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    SubjectRe: [PATCH v9 16/22] media: uvcvideo: Return -EACCES to inactive controls
    Hi Ricardo,

    Thank you for the patch.

    On Fri, Mar 26, 2021 at 10:58:34AM +0100, Ricardo Ribalda 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.

    Isn't the device supposed to stall the control set in that case, with
    the bRequestErrorCode set to "Wrong state", which uvc_query_ctrl()
    translates to -EACCES already ? Could you elaborate on why this patch is
    needed ?

    > Suggested-by: Hans Verkuil <hverkuil-cisco@xs4all.nl>
    > Signed-off-by: Ricardo Ribalda <ribalda@chromium.org>
    > ---
    > drivers/media/usb/uvc/uvc_ctrl.c | 71 +++++++++++++++++++++-----------
    > 1 file changed, 48 insertions(+), 23 deletions(-)
    >
    > diff --git a/drivers/media/usb/uvc/uvc_ctrl.c b/drivers/media/usb/uvc/uvc_ctrl.c
    > index bcebf9d1a46f..d9d4add1e813 100644
    > --- a/drivers/media/usb/uvc/uvc_ctrl.c
    > +++ b/drivers/media/usb/uvc/uvc_ctrl.c
    > @@ -1082,13 +1082,36 @@ 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;
    >
    > @@ -1104,18 +1127,8 @@ 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;

    There's a small change in behaviour here, the driver used to return an
    error, now it will ignore it. Is it intentional ?

    > -
    > - 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);
    > @@ -1638,25 +1651,37 @@ static int uvc_ctrl_commit_entity(struct uvc_device *dev,
    > return 0;
    > }
    >
    > -static int uvc_ctrl_find_ctrlidx(struct uvc_entity *entity,
    > +static int uvc_ctrl_commit_error(struct uvc_video_chain *chain,
    > + struct uvc_entity *entity,
    > struct v4l2_ext_controls *ctrls,
    > - struct uvc_control *uvc_control)
    > + 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;

    I think this line should be moved after the next check.

    > +
    > + /* We could not find the control that failed. */
    > + if (i == ctrls->count)
    > + return ret;
    >
    > - return ctrls->count;
    > + if (uvc_ctrl_is_inactive(chain, err_control, mapping))
    > + return -EACCES;
    > +
    > + return ret;
    > }
    >
    > int __uvc_ctrl_commit(struct uvc_fh *handle, int rollback,
    > @@ -1679,8 +1704,8 @@ 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_ctrlidx(entity, ctrls,
    > - err_ctrl);
    > + ret = uvc_ctrl_commit_error(chain, entity, ctrls, err_ctrl,
    > + ret);
    > mutex_unlock(&chain->ctrl_mutex);
    > return ret;
    > }

    --
    Regards,

    Laurent Pinchart

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