uvc_ctrl_commit() not rolling back / restoring UVC_CTRL_DATA_BACKUP of not yet processed entities on errors

[Hans de Goede <hdegoede@xxxxxxxxxx>]

Hi All,

While reviewing Ricardo's "[PATCH v4 0/4] media: uvcvideo: Two fixes for
async controls" series I noticed that uvc_ctrl_commit() stops processing
entities on an error:

	list_for_each_entry(entity, &chain->entities, chain) {
		ret = uvc_ctrl_commit_entity(chain->dev, entity, rollback,
					     &err_ctrl);
		if (ret < 0) {
			if (ctrls)
				ctrls->error_idx =
					uvc_ctrl_find_ctrl_idx(entity, ctrls,
							       err_ctrl);
			goto done;
		}
	}

This means that if there are further entities with changed ctrls
in the chain, not only do the new ctrl values not get committed
which is expected. But the new values do get kept in the drivers
cached ctrl values.

I believe that what needs to happen instead is that the loop
over all entities is continued, but for the other entities
uvc_ctrl_commit_entity() needs to be called with rollback = 1
after the error.

Regards,

Hans