b9fad757..4bdea5814d6a 100644
> --- a/drivers/media/usb/uvc/uvc_ctrl.c
> +++ b/drivers/media/usb/uvc/uvc_ctrl.c
> @@ -1815,7 +1815,7 @@ static int uvc_ctrl_fill_xu_info(struct uvc_device *dev,
>  }
>  
>  static int uvc_ctrl_add_info(struct uvc_device *dev, struct uvc_control *ctrl,
> -	const struct uvc_control_info *info);
> +	const struct uvc_control_info *info, bool is_xu);
>  
>  static int uvc_ctrl_init_xu_ctrl(struct uvc_device *dev,
>  	struct uvc_control *ctrl)
> @@ -1830,7 +1830,7 @@ static int uvc_ctrl_init_xu_ctrl(struct uvc_device *dev,
>  	if (ret < 0)
>  		return ret;
>  
> -	ret = uvc_ctrl_add_info(dev, ctrl, &info);
> +	ret = uvc_ctrl_add_info(dev, ctrl, &info, true);
>  	if (ret < 0)
>  		uvc_trace(UVC_TRACE_CONTROL, "Failed to initialize control "
>  			  "%pUl/%u on device %s entity %u\n", info.entity,
> @@ -2009,7 +2009,7 @@ int uvc_ctrl_restore_values(struct uvc_device *dev)
>   * Add control information to a given control.
>   */
>  static int uvc_ctrl_add_info(struct uvc_device *dev, struct uvc_control *ctrl,
> -	const struct uvc_control_info *info)
> +	const struct uvc_control_info *info, bool is_xu)
>  {
>  	int ret = 0;
>  
> @@ -2029,7 +2029,8 @@ static int uvc_ctrl_add_info(struct uvc_device *dev, struct uvc_control *ctrl,
>  	 * default flag values from the uvc_ctrl array when the device doesn't
>  	 * properly implement GET_INFO on standard controls.
>  	 */
> -	uvc_ctrl_get_flags(dev, ctrl, &ctrl->info);
> +	if (!is_xu)
> +		uvc_ctrl_get_flags(dev, ctrl, &ctrl->info);

Would it make sense to instead move this line (and the above comment) to
uvc_ctrl_init_ctrl(), right after the uvc_ctrl_add_info() call ? If you
would prefer keeping it here, I think is_xu should be renamed to
update_flags (with the true/false values switched) to make it clearer.
It would then also add a comment to uvc_ctrl_init_xu_ctrl() right before
the call to uvc_ctrl_add_info() to state that we don't update flags to
avoid overwriting the value set by uvc_ctrl_fixup_xu_info() in
uvc_ctrl_fill_xu_info().

What's your preference ?

>  
>  	ctrl->initialized = 1;
>  
> @@ -2252,7 +2253,7 @@ static void uvc_ctrl_init_ctrl(struct uvc_device *dev, struct uvc_control *ctrl)
>  	for (; info < iend; ++info) {
>  		if (uvc_entity_match_guid(ctrl->entity, info->entity) &&
>  		    ctrl->index == info->index) {
> -			uvc_ctrl_add_info(dev, ctrl, info);
> +			uvc_ctrl_add_info(dev, ctrl, info, false);
>  			break;
>  		 }
>  	}

-- 
Regards,

Laurent Pinchart