Hejssan! On Fri, Apr 28, 2017 at 01:47:48PM +0200, Niklas Söderlund wrote: > On 2017-04-28 13:28:17 +0300, Sakari Ailus wrote: > > Hi Niklas, > > > > Thank you for the patch. > > > > Do you happen to have a driver that would use this, to see some example of > > how the code is to be used? > > Yes, the latest R-Car CSI-2 series make use of this, see: > > https://www.spinics.net/lists/linux-renesas-soc/msg13693.html Ah, thanks. I'll take a look at that --- which should do for other reasons as well... ... > > > + > > > + /* > > > + * This function can be called recursively so the list > > > + * might be modified in a recursive call. Start from the > > > + * top of the list each iteration. > > > + */ > > > + found = 1; > > > + while (found) { > > > + found = 0; > > > > > > - list_for_each_entry_safe(sd, tmp, &subdev_list, async_list) { > > > - int ret; > > > + list_for_each_entry_safe(sd, tmp, &subdev_list, async_list) { > > > + int ret; > > > > > > - asd = v4l2_async_belongs(notifier, sd); > > > - if (!asd) > > > - continue; > > > + asd = v4l2_async_belongs(notifier, sd); > > > + if (!asd) > > > + continue; > > > > > > - ret = v4l2_async_test_notify(notifier, sd, asd); > > > - if (ret < 0) { > > > - mutex_unlock(&list_lock); > > > - return ret; > > > + ret = v4l2_async_test_notify(notifier, sd, asd); > > > + if (ret < 0) { > > > + if (!subnotifier) > > > + mutex_unlock(&list_lock); > > > + return ret; > > > + } > > > + > > > + found = 1; > > > + break; > > > } > > > } > > > > > > /* Keep also completed notifiers on the list */ > > > list_add(¬ifier->list, ¬ifier_list); > > > > > > - mutex_unlock(&list_lock); > > > + if (!subnotifier) > > > + mutex_unlock(&list_lock); > > > > > > return 0; > > > } > > > + > > > +int v4l2_async_subnotifier_register(struct v4l2_subdev *sd, > > > + struct v4l2_async_notifier *notifier) > > > +{ > > > + if (!sd->v4l2_dev) { > > > + dev_err(sd->dev ? sd->dev : NULL, sd->dev is enough. > > > + "Can't register subnotifier for without v4l2_dev\n"); > > > + return -EINVAL; > > > > When did this start happening? :-) > > What do you mean? I'm not sure I understand this comment. Uh, right. So the caller simply needs to specify v4l2_dev? The same applies to v4l2_async_notifier_register() which does not test that --- but it should. How about adding this change in a separate patch to what will be called v4l2_async_do_notifier_register()? > > > > > > + } > > > + > > > + return v4l2_async_do_notifier_register(sd->v4l2_dev, notifier, true); > > > +} > > > +EXPORT_SYMBOL(v4l2_async_subnotifier_register); > > > + > > > +int v4l2_async_notifier_register(struct v4l2_device *v4l2_dev, > > > + struct v4l2_async_notifier *notifier) > > > +{ > > > + return v4l2_async_do_notifier_register(v4l2_dev, notifier, false); > > > +} > > > EXPORT_SYMBOL(v4l2_async_notifier_register); > > > > > > -void v4l2_async_notifier_unregister(struct v4l2_async_notifier *notifier) > > > +static void > > > +v4l2_async_do_notifier_unregister(struct v4l2_async_notifier *notifier, > > > + bool subnotifier) > > > { > > > struct v4l2_subdev *sd, *tmp; > > > unsigned int notif_n_subdev = notifier->num_subdevs; > > > @@ -210,7 +248,8 @@ void v4l2_async_notifier_unregister(struct v4l2_async_notifier *notifier) > > > "Failed to allocate device cache!\n"); > > > } > > > > > > - mutex_lock(&list_lock); > > > + if (!subnotifier) > > > + mutex_lock(&list_lock); > > > > > > list_del(¬ifier->list); > > > > > > @@ -237,15 +276,20 @@ void v4l2_async_notifier_unregister(struct v4l2_async_notifier *notifier) > > > put_device(d); > > > } > > > > > > - mutex_unlock(&list_lock); > > > + if (!subnotifier) > > > + mutex_unlock(&list_lock); > > > > > > /* > > > * Call device_attach() to reprobe devices > > > * > > > * NOTE: If dev allocation fails, i is 0, and the whole loop won't be > > > * executed. > > > + * TODO: If we are unregistering a subdevice notifier we can't reprobe > > > + * since the lock_list is held by the master device and attaching that > > > + * device would call v4l2_async_register_subdev() and end in a deadlock > > > + * on list_lock. > > > */ > > > - while (i--) { > > > + while (i-- && !subnotifier) { > > > > Why is this not done for sub-notifiers? > > > > That said, the code here looks really dubious. But that's out of scope of > > the patchset. > > I try to explain this in the comment above :-) > > If this is called for sub-notifiers it will result in the probe function > of the subdevices it contained to be called. And as most drivers call > v4l2_async_register_subdev() in there probe functions this will result > in a dead lock since v4l2_async_register_subdev() will try to lock the > list_lock (which for sub-notifiers already is held). > > This is not optimal of course and I agree with you that this code is > dubious. It calls remove and then probe on all subdevices of the > notifier that is unregistered. Ack. Let's address this one later. -- Trevliga hälsningar, Sakari Ailus e-mail: sakari.ailus@xxxxxx XMPP: sailus@xxxxxxxxxxxxxx
