On 07/22/2015 06:14 PM, Sakari Ailus wrote: > By default, serialise open and release internal ops using a mutex. > > The underlying problem is that a large proportion of the drivers do use
Well, the only one I found that does this is the flash-led-class :-) But you are correct in your reply to my comments that the lock has to be taken in v4l2-subdev.c and not in the driver. <snip> > +static void subdev_open_lock(struct v4l2_subdev *sd) > +{ > + if (sd->flags & V4L2_SUBDEV_FL_SERIALISE_OPEN) > + mutex_lock(&sd->open_lock); > +} > + > +static void subdev_open_unlock(struct v4l2_subdev *sd) > +{ > + if (sd->flags & V4L2_SUBDEV_FL_SERIALISE_OPEN) > + mutex_unlock(&sd->open_lock); > +} I really dislike this flag. Also, I think there are more problems here since none of the ioctls are serialized so you depend on the driver to get that right. My suggestion would be to add a struct mutex *lock pointer to struct v4l2_subdev, and, if non-NULL, then take that lock for both open/close and ioctls (you take the lock in subdev_ioctl()). This is similar to struct video_device and you don't need a flag. In addition, drivers can provide their own lock. Regards, Hans -- To unsubscribe from this list: send the line "unsubscribe linux-media" in the body of a message to majord...@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html