diff mbox series

[4/6] media: subdev: add subdev state locking

Message ID 20211217111836.225013-5-tomi.valkeinen@ideasonboard.com
State New
Headers show
Series v4l: subdev active state | expand

Commit Message

Tomi Valkeinen Dec. 17, 2021, 11:18 a.m. UTC 
The V4L2 subdevs have managed without centralized locking for the state
(previously pad_config), as the try-state is supposedly safe (although I
believe two TRY ioctls for the same fd would race), and the
active-state, and its locking, is managed by the drivers internally.

We now have active-state in a centralized position, and need locking.
Strictly speaking the locking is only needed for new drivers that use
the new state, as the current drivers continue behaving as they used to.

Add a mutex to the struct v4l2_subdev_state, along with a few helper
functions for locking/unlocking.

Signed-off-by: Tomi Valkeinen <tomi.valkeinen@ideasonboard.com>
Reviewed-by: Jacopo Mondi <jacopo+renesas@jmondi.org>
Reviewed-by: Laurent Pinchart <laurent.pinchart@ideasonboard.com>
---
 drivers/media/platform/rcar-vin/rcar-v4l2.c |  7 ++-
 drivers/media/platform/vsp1/vsp1_entity.c   |  8 +++-
 drivers/media/v4l2-core/v4l2-subdev.c       | 38 +++++++++++++---
 drivers/staging/media/tegra-video/vi.c      |  8 +++-
 include/media/v4l2-subdev.h                 | 50 ++++++++++++++++++++-
 5 files changed, 101 insertions(+), 10 deletions(-)
diff mbox series

Patch

diff --git a/drivers/media/platform/rcar-vin/rcar-v4l2.c b/drivers/media/platform/rcar-vin/rcar-v4l2.c
index 5aae01456c04..3759f4619a77 100644
--- a/drivers/media/platform/rcar-vin/rcar-v4l2.c
+++ b/drivers/media/platform/rcar-vin/rcar-v4l2.c
@@ -255,6 +255,7 @@  static int rvin_try_format(struct rvin_dev *vin, u32 which,
 {
 	struct v4l2_subdev *sd = vin_to_source(vin);
 	struct v4l2_subdev_state *sd_state;
+	static struct lock_class_key key;
 	struct v4l2_subdev_format format = {
 		.which = which,
 		.pad = vin->parallel.source_pad,
@@ -263,7 +264,11 @@  static int rvin_try_format(struct rvin_dev *vin, u32 which,
 	u32 width, height;
 	int ret;
 
-	sd_state = __v4l2_subdev_state_alloc(sd);
+	/*
+	 * FIXME: Drop this call, drivers are not supposed to use
+	 * __v4l2_subdev_state_alloc().
+	 */
+	sd_state = __v4l2_subdev_state_alloc(sd, "rvin:state->lock", &key);
 	if (IS_ERR(sd_state))
 		return PTR_ERR(sd_state);
 
diff --git a/drivers/media/platform/vsp1/vsp1_entity.c b/drivers/media/platform/vsp1/vsp1_entity.c
index 869cadc1468d..a116a3362f9e 100644
--- a/drivers/media/platform/vsp1/vsp1_entity.c
+++ b/drivers/media/platform/vsp1/vsp1_entity.c
@@ -613,6 +613,7 @@  int vsp1_entity_init(struct vsp1_device *vsp1, struct vsp1_entity *entity,
 		     const char *name, unsigned int num_pads,
 		     const struct v4l2_subdev_ops *ops, u32 function)
 {
+	static struct lock_class_key key;
 	struct v4l2_subdev *subdev;
 	unsigned int i;
 	int ret;
@@ -675,7 +676,12 @@  int vsp1_entity_init(struct vsp1_device *vsp1, struct vsp1_entity *entity,
 	 * Allocate the pad configuration to store formats and selection
 	 * rectangles.
 	 */
-	entity->config = __v4l2_subdev_state_alloc(&entity->subdev);
+	/*
+	 * FIXME: Drop this call, drivers are not supposed to use
+	 * __v4l2_subdev_state_alloc().
+	 */
+	entity->config = __v4l2_subdev_state_alloc(&entity->subdev,
+						   "vsp1:config->lock", &key);
 	if (IS_ERR(entity->config)) {
 		media_entity_cleanup(&entity->subdev.entity);
 		return PTR_ERR(entity->config);
diff --git a/drivers/media/v4l2-core/v4l2-subdev.c b/drivers/media/v4l2-core/v4l2-subdev.c
index 779d7ae2262d..5322329d396f 100644
--- a/drivers/media/v4l2-core/v4l2-subdev.c
+++ b/drivers/media/v4l2-core/v4l2-subdev.c
@@ -27,8 +27,9 @@ 
 static int subdev_fh_init(struct v4l2_subdev_fh *fh, struct v4l2_subdev *sd)
 {
 	struct v4l2_subdev_state *state;
+	static struct lock_class_key key;
 
-	state = __v4l2_subdev_state_alloc(sd);
+	state = __v4l2_subdev_state_alloc(sd, "fh->state->lock", &key);
 	if (IS_ERR(state))
 		return PTR_ERR(state);
 
@@ -914,7 +915,9 @@  int v4l2_subdev_link_validate(struct media_link *link)
 }
 EXPORT_SYMBOL_GPL(v4l2_subdev_link_validate);
 
-struct v4l2_subdev_state *__v4l2_subdev_state_alloc(struct v4l2_subdev *sd)
+struct v4l2_subdev_state *
+__v4l2_subdev_state_alloc(struct v4l2_subdev *sd, const char *lock_name,
+			  struct lock_class_key *lock_key)
 {
 	struct v4l2_subdev_state *state;
 	int ret;
@@ -923,6 +926,8 @@  struct v4l2_subdev_state *__v4l2_subdev_state_alloc(struct v4l2_subdev *sd)
 	if (!state)
 		return ERR_PTR(-ENOMEM);
 
+	__mutex_init(&state->lock, lock_name, lock_key);
+
 	if (sd->entity.num_pads) {
 		state->pads = kvmalloc_array(sd->entity.num_pads,
 					     sizeof(*state->pads),
@@ -954,6 +959,8 @@  void __v4l2_subdev_state_free(struct v4l2_subdev_state *state)
 	if (!state)
 		return;
 
+	mutex_destroy(&state->lock);
+
 	kvfree(state->pads);
 	kfree(state);
 }
@@ -988,11 +995,12 @@  void v4l2_subdev_notify_event(struct v4l2_subdev *sd,
 }
 EXPORT_SYMBOL_GPL(v4l2_subdev_notify_event);
 
-int v4l2_subdev_init_finalize(struct v4l2_subdev *sd)
+int __v4l2_subdev_init_finalize(struct v4l2_subdev *sd, const char *name,
+				struct lock_class_key *key)
 {
 	struct v4l2_subdev_state *state;
 
-	state = __v4l2_subdev_state_alloc(sd);
+	state = __v4l2_subdev_state_alloc(sd, name, key);
 	if (IS_ERR(state))
 		return PTR_ERR(state);
 
@@ -1000,7 +1008,7 @@  int v4l2_subdev_init_finalize(struct v4l2_subdev *sd)
 
 	return 0;
 }
-EXPORT_SYMBOL_GPL(v4l2_subdev_init_finalize);
+EXPORT_SYMBOL_GPL(__v4l2_subdev_init_finalize);
 
 void v4l2_subdev_cleanup(struct v4l2_subdev *sd)
 {
@@ -1008,3 +1016,23 @@  void v4l2_subdev_cleanup(struct v4l2_subdev *sd)
 	sd->active_state = NULL;
 }
 EXPORT_SYMBOL_GPL(v4l2_subdev_cleanup);
+
+struct v4l2_subdev_state *v4l2_subdev_lock_active_state(struct v4l2_subdev *sd)
+{
+	mutex_lock(&sd->active_state->lock);
+
+	return sd->active_state;
+}
+EXPORT_SYMBOL_GPL(v4l2_subdev_lock_active_state);
+
+void v4l2_subdev_lock_state(struct v4l2_subdev_state *state)
+{
+	mutex_lock(&state->lock);
+}
+EXPORT_SYMBOL_GPL(v4l2_subdev_lock_state);
+
+void v4l2_subdev_unlock_state(struct v4l2_subdev_state *state)
+{
+	mutex_unlock(&state->lock);
+}
+EXPORT_SYMBOL_GPL(v4l2_subdev_unlock_state);
diff --git a/drivers/staging/media/tegra-video/vi.c b/drivers/staging/media/tegra-video/vi.c
index b01f19e0f332..b366b56df15c 100644
--- a/drivers/staging/media/tegra-video/vi.c
+++ b/drivers/staging/media/tegra-video/vi.c
@@ -491,6 +491,7 @@  static int __tegra_channel_try_format(struct tegra_vi_channel *chan,
 				      struct v4l2_pix_format *pix)
 {
 	const struct tegra_video_format *fmtinfo;
+	static struct lock_class_key key;
 	struct v4l2_subdev *subdev;
 	struct v4l2_subdev_format fmt;
 	struct v4l2_subdev_state *sd_state;
@@ -507,7 +508,12 @@  static int __tegra_channel_try_format(struct tegra_vi_channel *chan,
 	if (!subdev)
 		return -ENODEV;
 
-	sd_state = __v4l2_subdev_state_alloc(subdev);
+	/*
+	 * FIXME: Drop this call, drivers are not supposed to use
+	 * __v4l2_subdev_state_alloc().
+	 */
+	sd_state = __v4l2_subdev_state_alloc(subdev, "tegra:state->lock",
+					     &key);
 	if (IS_ERR(sd_state))
 		return PTR_ERR(sd_state);
 	/*
diff --git a/include/media/v4l2-subdev.h b/include/media/v4l2-subdev.h
index eddf72768e10..80cd0ffb60d1 100644
--- a/include/media/v4l2-subdev.h
+++ b/include/media/v4l2-subdev.h
@@ -658,6 +658,7 @@  struct v4l2_subdev_pad_config {
 /**
  * struct v4l2_subdev_state - Used for storing subdev state information.
  *
+ * @lock: mutex for the state
  * @pads: &struct v4l2_subdev_pad_config array
  *
  * This structure only needs to be passed to the pad op if the 'which' field
@@ -665,6 +666,8 @@  struct v4l2_subdev_pad_config {
  * %V4L2_SUBDEV_FORMAT_ACTIVE it is safe to pass %NULL.
  */
 struct v4l2_subdev_state {
+	/* lock for the struct v4l2_subdev_state fields */
+	struct mutex lock;
 	struct v4l2_subdev_pad_config *pads;
 };
 
@@ -1157,10 +1160,14 @@  int v4l2_subdev_link_validate(struct media_link *link);
  * __v4l2_subdev_state_alloc - allocate v4l2_subdev_state
  *
  * @sd: pointer to &struct v4l2_subdev for which the state is being allocated.
+ * @lock_name: name of the state lock
+ * @key: lock_class_key for the lock
  *
  * Must call __v4l2_subdev_state_free() when state is no longer needed.
  */
-struct v4l2_subdev_state *__v4l2_subdev_state_alloc(struct v4l2_subdev *sd);
+struct v4l2_subdev_state *__v4l2_subdev_state_alloc(struct v4l2_subdev *sd,
+						    const char *lock_name,
+						    struct lock_class_key *key);
 
 /**
  * __v4l2_subdev_state_free - free a v4l2_subdev_state
@@ -1250,7 +1257,16 @@  void v4l2_subdev_notify_event(struct v4l2_subdev *sd,
  *
  * The user must call v4l2_subdev_cleanup() when the subdev is being removed.
  */
-int v4l2_subdev_init_finalize(struct v4l2_subdev *sd);
+#define v4l2_subdev_init_finalize(sd)                                          \
+	({                                                                     \
+		static struct lock_class_key __key;                            \
+		const char *name = KBUILD_BASENAME                             \
+			":" __stringify(__LINE__) ":subdev->state->lock";      \
+		__v4l2_subdev_init_finalize(sd, name, &__key);                 \
+	})
+
+int __v4l2_subdev_init_finalize(struct v4l2_subdev *sd, const char *name,
+				struct lock_class_key *key);
 
 /**
  * v4l2_subdev_cleanup() - Releases the resources needed by the subdevice
@@ -1275,4 +1291,34 @@  v4l2_subdev_get_active_state(struct v4l2_subdev *sd)
 	return sd->active_state;
 }
 
+/**
+ * v4l2_subdev_lock_active_state() - Locks and returns the active subdev state
+ *				     for the subdevice
+ * @sd: The subdevice
+ *
+ * Returns the locked active state for the subdevice, or NULL if the subdev
+ * does not support active state.
+ *
+ * The state must be unlocked with v4l2_subdev_unlock_state() after use.
+ */
+struct v4l2_subdev_state *v4l2_subdev_lock_active_state(struct v4l2_subdev *sd);
+
+/**
+ * v4l2_subdev_lock_state() - Locks the subdev state
+ * @state: The subdevice state
+ *
+ * Locks the given subdev state.
+ *
+ * The state must be unlocked with v4l2_subdev_unlock_state() after use.
+ */
+void v4l2_subdev_lock_state(struct v4l2_subdev_state *state);
+
+/**
+ * v4l2_subdev_unlock_state() - Unlocks the subdev state
+ * @state: The subdevice state
+ *
+ * Unlocks the given subdev state.
+ */
+void v4l2_subdev_unlock_state(struct v4l2_subdev_state *state);
+
 #endif