[PATCH v16 18/32] v4l: async: Allow binding notifiers to sub-devices

Sakari Ailus
2017-10-26T07:54:38Z

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 complete callback of the root notifier will be called only when the
v4l2_device is available and no notifier has pending sub-devices to bind.
No complete callbacks are supported for sub-device notifiers.

Signed-off-by: Sakari Ailus <sakari.ailus@linux.intel.com>
Acked-by: Hans Verkuil <hans.verkuil@cisco.com>
---
drivers/media/v4l2-core/v4l2-async.c | 216 ++++++++++++++++++++++++++++-------
include/media/v4l2-async.h | 19 ++-
2 files changed, 190 insertions(+), 45 deletions(-)

diff --git a/drivers/media/v4l2-core/v4l2-async.c b/drivers/media/v4l2-core/v4l2-async.c
index eb31d96254d1..ed539c4fd5dc 100644
--- a/drivers/media/v4l2-core/v4l2-async.c
+++ b/drivers/media/v4l2-core/v4l2-async.c
@@ -124,11 +124,87 @@ static struct v4l2_async_subdev *v4l2_async_find_match(
return NULL;
}

+/* Find the sub-device notifier registered by a sub-device driver. */
+static struct v4l2_async_notifier *v4l2_async_find_subdev_notifier(
+ struct v4l2_subdev *sd)
+{
+ struct v4l2_async_notifier *n;
+
+ list_for_each_entry(n, &notifier_list, list)
+ if (n->sd == sd)
+ return n;
+
+ return NULL;
+}
+
+/* Get v4l2_device related to the notifier if one can be found. */
+static struct v4l2_device *v4l2_async_notifier_find_v4l2_dev(
+ struct v4l2_async_notifier *notifier)
+{
+ while (notifier->parent)
+ notifier = notifier->parent;
+
+ return notifier->v4l2_dev;
+}
+
+/*
+ * Return true if all child sub-device notifiers are complete, false otherwise.
+ */
+static bool v4l2_async_notifier_can_complete(
+ struct v4l2_async_notifier *notifier)
+{
+ struct v4l2_subdev *sd;
+
+ if (!list_empty(&notifier->waiting))
+ return false;
+
+ list_for_each_entry(sd, &notifier->done, async_list) {
+ struct v4l2_async_notifier *subdev_notifier =
+ v4l2_async_find_subdev_notifier(sd);
+
+ if (subdev_notifier &&
+ !v4l2_async_notifier_can_complete(subdev_notifier))
+ return false;
+ }
+
+ return true;
+}
+
+/*
+ * Complete the master notifier if possible. This is done when all async
+ * sub-devices have been bound; v4l2_device is also available then.
+ */
+static int v4l2_async_notifier_try_complete(
+ struct v4l2_async_notifier *notifier)
+{
+ /* Quick check whether there are still more sub-devices here. */
+ if (!list_empty(&notifier->waiting))
+ return 0;
+
+ /* Check the entire notifier tree; find the root notifier first. */
+ while (notifier->parent)
+ notifier = notifier->parent;
+
+ /* This is root if it has v4l2_dev. */
+ if (!notifier->v4l2_dev)
+ return 0;
+
+ /* Is everything ready? */
+ if (!v4l2_async_notifier_can_complete(notifier))
+ return 0;
+
+ return v4l2_async_notifier_call_complete(notifier);
+}
+
+static int v4l2_async_notifier_try_all_subdevs(
+ struct v4l2_async_notifier *notifier);
+
static int v4l2_async_match_notify(struct v4l2_async_notifier *notifier,
struct v4l2_device *v4l2_dev,
struct v4l2_subdev *sd,
struct v4l2_async_subdev *asd)
{
+ struct v4l2_async_notifier *subdev_notifier;
int ret;

ret = v4l2_device_register_subdev(v4l2_dev, sd);
@@ -149,17 +225,36 @@ 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, &notifier->done);

- return 0;
+ /*
+ * See if the sub-device has a notifier. If not, return here.
+ */
+ subdev_notifier = v4l2_async_find_subdev_notifier(sd);
+ if (!subdev_notifier || subdev_notifier->parent)
+ return 0;
+
+ /*
+ * Proceed with checking for the sub-device notifier's async
+ * sub-devices, and return the result. The error will be handled by the
+ * caller.
+ */
+ subdev_notifier->parent = notifier;
+
+ return v4l2_async_notifier_try_all_subdevs(subdev_notifier);
}

/* 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_device *v4l2_dev = notifier->v4l2_dev;
- struct v4l2_subdev *sd, *tmp;
+ struct v4l2_device *v4l2_dev =
+ v4l2_async_notifier_find_v4l2_dev(notifier);
+ struct v4l2_subdev *sd;

- list_for_each_entry_safe(sd, tmp, &subdev_list, async_list) {
+ if (!v4l2_dev)
+ return 0;
+
+again:
+ list_for_each_entry(sd, &subdev_list, async_list) {
struct v4l2_async_subdev *asd;
int ret;

@@ -168,10 +263,16 @@ static int v4l2_async_notifier_try_all_subdevs(
continue;

ret = v4l2_async_match_notify(notifier, v4l2_dev, sd, asd);
- if (ret < 0) {
- mutex_unlock(&list_lock);
+ 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;
@@ -185,17 +286,26 @@ static void v4l2_async_cleanup(struct v4l2_subdev *sd)
sd->asd = NULL;
}

+/* 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, &notifier->done, async_list) {
+ struct v4l2_async_notifier *subdev_notifier =
+ v4l2_async_find_subdev_notifier(sd);
+
+ if (subdev_notifier)
+ v4l2_async_notifier_unbind_all_subdevs(subdev_notifier);
+
v4l2_async_notifier_call_unbind(notifier, sd, sd->asd);
v4l2_async_cleanup(sd);

list_move(&sd->async_list, &subdev_list);
}
+
+ notifier->parent = NULL;
}

static int __v4l2_async_notifier_register(struct v4l2_async_notifier *notifier)
@@ -210,15 +320,6 @@ static int __v4l2_async_notifier_register(struct v4l2_async_notifier *notifier)
INIT_LIST_HEAD(&notifier->waiting);
INIT_LIST_HEAD(&notifier->done);

- if (!notifier->num_subdevs) {
- int ret;
-
- ret = v4l2_async_notifier_call_complete(notifier);
- notifier->v4l2_dev = NULL;
-
- return ret;
- }
-
for (i = 0; i < notifier->num_subdevs; i++) {
asd = notifier->subdevs[i];

@@ -240,16 +341,12 @@ static int __v4l2_async_notifier_register(struct v4l2_async_notifier *notifier)
mutex_lock(&list_lock);

ret = v4l2_async_notifier_try_all_subdevs(notifier);
- if (ret) {
- mutex_unlock(&list_lock);
- return ret;
- }
+ if (ret)
+ goto err_unbind;

- if (list_empty(&notifier->waiting)) {
- ret = v4l2_async_notifier_call_complete(notifier);
- if (ret)
- goto err_complete;
- }
+ ret = v4l2_async_notifier_try_complete(notifier);
+ if (ret)
+ goto err_unbind;

/* Keep also completed notifiers on the list */
list_add(&notifier->list, &notifier_list);
@@ -258,7 +355,10 @@ static int __v4l2_async_notifier_register(struct v4l2_async_notifier *notifier)

return 0;

-err_complete:
+err_unbind:
+ /*
+ * On failure, unbind all sub-devices registered through this notifier.
+ */
v4l2_async_notifier_unbind_all_subdevs(notifier);

mutex_unlock(&list_lock);
@@ -271,7 +371,7 @@ int v4l2_async_notifier_register(struct v4l2_device *v4l2_dev,
{
int ret;

- if (WARN_ON(!v4l2_dev))
+ if (WARN_ON(!v4l2_dev || notifier->sd))
return -EINVAL;

notifier->v4l2_dev = v4l2_dev;
@@ -284,20 +384,39 @@ int v4l2_async_notifier_register(struct v4l2_device *v4l2_dev,
}
EXPORT_SYMBOL(v4l2_async_notifier_register);

+int v4l2_async_subdev_notifier_register(struct v4l2_subdev *sd,
+ struct v4l2_async_notifier *notifier)
+{
+ int ret;
+
+ if (WARN_ON(!sd || notifier->v4l2_dev))
+ return -EINVAL;
+
+ notifier->sd = sd;
+
+ ret = __v4l2_async_notifier_register(notifier);
+ if (ret)
+ notifier->sd = NULL;
+
+ return ret;
+}
+EXPORT_SYMBOL(v4l2_async_subdev_notifier_register);
+
void v4l2_async_notifier_unregister(struct v4l2_async_notifier *notifier)
{
- if (!notifier->v4l2_dev)
+ if (!notifier->v4l2_dev && !notifier->sd)
return;

mutex_lock(&list_lock);

- list_del(&notifier->list);
-
v4l2_async_notifier_unbind_all_subdevs(notifier);

- mutex_unlock(&list_lock);
-
+ notifier->sd = NULL;
notifier->v4l2_dev = NULL;
+
+ list_del(&notifier->list);
+
+ mutex_unlock(&list_lock);
}
EXPORT_SYMBOL(v4l2_async_notifier_unregister);

@@ -333,6 +452,7 @@ EXPORT_SYMBOL_GPL(v4l2_async_notifier_cleanup);

int v4l2_async_register_subdev(struct v4l2_subdev *sd)
{
+ struct v4l2_async_notifier *subdev_notifier;
struct v4l2_async_notifier *notifier;
int ret;

@@ -349,24 +469,26 @@ int v4l2_async_register_subdev(struct v4l2_subdev *sd)
INIT_LIST_HEAD(&sd->async_list);

list_for_each_entry(notifier, &notifier_list, list) {
- struct v4l2_async_subdev *asd = v4l2_async_find_match(notifier,
- sd);
+ struct v4l2_device *v4l2_dev =
+ v4l2_async_notifier_find_v4l2_dev(notifier);
+ struct v4l2_async_subdev *asd;
int ret;

+ if (!v4l2_dev)
+ continue;
+
+ asd = v4l2_async_find_match(notifier, sd);
if (!asd)
continue;

ret = v4l2_async_match_notify(notifier, notifier->v4l2_dev, sd,
asd);
if (ret)
- goto err_unlock;
-
- if (!list_empty(&notifier->waiting))
- goto out_unlock;
+ goto err_unbind;

- ret = v4l2_async_notifier_call_complete(notifier);
+ ret = v4l2_async_notifier_try_complete(notifier);
if (ret)
- goto err_cleanup;
+ goto err_unbind;

goto out_unlock;
}
@@ -379,11 +501,19 @@ int v4l2_async_register_subdev(struct v4l2_subdev *sd)

return 0;

-err_cleanup:
- v4l2_async_notifier_call_unbind(notifier, sd, sd->asd);
+err_unbind:
+ /*
+ * Complete failed. Unbind the sub-devices bound through registering
+ * this async sub-device.
+ */
+ subdev_notifier = v4l2_async_find_subdev_notifier(sd);
+ if (subdev_notifier)
+ v4l2_async_notifier_unbind_all_subdevs(subdev_notifier);
+
+ if (sd->asd)
+ v4l2_async_notifier_call_unbind(notifier, sd, sd->asd);
v4l2_async_cleanup(sd);

-err_unlock:
mutex_unlock(&list_lock);

return ret;
diff --git a/include/media/v4l2-async.h b/include/media/v4l2-async.h
index 68606afb5ef9..17c4ac7c73e8 100644
--- a/include/media/v4l2-async.h
+++ b/include/media/v4l2-async.h
@@ -82,7 +82,8 @@ struct v4l2_async_subdev {
/**
* struct v4l2_async_notifier_operations - Asynchronous V4L2 notifier operations
* @bound: a subdevice driver has successfully probed one of the subdevices
- * @complete: all subdevices have been probed successfully
+ * @complete: All subdevices have been probed successfully. The complete
+ * callback is only executed for the root notifier.
* @unbind: a subdevice is leaving
*/
struct v4l2_async_notifier_operations {
@@ -102,7 +103,9 @@ 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
* @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 +116,8 @@ 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 +133,16 @@ 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
--
2.11.0