Re: [PATCH v10 21/21] media: uvcvideo: Return -EACCES to inactive controls

[Ricardo Ribalda <ribalda@chromium.org>]

Hi Hans

Did you have some hardware that did not work fine without this patch?
Am I remembering correctly?

Thanks!

On Fri, 18 Jun 2021 at 14:29, Ricardo Ribalda <ribalda@chromium.org> wrote:
>
> If a control is inactive return -EACCES to let the userspace know that
> the value will not be applied automatically when the control is active
> again.
>
> Also make sure that query_v4l2_ctrl doesn't return an error.
>
> Suggested-by: Hans Verkuil <hverkuil-cisco@xs4all.nl>
> Reviewed-by: Hans Verkuil <hverkuil-cisco@xs4all.nl>
> Signed-off-by: Ricardo Ribalda <ribalda@chromium.org>
> ---
>  drivers/media/usb/uvc/uvc_ctrl.c | 73 +++++++++++++++++++++-----------
>  1 file changed, 49 insertions(+), 24 deletions(-)
>
> diff --git a/drivers/media/usb/uvc/uvc_ctrl.c b/drivers/media/usb/uvc/uvc_ctrl.c
> index da44d5c0b9ad..4f80c06d3c43 100644
> --- a/drivers/media/usb/uvc/uvc_ctrl.c
> +++ b/drivers/media/usb/uvc/uvc_ctrl.c
> @@ -1104,13 +1104,36 @@ static const char *uvc_map_get_name(const struct uvc_control_mapping *map)
>         return "Unknown Control";
>  }
>
> +static bool uvc_ctrl_is_inactive(struct uvc_video_chain *chain,
> +                                struct uvc_control *ctrl,
> +                                struct uvc_control_mapping *mapping)
> +{
> +       struct uvc_control_mapping *master_map = NULL;
> +       struct uvc_control *master_ctrl = NULL;
> +       s32 val;
> +       int ret;
> +
> +       if (!mapping->master_id)
> +               return false;
> +
> +       __uvc_find_control(ctrl->entity, mapping->master_id, &master_map,
> +                          &master_ctrl, 0);
> +
> +       if (!master_ctrl || !(master_ctrl->info.flags & UVC_CTRL_FLAG_GET_CUR))
> +               return false;
> +
> +       ret = __uvc_ctrl_get(chain, master_ctrl, master_map, &val);
> +       if (ret < 0 || val == mapping->master_manual)
> +               return false;
> +
> +       return true;
> +}
> +
>  static int __uvc_query_v4l2_ctrl(struct uvc_video_chain *chain,
>         struct uvc_control *ctrl,
>         struct uvc_control_mapping *mapping,
>         struct v4l2_queryctrl *v4l2_ctrl)
>  {
> -       struct uvc_control_mapping *master_map = NULL;
> -       struct uvc_control *master_ctrl = NULL;
>         const struct uvc_menu_info *menu;
>         unsigned int i;
>
> @@ -1126,18 +1149,8 @@ static int __uvc_query_v4l2_ctrl(struct uvc_video_chain *chain,
>         if (!(ctrl->info.flags & UVC_CTRL_FLAG_SET_CUR))
>                 v4l2_ctrl->flags |= V4L2_CTRL_FLAG_READ_ONLY;
>
> -       if (mapping->master_id)
> -               __uvc_find_control(ctrl->entity, mapping->master_id,
> -                                  &master_map, &master_ctrl, 0);
> -       if (master_ctrl && (master_ctrl->info.flags & UVC_CTRL_FLAG_GET_CUR)) {
> -               s32 val;
> -               int ret = __uvc_ctrl_get(chain, master_ctrl, master_map, &val);
> -               if (ret < 0)
> -                       return ret;
> -
> -               if (val != mapping->master_manual)
> -                               v4l2_ctrl->flags |= V4L2_CTRL_FLAG_INACTIVE;
> -       }
> +       if (uvc_ctrl_is_inactive(chain, ctrl, mapping))
> +               v4l2_ctrl->flags |= V4L2_CTRL_FLAG_INACTIVE;
>
>         if (!ctrl->cached) {
>                 int ret = uvc_ctrl_populate_cache(chain, ctrl);
> @@ -1660,25 +1673,37 @@ static int uvc_ctrl_commit_entity(struct uvc_device *dev,
>         return 0;
>  }
>
> -static int uvc_ctrl_find_ctrl_idx(struct uvc_entity *entity,
> -                                 struct v4l2_ext_controls *ctrls,
> -                                 struct uvc_control *uvc_control)
> +static int uvc_ctrl_commit_error(struct uvc_video_chain *chain,
> +                                struct uvc_entity *entity,
> +                                struct v4l2_ext_controls *ctrls,
> +                                struct uvc_control *err_control,
> +                                int ret)
>  {
>         struct uvc_control_mapping *mapping;
>         struct uvc_control *ctrl_found;
>         unsigned int i;
>
> -       if (!entity)
> -               return ctrls->count;
> +       if (!entity) {
> +               ctrls->error_idx = ctrls->count;
> +               return ret;
> +       }
>
>         for (i = 0; i < ctrls->count; i++) {
>                 __uvc_find_control(entity, ctrls->controls[i].id, &mapping,
>                                    &ctrl_found, 0);
> -               if (uvc_control == ctrl_found)
> -                       return i;
> +               if (err_control == ctrl_found)
> +                       break;
>         }
> +       ctrls->error_idx = i;
> +
> +       /* We could not find the control that failed. */
> +       if (i == ctrls->count)
> +               return ret;
> +
> +       if (uvc_ctrl_is_inactive(chain, err_control, mapping))
> +               return -EACCES;
>
> -       return ctrls->count;
> +       return ret;
>  }
>
>  int __uvc_ctrl_commit(struct uvc_fh *handle, int rollback,
> @@ -1701,8 +1726,8 @@ int __uvc_ctrl_commit(struct uvc_fh *handle, int rollback,
>                 uvc_ctrl_send_events(handle, ctrls->controls, ctrls->count);
>  done:
>         if (ret < 0 && ctrls)
> -               ctrls->error_idx = uvc_ctrl_find_ctrl_idx(entity, ctrls,
> -                                                         err_ctrl);
> +               ret = uvc_ctrl_commit_error(chain, entity, ctrls, err_ctrl,
> +                                           ret);
>         mutex_unlock(&chain->ctrl_mutex);
>         return ret;
>  }
> --
> 2.32.0.288.g62a8d224e6-goog
>


-- 
Ricardo Ribalda