Hi Hans,
Thanks for the review!
On Mon, Sep 11, 2017 at 10:57:16AM +0200, Hans Verkuil wrote:
> On 09/11/2017 09:59 AM, Sakari Ailus wrote:
> > Registering a notifier has required the knowledge of struct v4l2_device
> > for the reason that sub-devices generally are registered to the
> > v4l2_device (as well as the media device, also available through
> > v4l2_device).
> >
> > This information is not available for sub-device drivers at probe time.
> >
> > What this patch does is that it allows registering notifiers without
> > having v4l2_device around. Instead the sub-device pointer is stored in the
> > notifier. Once the sub-device of the driver that registered the notifier
> > is registered, the notifier will gain the knowledge of the v4l2_device,
> > and the binding of async sub-devices from the sub-device driver's notifier
> > may proceed.
> >
> > The root notifier's complete callback is only called when all sub-device
> > notifiers are completed.
> >
> > Signed-off-by: Sakari Ailus <sakari.ailus@xxxxxxxxxxxxxxx>
> > ---
> > drivers/media/v4l2-core/v4l2-async.c | 217 ++++++++++++++++++++++++++++++-----
> > include/media/v4l2-async.h | 16 ++-
> > 2 files changed, 202 insertions(+), 31 deletions(-)
> >
> > diff --git a/drivers/media/v4l2-core/v4l2-async.c b/drivers/media/v4l2-core/v4l2-async.c
> > index 9ebc2e079d03..6f788b2e922a 100644
> > --- a/drivers/media/v4l2-core/v4l2-async.c
> > +++ b/drivers/media/v4l2-core/v4l2-async.c
> > @@ -53,6 +53,10 @@ static int v4l2_async_notifier_call_complete(struct v4l2_async_notifier *n)
> > return n->ops->complete(n);
> > }
> >
> > +static int v4l2_async_match_notify(struct v4l2_async_notifier *notifier,
> > + struct v4l2_subdev *sd,
> > + struct v4l2_async_subdev *asd);
> > +
> > static bool match_i2c(struct v4l2_subdev *sd, struct v4l2_async_subdev *asd)
> > {
> > #if IS_ENABLED(CONFIG_I2C)
> > @@ -124,14 +128,128 @@ static struct v4l2_async_subdev *v4l2_async_find_match(
> > return NULL;
> > }
> >
> > +/* Get the sub-device notifier registered by a sub-device driver. */
> > +static struct v4l2_async_notifier *v4l2_async_get_subdev_notifier(
>
> I prefer to call this v4l2_async_find_subdev_notifier(). 'get' suggests
> a getter function, but this actually has to find it. I think this may have
> confused me during an earlier review of this code. The comment also needs
> updating: "Find the sub-device...".
Yes, makes sense. Get also suggests that there would be reference counting
which is not the case here.
I made the corresponding change to v4l2_async_notifier_find_v4l2_dev() as
well.
>
> > + struct v4l2_subdev *sd)
> > +{
> > + struct v4l2_async_notifier *n;
> > +
> > + list_for_each_entry(n, ¬ifier_list, list)
> > + if (n->sd == sd)
> > + return n;
> > +
> > + return NULL;
> > +}
> > +
> > +/* Return true if all sub-device notifiers are complete, false otherwise. */
> > +static bool v4l2_async_subdev_notifiers_complete(
> > + struct v4l2_async_notifier *notifier)
> > +{
> > + struct v4l2_subdev *sd;
> > +
> > + if (!list_empty(¬ifier->waiting))
> > + return false;
> > +
> > + list_for_each_entry(sd, ¬ifier->done, async_list) {
> > + struct v4l2_async_notifier *subdev_notifier =
> > + v4l2_async_get_subdev_notifier(sd);
>
> Would it make sense to add a 'struct v4l2_async_notifier *subdev_notifier'
> field to struct v4l2_subdev? It's set when a subdev registers a notifier.
>
> That way you can just use sd->subdev_notifier here.
>
> I wonder if v4l2_async_get_subdev_notifier() is needed at all if you do
> this.
I thought of that, but ended up keeping the information in the notifier. As
the information is already available elsewhere, I didn't end up adding a
new field for the purpose. This is certainly not performance critical
either.
>
> > +
> > + if (!subdev_notifier)
> > + continue;
> > +
> > + if (!v4l2_async_subdev_notifiers_complete(subdev_notifier))
> > + return false;
> > + }
> > +
> > + return true;
> > +}
> > +
> > +/* Get v4l2_device related to the notifier if one can be found. */
> > +static struct v4l2_device *v4l2_async_notifier_get_v4l2_dev(
> > + struct v4l2_async_notifier *notifier)
> > +{
> > + while (notifier->parent)
> > + notifier = notifier->parent;
> > +
> > + return notifier->v4l2_dev;
> > +}
> > +
> > +/* Test all async sub-devices in a notifier for a match. */
> > +static int v4l2_async_notifier_try_all_subdevs(
> > + struct v4l2_async_notifier *notifier)
> > +{
> > + struct v4l2_subdev *sd;
> > +
> > + if (!v4l2_async_notifier_get_v4l2_dev(notifier))
> > + return 0;
> > +
> > +again:
> > + list_for_each_entry(sd, &subdev_list, async_list) {
> > + struct v4l2_async_subdev *asd;
> > + int ret;
> > +
> > + asd = v4l2_async_find_match(notifier, sd);
> > + if (!asd)
> > + continue;
> > +
> > + ret = v4l2_async_match_notify(notifier, sd, asd);
> > + if (ret < 0)
> > + return ret;
> > +
> > + /*
> > + * v4l2_async_match_notify() may lead to registering a
> > + * new notifier and thus changing the async subdevs
> > + * list. In order to proceed safely from here, restart
> > + * parsing the list from the beginning.
> > + */
> > + goto again;
> > + }
> > +
> > + return 0;
> > +}
> > +
> > +/* Try completing a notifier. */
> > +static int v4l2_async_notifier_try_complete(
> > + struct v4l2_async_notifier *notifier)
> > +{
> > + do {
> > + int ret;
> > +
> > + /* Any local async sub-devices left? */
> > + if (!list_empty(¬ifier->waiting))
> > + return 0;
> > +
> > + /*
> > + * Any sub-device notifiers waiting for async subdevs
> > + * to be bound?
> > + */
> > + if (!v4l2_async_subdev_notifiers_complete(notifier))
> > + return 0;
> > +
> > + /* Proceed completing the notifier */
> > + ret = v4l2_async_notifier_call_complete(notifier);
> > + if (ret < 0)
> > + return ret;
> > +
> > + /*
> > + * Obtain notifier's parent. If there is one, repeat
> > + * the process, otherwise we're done here.
> > + */
> > + } while ((notifier = notifier->parent));
> > +
> > + return 0;
> > +}
> > +
> > static int v4l2_async_match_notify(struct v4l2_async_notifier *notifier,
> > struct v4l2_subdev *sd,
> > struct v4l2_async_subdev *asd)
> > {
> > + struct v4l2_async_notifier *subdev_notifier;
> > int ret;
> >
> > - ret = v4l2_device_register_subdev(notifier->v4l2_dev, sd);
> > - if (ret < 0)
> > + ret = v4l2_device_register_subdev(
> > + v4l2_async_notifier_get_v4l2_dev(notifier), sd);
> > + if (ret)
> > return ret;
> >
> > ret = v4l2_async_notifier_call_bound(notifier, sd, asd);
> > @@ -148,10 +266,20 @@ static int v4l2_async_match_notify(struct v4l2_async_notifier *notifier,
> > /* Move from the global subdevice list to notifier's done */
> > list_move(&sd->async_list, ¬ifier->done);
> >
> > - if (list_empty(¬ifier->waiting))
> > - return v4l2_async_notifier_call_complete(notifier);
> > + /*
> > + * See if the sub-device has a notifier. If it does, proceed
> > + * with checking for its async sub-devices.
> > + */
> > + subdev_notifier = v4l2_async_get_subdev_notifier(sd);
> > + if (subdev_notifier && !subdev_notifier->parent) {
> > + subdev_notifier->parent = notifier;
> > + ret = v4l2_async_notifier_try_all_subdevs(subdev_notifier);
> > + if (ret)
> > + return ret;
> > + }
> >
> > - return 0;
> > + /* Try completing the notifier and its parent(s). */
> > + return v4l2_async_notifier_try_complete(notifier);
> > }
> >
> > static void v4l2_async_cleanup(struct v4l2_subdev *sd)
> > @@ -163,20 +291,18 @@ 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_notifier_register(struct v4l2_async_notifier *notifier)
> > {
> > - struct v4l2_subdev *sd, *tmp;
> > struct v4l2_async_subdev *asd;
> > + int ret;
> > int i;
> >
> > - if (!v4l2_dev || notifier->num_subdevs > V4L2_MAX_SUBDEVS)
> > + if (notifier->num_subdevs > V4L2_MAX_SUBDEVS)
> > return -EINVAL;
> >
> > if (!notifier->num_subdevs)
> > return v4l2_async_notifier_call_complete(notifier);
> >
> > - notifier->v4l2_dev = v4l2_dev;
> > INIT_LIST_HEAD(¬ifier->waiting);
> > INIT_LIST_HEAD(¬ifier->done);
> >
> > @@ -200,18 +326,10 @@ int v4l2_async_notifier_register(struct v4l2_device *v4l2_dev,
> >
> > mutex_lock(&list_lock);
> >
> > - list_for_each_entry_safe(sd, tmp, &subdev_list, async_list) {
> > - int ret;
> > -
> > - asd = v4l2_async_find_match(notifier, sd);
> > - if (!asd)
> > - continue;
> > -
> > - ret = v4l2_async_match_notify(notifier, sd, asd);
> > - if (ret < 0) {
> > - mutex_unlock(&list_lock);
> > - return ret;
> > - }
> > + ret = v4l2_async_notifier_try_all_subdevs(notifier);
> > + if (ret) {
> > + mutex_unlock(&list_lock);
> > + return ret;
> > }
> >
> > /* Keep also completed notifiers on the list */
> > @@ -221,28 +339,67 @@ int v4l2_async_notifier_register(struct v4l2_device *v4l2_dev,
> >
> > return 0;
> > }
> > +
> > +int v4l2_async_notifier_register(struct v4l2_device *v4l2_dev,
> > + struct v4l2_async_notifier *notifier)
> > +{
> > + if (!v4l2_dev || notifier->sd)
>
> Should this be a WARN_ON?
Added WARN_ON().
>
> > + return -EINVAL;
> > +
> > + notifier->v4l2_dev = v4l2_dev;
> > +
> > + return __v4l2_async_notifier_register(notifier);
> > +}
> > EXPORT_SYMBOL(v4l2_async_notifier_register);
> >
> > -void v4l2_async_notifier_unregister(struct v4l2_async_notifier *notifier)
> > +int v4l2_async_subdev_notifier_register(struct v4l2_subdev *sd,
> > + struct v4l2_async_notifier *notifier)
> > {
> > - struct v4l2_subdev *sd, *tmp;
> > + if (!sd || notifier->v4l2_dev)
>
> Ditto.
Indeed.
>
> > + return -EINVAL;
> >
> > - if (!notifier->v4l2_dev)
> > - return;
> > + notifier->sd = sd;
> >
> > - mutex_lock(&list_lock);
> > + return __v4l2_async_notifier_register(notifier);
> > +}
> > +EXPORT_SYMBOL(v4l2_async_subdev_notifier_register);
> >
> > - list_del(¬ifier->list);
> > +/* Unbind all sub-devices in the notifier tree. */
> > +static void v4l2_async_notifier_unbind_all_subdevs(
> > + struct v4l2_async_notifier *notifier)
> > +{
> > + struct v4l2_subdev *sd, *tmp;
> >
> > list_for_each_entry_safe(sd, tmp, ¬ifier->done, async_list) {
> > + struct v4l2_async_notifier *subdev_notifier =
> > + v4l2_async_get_subdev_notifier(sd);
> > +
> > + if (subdev_notifier)
> > + v4l2_async_notifier_unbind_all_subdevs(subdev_notifier);
> > +
> > v4l2_async_cleanup(sd);
> >
> > v4l2_async_notifier_call_unbind(notifier, sd, sd->asd);
> > +
> > + list_del(&sd->async_list);
> > + list_add(&sd->async_list, &subdev_list);
> > }
> >
> > - mutex_unlock(&list_lock);
> > + notifier->parent = NULL;
>
> Shouldn't notifier->v4l2_dev and notifier->sd be set to NULL as well?
> I can't really tell.
Well spotted. Yes. This was actually broken by the patch; v4l2_dev used to
be set NULL. Will fix.
>
> > +}
> > +
> > +void v4l2_async_notifier_unregister(struct v4l2_async_notifier *notifier)
> > +{
> > + if (!notifier->v4l2_dev && !notifier->sd)
> > + return;
> >
> > - notifier->v4l2_dev = NULL;
> > + mutex_lock(&list_lock);
> > +
> > + v4l2_async_notifier_unbind_all_subdevs(notifier);
> > +
> > + list_del(¬ifier->list);
> > +
> > + mutex_unlock(&list_lock);
> > }
> > EXPORT_SYMBOL(v4l2_async_notifier_unregister);
> >
> > diff --git a/include/media/v4l2-async.h b/include/media/v4l2-async.h
> > index 3bc8a7c0d83f..cf409d45208c 100644
> > --- a/include/media/v4l2-async.h
> > +++ b/include/media/v4l2-async.h
> > @@ -102,7 +102,9 @@ struct v4l2_async_notifier_operations {
> > * @num_subdevs: number of subdevices used in the subdevs array
> > * @max_subdevs: number of subdevices allocated in the subdevs array
> > * @subdevs: array of pointers to subdevice descriptors
> > - * @v4l2_dev: pointer to struct v4l2_device
> > + * @v4l2_dev: v4l2_device of the root notifier, NULL otherwise
> > + * @sd: sub-device that registered the notifier, NULL otherwise
> > + * @parent: parent notifier carrying @v4l2_dev
>
> That's not correct, it only carries v4l2_dev if it is the root notifier.
> I think just 'parent notifier' is sufficient here.
Will change.
>
> > * @waiting: list of struct v4l2_async_subdev, waiting for their drivers
> > * @done: list of struct v4l2_subdev, already probed
> > * @list: member in a global list of notifiers
> > @@ -113,6 +115,8 @@ struct v4l2_async_notifier {
> > unsigned int max_subdevs;
> > struct v4l2_async_subdev **subdevs;
> > struct v4l2_device *v4l2_dev;
> > + struct v4l2_subdev *sd;
> > + struct v4l2_async_notifier *parent;
> > struct list_head waiting;
> > struct list_head done;
> > struct list_head list;
> > @@ -128,6 +132,16 @@ int v4l2_async_notifier_register(struct v4l2_device *v4l2_dev,
> > struct v4l2_async_notifier *notifier);
> >
> > /**
> > + * v4l2_async_subdev_notifier_register - registers a subdevice asynchronous
> > + * notifier for a sub-device
> > + *
> > + * @sd: pointer to &struct v4l2_subdev
> > + * @notifier: pointer to &struct v4l2_async_notifier
> > + */
> > +int v4l2_async_subdev_notifier_register(struct v4l2_subdev *sd,
> > + struct v4l2_async_notifier *notifier);
> > +
> > +/**
> > * v4l2_async_notifier_unregister - unregisters a subdevice asynchronous notifier
> > *
> > * @notifier: pointer to &struct v4l2_async_notifier
> >
--
Regards,
Sakari Ailus
e-mail: sakari.ailus@xxxxxx
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