Re: [PATCH v3 03/13] media: v4l2: async: Add v4l2_async_notifier_add_subdev

Steve Longerbeam <slongerbeam@xxxxxxxxx> · Fri, 20 Apr 2018 10:12:33 -0700

Hi Sakari,


On 04/20/2018 05:24 AM, Sakari Ailus wrote:
Hi Steve,

Thanks for the patchset.

On Tue, Mar 20, 2018 at 05:37:19PM -0700, Steve Longerbeam wrote:
v4l2_async_notifier_add_subdev() adds an asd to the notifier. It checks
that the asd's match_type is valid and that no other equivalent asd's
have already been added to this notifier's asd list, or to other
registered notifier's waiting or done lists, and increments num_subdevs.

v4l2_async_notifier_add_subdev() does not make use of the notifier subdevs
array, otherwise it would have to re-allocate the array every time the
function was called. In place of the subdevs array, the function adds
the asd to a new master asd_list. The function will return error with a
WARN() if it is ever called with the subdevs array allocated.

In v4l2_async_notifier_has_async_subdev(), __v4l2_async_notifier_register(),
and v4l2_async_notifier_cleanup(), alternatively operate on the subdevs
array or a non-empty notifier->asd_list.
I do agree with the approach, but this patch leaves the remaining users of
the subdevs array in the notifier intact. Could you rework them to use the
v4l2_async_notifier_add_subdev() as well?

There seem to be just a few of them --- exynos4-is and rcar_drif.

I count more than a few :)

% cd drivers/media && grep -l -r --include "*.[ch]" 
'notifier[\.\-]>*subdevs[   ]*='
v4l2-core/v4l2-async.c
platform/pxa_camera.c
platform/ti-vpe/cal.c
platform/exynos4-is/media-dev.c
platform/qcom/camss-8x16/camss.c
platform/soc_camera/soc_camera.c
platform/atmel/atmel-isi.c
platform/atmel/atmel-isc.c
platform/stm32/stm32-dcmi.c
platform/davinci/vpif_capture.c
platform/davinci/vpif_display.c
platform/renesas-ceu.c
platform/am437x/am437x-vpfe.c
platform/xilinx/xilinx-vipp.c
platform/rcar_drif.c


So not including v4l2-core, the list is:

pxa_camera
ti-vpe
exynos4-is
qcom
soc_camera
atmel
stm32
davinci
renesas-ceu
am437x
xilinx
rcar_drif


Given such a large list of the users of the notifier->subdevs array,
I think this should be done is two steps: submit this patchset first,
that keeps the backward compatibility, and then a subsequent patchset
that converts all drivers to use v4l2_async_notifier_add_subdev(), at
which point the subdevs array can be removed from struct 
v4l2_async_notifier.

Or, do you still think this should be done all at once? I could add a
large patch to this patchset that does the conversion and removes
the subdevs array.

Steve



Signed-off-by: Steve Longerbeam <steve_longerbeam@xxxxxxxxxx>
---
Changes since v2:
- add a NULL asd pointer check to v4l2_async_notifier_asd_valid().
Changes since v1:
- none
---
  drivers/media/v4l2-core/v4l2-async.c | 206 +++++++++++++++++++++++++++--------
  include/media/v4l2-async.h           |  22 ++++
  2 files changed, 184 insertions(+), 44 deletions(-)

diff --git a/drivers/media/v4l2-core/v4l2-async.c b/drivers/media/v4l2-core/v4l2-async.c
index b59bbac..7b7f7e2 100644
--- a/drivers/media/v4l2-core/v4l2-async.c
+++ b/drivers/media/v4l2-core/v4l2-async.c
@@ -366,16 +366,26 @@ static bool v4l2_async_notifier_has_async_subdev(
  	struct v4l2_async_notifier *notifier, struct v4l2_async_subdev *asd,
  	unsigned int this_index)
  {
+	struct v4l2_async_subdev *asd_y;
  	unsigned int j;
  
  	lockdep_assert_held(&list_lock);
  
  	/* Check that an asd is not being added more than once. */
-	for (j = 0; j < this_index; j++) {
-		struct v4l2_async_subdev *asd_y = notifier->subdevs[j];
-
-		if (asd_equal(asd, asd_y))
-			return true;
+	if (notifier->subdevs) {
+		for (j = 0; j < this_index; j++) {
+			asd_y = notifier->subdevs[j];
+			if (asd_equal(asd, asd_y))
+				return true;
+		}
+	} else {
+		j = 0;
+		list_for_each_entry(asd_y, &notifier->asd_list, asd_list) {
+			if (j++ >= this_index)
+				break;
+			if (asd_equal(asd, asd_y))
+				return true;
+		}
  	}
  
  	/* Check that an asd does not exist in other notifiers. */
@@ -386,10 +396,46 @@ static bool v4l2_async_notifier_has_async_subdev(
  	return false;
  }
  
-static int __v4l2_async_notifier_register(struct v4l2_async_notifier *notifier)
+static int v4l2_async_notifier_asd_valid(struct v4l2_async_notifier *notifier,
+					 struct v4l2_async_subdev *asd,
+					 unsigned int this_index)
  {
  	struct device *dev =
  		notifier->v4l2_dev ? notifier->v4l2_dev->dev : NULL;
+
+	if (!asd)
+		return -EINVAL;
+
+	switch (asd->match_type) {
+	case V4L2_ASYNC_MATCH_CUSTOM:
+	case V4L2_ASYNC_MATCH_DEVNAME:
+	case V4L2_ASYNC_MATCH_I2C:
+	case V4L2_ASYNC_MATCH_FWNODE:
+		if (v4l2_async_notifier_has_async_subdev(notifier, asd,
+							 this_index))
+			return -EEXIST;
+		break;
+	default:
+		dev_err(dev, "Invalid match type %u on %p\n",
+			asd->match_type, asd);
+		return -EINVAL;
+	}
+
+	return 0;
+}
+
+static void __v4l2_async_notifier_init(struct v4l2_async_notifier *notifier)
+{
+	lockdep_assert_held(&list_lock);
+
+	INIT_LIST_HEAD(&notifier->asd_list);
+	INIT_LIST_HEAD(&notifier->waiting);
+	INIT_LIST_HEAD(&notifier->done);
+	notifier->lists_initialized = true;
+}
+
+static int __v4l2_async_notifier_register(struct v4l2_async_notifier *notifier)
+{
  	struct v4l2_async_subdev *asd;
  	int ret;
  	int i;
@@ -397,34 +443,40 @@ static int __v4l2_async_notifier_register(struct v4l2_async_notifier *notifier)
  	if (notifier->num_subdevs > V4L2_MAX_SUBDEVS)
  		return -EINVAL;
  
-	INIT_LIST_HEAD(&notifier->waiting);
-	INIT_LIST_HEAD(&notifier->done);
-
  	mutex_lock(&list_lock);
  
-	for (i = 0; i < notifier->num_subdevs; i++) {
-		asd = notifier->subdevs[i];
+	if (!notifier->lists_initialized)
+		__v4l2_async_notifier_init(notifier);
  
-		switch (asd->match_type) {
-		case V4L2_ASYNC_MATCH_CUSTOM:
-		case V4L2_ASYNC_MATCH_DEVNAME:
-		case V4L2_ASYNC_MATCH_I2C:
-		case V4L2_ASYNC_MATCH_FWNODE:
-			if (v4l2_async_notifier_has_async_subdev(
-				    notifier, asd, i)) {
-				dev_err(dev,
-					"asd has already been registered or in notifier's subdev list\n");
-				ret = -EEXIST;
-				goto err_unlock;
-			}
-			break;
-		default:
-			dev_err(dev, "Invalid match type %u on %p\n",
-				asd->match_type, asd);
+	if (!list_empty(&notifier->asd_list)) {
+		/*
+		 * Caller must have either used v4l2_async_notifier_add_subdev
+		 * to add asd's to notifier->asd_list, or provided the
+		 * notifier->subdevs array, but not both.
+		 */
+		if (WARN_ON(notifier->subdevs)) {
  			ret = -EINVAL;
  			goto err_unlock;
  		}
-		list_add_tail(&asd->list, &notifier->waiting);
+
+		i = 0;
+		list_for_each_entry(asd, &notifier->asd_list, asd_list) {
+			ret = v4l2_async_notifier_asd_valid(notifier, asd, i++);
+			if (ret)
+				goto err_unlock;
+
+			list_add_tail(&asd->list, &notifier->waiting);
+		}
+	} else if (notifier->subdevs) {
+		for (i = 0; i < notifier->num_subdevs; i++) {
+			asd = notifier->subdevs[i];
+
+			ret = v4l2_async_notifier_asd_valid(notifier, asd, i);
+			if (ret)
+				goto err_unlock;
+
+			list_add_tail(&asd->list, &notifier->waiting);
+		}
  	}
  
  	ret = v4l2_async_notifier_try_all_subdevs(notifier);
@@ -514,36 +566,102 @@ void v4l2_async_notifier_unregister(struct v4l2_async_notifier *notifier)
  }
  EXPORT_SYMBOL(v4l2_async_notifier_unregister);
  
-void v4l2_async_notifier_cleanup(struct v4l2_async_notifier *notifier)
+static void __v4l2_async_notifier_cleanup(struct v4l2_async_notifier *notifier)
  {
+	struct v4l2_async_subdev *asd, *tmp;
  	unsigned int i;
  
-	if (!notifier || !notifier->max_subdevs)
+	if (!notifier)
  		return;
  
-	for (i = 0; i < notifier->num_subdevs; i++) {
-		struct v4l2_async_subdev *asd = notifier->subdevs[i];
+	if (notifier->subdevs) {
+		if (!notifier->max_subdevs)
+			return;
  
-		switch (asd->match_type) {
-		case V4L2_ASYNC_MATCH_FWNODE:
-			fwnode_handle_put(asd->match.fwnode);
-			break;
-		default:
-			WARN_ON_ONCE(true);
-			break;
+		for (i = 0; i < notifier->num_subdevs; i++) {
+			asd = notifier->subdevs[i];
+
+			switch (asd->match_type) {
+			case V4L2_ASYNC_MATCH_FWNODE:
+				fwnode_handle_put(asd->match.fwnode);
+				break;
+			default:
+				break;
+			}
+
+			kfree(asd);
  		}
  
-		kfree(asd);
+		notifier->max_subdevs = 0;
+		kvfree(notifier->subdevs);
+		notifier->subdevs = NULL;
+	} else if (notifier->lists_initialized) {
+		list_for_each_entry_safe(asd, tmp,
+					 &notifier->asd_list, asd_list) {
+			switch (asd->match_type) {
+			case V4L2_ASYNC_MATCH_FWNODE:
+				fwnode_handle_put(asd->match.fwnode);
+				break;
+			default:
+				break;
+			}
+
+			list_del(&asd->asd_list);
+			kfree(asd);
+		}
  	}
  
-	notifier->max_subdevs = 0;
  	notifier->num_subdevs = 0;
+}
  
-	kvfree(notifier->subdevs);
-	notifier->subdevs = NULL;
+void v4l2_async_notifier_cleanup(struct v4l2_async_notifier *notifier)
+{
+	mutex_lock(&list_lock);
+
+	__v4l2_async_notifier_cleanup(notifier);
+
+	mutex_unlock(&list_lock);
  }
  EXPORT_SYMBOL_GPL(v4l2_async_notifier_cleanup);
  
+int v4l2_async_notifier_add_subdev(struct v4l2_async_notifier *notifier,
+				   struct v4l2_async_subdev *asd)
+{
+	int ret = 0;
+
+	mutex_lock(&list_lock);
+
+	if (notifier->num_subdevs >= V4L2_MAX_SUBDEVS) {
+		ret = -EINVAL;
+		goto unlock;
+	}
+
+	if (!notifier->lists_initialized)
+		__v4l2_async_notifier_init(notifier);
+
+	/*
+	 * If caller uses this function, it cannot also allocate and
+	 * place asd's in the notifier->subdevs array.
+	 */
+	if (WARN_ON(notifier->subdevs)) {
+		ret = -EINVAL;
+		goto unlock;
+	}
+
+	ret = v4l2_async_notifier_asd_valid(notifier, asd,
+					    notifier->num_subdevs);
+	if (ret)
+		goto unlock;
+
+	list_add_tail(&asd->asd_list, &notifier->asd_list);
+	notifier->num_subdevs++;
+
+unlock:
+	mutex_unlock(&list_lock);
+	return ret;
+}
+EXPORT_SYMBOL_GPL(v4l2_async_notifier_add_subdev);
+
  int v4l2_async_register_subdev(struct v4l2_subdev *sd)
  {
  	struct v4l2_async_notifier *subdev_notifier;
@@ -617,7 +735,7 @@ void v4l2_async_unregister_subdev(struct v4l2_subdev *sd)
  	mutex_lock(&list_lock);
  
  	__v4l2_async_notifier_unregister(sd->subdev_notifier);
-	v4l2_async_notifier_cleanup(sd->subdev_notifier);
+	__v4l2_async_notifier_cleanup(sd->subdev_notifier);
  	kfree(sd->subdev_notifier);
  	sd->subdev_notifier = NULL;
  
diff --git a/include/media/v4l2-async.h b/include/media/v4l2-async.h
index 1592d32..fa05905 100644
--- a/include/media/v4l2-async.h
+++ b/include/media/v4l2-async.h
@@ -73,6 +73,8 @@ enum v4l2_async_match_type {
   * @match.custom.priv:
   *		Driver-specific private struct with match parameters
   *		to be used if %V4L2_ASYNC_MATCH_CUSTOM.
+ * @asd_list:	used to add struct v4l2_async_subdev objects to the
+ *		master notifier->asd_list
   * @list:	used to link struct v4l2_async_subdev objects, waiting to be
   *		probed, to a notifier->waiting list
   *
@@ -98,6 +100,7 @@ struct v4l2_async_subdev {
  
  	/* v4l2-async core private: not to be used by drivers */
  	struct list_head list;
+	struct list_head asd_list;
  };
  
  /**
@@ -127,9 +130,11 @@ struct v4l2_async_notifier_operations {
   * @v4l2_dev:	v4l2_device of the root notifier, NULL otherwise
   * @sd:		sub-device that registered the notifier, NULL otherwise
   * @parent:	parent notifier
+ * @asd_list:	master list of struct v4l2_async_subdev, replaces @subdevs
   * @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
+ * @lists_initialized: list_head's have been initialized
   */
  struct v4l2_async_notifier {
  	const struct v4l2_async_notifier_operations *ops;
@@ -139,12 +144,29 @@ struct v4l2_async_notifier {
  	struct v4l2_device *v4l2_dev;
  	struct v4l2_subdev *sd;
  	struct v4l2_async_notifier *parent;
+	struct list_head asd_list;
  	struct list_head waiting;
  	struct list_head done;
  	struct list_head list;
+	bool lists_initialized;
  };
  
  /**
+ * v4l2_async_notifier_add_subdev - Add an async subdev to the
+ *				notifier's master asd_list.
+ *
+ * @notifier: pointer to &struct v4l2_async_notifier
+ * @asd: pointer to &struct v4l2_async_subdev
+ *
+ * This can be used before registering a notifier to add an
+ * asd to the notifiers master asd_list. If the caller uses
+ * this method to compose an asd list, it must never allocate
+ * or place asd's in the @subdevs array.
+ */
+int v4l2_async_notifier_add_subdev(struct v4l2_async_notifier *notifier,
+				   struct v4l2_async_subdev *asd);
+
+/**
   * v4l2_async_notifier_register - registers a subdevice asynchronous notifier
   *
   * @v4l2_dev: pointer to &struct v4l2_device
--
2.7.4








