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

On 25/06/2021 12:29, Ricardo Ribalda wrote:

Hi Hans

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

Yes, that's correct. It's one of my webcams, but I can't remember which one
it is. You probably want me to test this v10?

Regards,

	Hans

Thanks!

On Fri, 18 Jun 2021 at 14:29, Ricardo Ribalda [off-list ref] wrote:

quoted

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 <redacted>
Reviewed-by: Hans Verkuil <redacted>
Signed-off-by: Ricardo Ribalda <redacted>
---
 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