On 10/25/2012 02:42 PM, Sylwester Nawrocki wrote: > Hi Laurent, > > On 10/25/2012 01:35 PM, Laurent Pinchart wrote: >> On Thursday 25 October 2012 11:06:56 Sylwester Nawrocki wrote: >>> Make sure there is no v4l2_device_unregister_subdev() call >>> on a subdev which wasn't registered. >> >> I'm not implying that this fix is bad, but doesn't the V4L2 core already >> handle this ? v4l2_device_unregister_subdev() returns immediately without >> doing anything if the subdev hasn't been registered. > > Indeed, the patch summary might be a bit misleading and incomplete. > I of course wanted to make sure the platform subdevs are not treated > as registered when any part of v4l2_device_register_subdev() fails. > > > Looking at function v4l2_device_register_subdev(), I'm wondering whether > line > 159 sd->v4l2_dev = v4l2_dev; > > shouldn't be moved right before > > 190 spin_lock(&v4l2_dev->lock); > > so sd->v4l2_dev is set only if we return 0 in this function ? Hmm, no, that would be wrong. Since sd->v4l2_dev needs to be initialized for sd->internal_ops->registered() and sd->internal_ops->registered() ops. Still, it is possible that a subdev has the v4l2_dev field initialized and is not added to the v4l2_device list of subdevs (v4l2_dev->subdevs). Then function v4l2_device_unregister_subdev() checks for valid sd->v4l2_dev and attempts to remove (not yet added) subdev from v4l2_dev->subdevs. This subdev (un)registration code seems buggy, unless I'm missing something... > Since in function v4l2_device_unregister_subdev() there is a check like > > 259 /* return if it isn't registered */ > 260 if (sd == NULL || sd->v4l2_dev == NULL) > 261 return; > > i.e. if subdev is not really registered, e.g. internal .registered > op fails, it should be NULL. > > In my case sd wasn't null since this structure was embedded in > other one. -- Regards, Sylwester -- To unsubscribe from this list: send the line "unsubscribe linux-media" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
