From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from lb3-smtp-cloud2.xs4all.net ([194.109.24.29]:38367 "EHLO lb3-smtp-cloud2.xs4all.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1750863AbdE2KZD (ORCPT ); Mon, 29 May 2017 06:25:03 -0400 Subject: Re: [PATCH v2 2/2] v4l: async: add subnotifier registration for subdevices To: =?UTF-8?Q?Niklas_S=c3=b6derlund?= , Mauro Carvalho Chehab , Sakari Ailus , linux-media@vger.kernel.org Cc: Kieran Bingham , linux-renesas-soc@vger.kernel.org, Laurent Pinchart , =?UTF-8?Q?Niklas_S=c3=b6derlund?= References: <20170524000727.12936-1-niklas.soderlund@ragnatech.se> <20170524000727.12936-3-niklas.soderlund@ragnatech.se> From: Hans Verkuil Message-ID: Date: Mon, 29 May 2017 12:24:58 +0200 MIME-Version: 1.0 In-Reply-To: <20170524000727.12936-3-niklas.soderlund@ragnatech.se> Content-Type: text/plain; charset=utf-8; format=flowed Content-Language: en-US Content-Transfer-Encoding: 8bit Sender: linux-renesas-soc-owner@vger.kernel.org List-ID: On 05/24/2017 02:07 AM, Niklas Söderlund wrote: > From: Niklas Söderlund > > When registered() of v4l2_subdev_internal_ops is called the subdevice When the registered() callback of... > have access to the master devices v4l2_dev and it's called with the have access -> has access (since it's just one subdevice) > async frameworks list_lock held. In this context the subdevice can > register its own notifiers to allow for incremental discovery of > subdevices. > > The master device registers the subdevices closest to itself in its > notifier while the subdevice(s) themself register notifiers for there themself -> themselves (or better, just drop it) there -> their > closest neighboring devices when they are registered. Using this > incremental approach two problems can be solved. solved. -> solved: > > 1. The master device no longer have to care how many devices exist in have -> has > the pipeline. It only needs to care about its closest subdevice and > arbitrary long pipelines can be created without having to adapt the > master device for each case. Nice! :-) > > 2. Subdevices which are represented as a single DT node but register > more then one subdevice can use this to further the pipeline then -> than 'further the...': would 'improve the...' be better? It's not entirely clear to me what you mean. > discovery. Since the subdevice driver is the only one who knows which discovery. Since -> discovery, since > of its subdevices is linked with which subdevice of a neighboring DT > node. > > To enable subdevices to register/unregister notifiers from the > registered()/unregistered() callback v4l2_async_subnotifier_register() > and v4l2_async_subnotifier_unregister() are added. These new notifier > register functions are similar to the master device equivalent functions > but run without taking the v4l2-async list_lock which already are held are -> is > when he registered()/unregistered() callbacks are called. he -> the > > Signed-off-by: Niklas Söderlund > --- > Documentation/media/kapi/v4l2-subdev.rst | 20 ++++++++ > drivers/media/v4l2-core/v4l2-async.c | 88 ++++++++++++++++++++++++++------ > include/media/v4l2-async.h | 22 ++++++++ > 3 files changed, 113 insertions(+), 17 deletions(-) > > diff --git a/Documentation/media/kapi/v4l2-subdev.rst b/Documentation/media/kapi/v4l2-subdev.rst > index e1f0b726e438f963..28ae681c63ff1330 100644 > --- a/Documentation/media/kapi/v4l2-subdev.rst > +++ b/Documentation/media/kapi/v4l2-subdev.rst > @@ -262,6 +262,26 @@ is called. After all subdevices have been located the .complete() callback is > called. When a subdevice is removed from the system the .unbind() method is > called. All three callbacks are optional. > > +Subdevice drivers might in turn register subnotifier objects with an > +array of other subdevice descriptors that the subdevice needs for its > +own operation. Subnotifiers are an extension of the bridge drivers > +notifier to allow for a incremental registering and matching of > +subdevices. This is useful when a driver only have information about have -> has > +which subdevice is closet it self and would require knowledge from the closet -> closest it self -> to itself > +driver of that subdevice to know which other subdevice(s) lies beyond. lies -> lie > +By registering subnotifiers drivers can incrementally move the subdevice > +matching down the chain of drivers. This is performed using the > +:c:func:`v4l2_async_subnotifier_register` call. To unregister the > +subnotifier the driver has to call > +:c:func:`v4l2_async_subnotifier_unregister`. These functions and its its -> their > +arguments behave almost the same as the bridge driver notifiers > +described above and are treated equally by the V4L2 core when matching > +asynchronously registered subdevices. The differences are that the > +subnotifier functions act on :c:type:`v4l2_subdev` instead of > +:c:type:`v4l2_device` and that they should be called from the subdevices subdevices -> subdevice's > +``.registered()`` and ``.unregistered()`` > +:c:type:`v4l2_subdev_internal_ops` callbacks instead of at probe time. > + > V4L2 sub-device userspace API > ----------------------------- > > diff --git a/drivers/media/v4l2-core/v4l2-async.c b/drivers/media/v4l2-core/v4l2-async.c > index c16200c88417b151..e1e181db90f789c0 100644 > --- a/drivers/media/v4l2-core/v4l2-async.c > +++ b/drivers/media/v4l2-core/v4l2-async.c > @@ -141,11 +141,13 @@ static void v4l2_async_cleanup(struct v4l2_subdev *sd) > sd->dev = NULL; > } > > -int v4l2_async_notifier_register(struct v4l2_device *v4l2_dev, > - struct v4l2_async_notifier *notifier) > +static int v4l2_async_do_notifier_register(struct v4l2_device *v4l2_dev, > + struct v4l2_async_notifier *notifier, > + bool subnotifier) > { > struct v4l2_subdev *sd, *tmp; > struct v4l2_async_subdev *asd; > + bool found; > int i; > > if (!v4l2_dev || !notifier->num_subdevs || > @@ -174,32 +176,65 @@ int v4l2_async_notifier_register(struct v4l2_device *v4l2_dev, > list_add_tail(&asd->list, ¬ifier->waiting); > } > > - mutex_lock(&list_lock); > + if (subnotifier) > + lockdep_assert_held(&list_lock); > + else > + mutex_lock(&list_lock); > + > + /* > + * 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 = true; > + while (found) { > + found = false; > > - 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 = true; > + 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) > +{ > + 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; > @@ -216,7 +251,10 @@ void v4l2_async_notifier_unregister(struct v4l2_async_notifier *notifier) > "Failed to allocate device cache!\n"); > } > > - mutex_lock(&list_lock); > + if (subnotifier) > + lockdep_assert_held(&list_lock); > + else > + mutex_lock(&list_lock); > > list_del(¬ifier->list); > > @@ -243,15 +281,20 @@ 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) { > struct device *d = dev[i]; > > if (d && device_attach(d) < 0) { > @@ -275,6 +318,17 @@ void v4l2_async_notifier_unregister(struct v4l2_async_notifier *notifier) > * upon notifier registration. > */ > } > + > +void v4l2_async_subnotifier_unregister(struct v4l2_async_notifier *notifier) > +{ > + v4l2_async_do_notifier_unregister(notifier, true); > +} > +EXPORT_SYMBOL(v4l2_async_subnotifier_unregister); > + > +void v4l2_async_notifier_unregister(struct v4l2_async_notifier *notifier) > +{ > + v4l2_async_do_notifier_unregister(notifier, false); > +} > EXPORT_SYMBOL(v4l2_async_notifier_unregister); > > int v4l2_async_register_subdev(struct v4l2_subdev *sd) > diff --git a/include/media/v4l2-async.h b/include/media/v4l2-async.h > index c69d8c8a66d0093a..7d55a5b0adc86580 100644 > --- a/include/media/v4l2-async.h > +++ b/include/media/v4l2-async.h > @@ -105,6 +105,18 @@ struct v4l2_async_notifier { > }; > > /** > + * v4l2_async_notifier_register - registers a subdevice asynchronous subnotifier > + * > + * @sd: pointer to &struct v4l2_subdev > + * @notifier: pointer to &struct v4l2_async_notifier > + * > + * This function assumes the async list_lock is already locked, allowing > + * it to be used from struct v4l2_subdev_internal_ops registered() callback. from -> from the > + */ > +int v4l2_async_subnotifier_register(struct v4l2_subdev *sd, > + struct v4l2_async_notifier *notifier); > + > +/** > * v4l2_async_notifier_register - registers a subdevice asynchronous notifier > * > * @v4l2_dev: pointer to &struct v4l2_device > @@ -114,6 +126,16 @@ int v4l2_async_notifier_register(struct v4l2_device *v4l2_dev, > struct v4l2_async_notifier *notifier); > > /** > + * v4l2_async_subnotifier_unregister - unregisters a asynchronous subnotifier > + * > + * @notifier: pointer to &struct v4l2_async_notifier > + * > + * This function assumes the async list_lock is already locked, allowing > + * it to be used from struct v4l2_subdev_internal_ops unregistered() callback. from -> from the > + */ > +void v4l2_async_subnotifier_unregister(struct v4l2_async_notifier *notifier); > + > +/** > * v4l2_async_notifier_unregister - unregisters a subdevice asynchronous notifier > * > * @notifier: pointer to &struct v4l2_async_notifier > Nice work! After fixing the typos you can add my: Acked-by: Hans Verkuil I'd like to have another Ack from Sakari or Laurent before merging this, though. Regards, Hans