[PATCH v6 0/8] v4l: subdev active state

[PATCH v6 0/8] v4l: subdev active state

[Tomi Valkeinen]

Hi,

v6 of the subdev active state series. v5 can be found from:

https://lore.kernel.org/all/20220301105548.305191-1-tomi.valkeinen@ideasonboard.com/

Changes since v5:

- Fix code-block in docs
- State management wrappers (DEFINE_STATE_WRAPPER). These wrappers will handle
  the cases where the caller does not pass the active state properly.
- Added v4l2_subdev_get_fmt(). This can be used by state-enabled subdev drivers for
  v4l2_subdev_pad_ops.get_fmt.
- Drop the legacy .h file and have v4l2_subdev_call_state_active() in
  v4l2-subdev.h. The macro is now part of the "add subdev state locking" patch
  as it is used there.
- Added v4l2_subdev_get_pad_* helpers. These are temporary helpers to get rid of
  the "try" word. The v4l2_subdev_get_try_* functions should later be renamed and
  these temporary macros dropped.
- Rename v4l2_subdev_get_active_state() to v4l2_subdev_get_unlocked_active_state()
- Fix v4l2_subdev_lock_and_get_active_state() when there is no active state

I have pushed my work/test branch to:

git://git.kernel.org/pub/scm/linux/kernel/git/tomba/linux.git streams/state-work

It contains this series, ov5640 series from Jacopo, and a some hacks/fixes I
needed. The important part there is the topmost commit: "ov5640: convert to
active state", which shows how a sensor driver can be changed to support active
state.

A few notes about that patch:
- It could perhaps be cleaner if the state was passed around in certain
  functions instead of calling v4l2_subdev_get_locked_active_state() in
  multiple places.
- The driver has a private mutex, which was shared with the control handler. The
  same mutex is now also used for the states. There are not many places where
  the private mutex is used as it were, and those could be converted to just
  lock the active state.
- Only the format is handled via the state. The driver also has some
  crop/selection code, but I wasn't sure how that works.
- ov5640_get_fmt() goes away as we can just use the v4l2_subdev_get_fmt()
- The driver uses the new helper macro to get the format, instead of the "try" version, e.g.
  "fmt = v4l2_subdev_get_pad_format(&sensor->sd, state, 0);" to get the format
  for pad 0 in the given state.

 Tomi

Tomi Valkeinen (8):
  media: subdev: rename subdev-state alloc & free
  media: subdev: add active state to struct v4l2_subdev
  media: subdev: add v4l2_subdev_get_pad_* helpers
  media: subdev: pass also the active state to subdevs from ioctls
  media: subdev: add subdev state locking
  media: subdev: add locking wrappers to subdev op wrappers
  media: subdev: add v4l2_subdev_get_fmt() helper function
  media: Documentation: add documentation about subdev state

 .../driver-api/media/v4l2-subdev.rst          |  75 ++++++
 .../platform/renesas/rcar-vin/rcar-v4l2.c     |   9 +-
 .../media/platform/renesas/vsp1/vsp1_entity.c |  10 +-
 drivers/media/v4l2-core/v4l2-subdev.c         | 194 ++++++++++++---
 drivers/staging/media/tegra-video/vi.c        |  10 +-
 include/media/v4l2-subdev.h                   | 220 +++++++++++++++++-
 6 files changed, 480 insertions(+), 38 deletions(-)

-- 
2.25.1

[PATCH v6 1/8] media: subdev: rename subdev-state alloc & free

[Tomi Valkeinen]

v4l2_subdev_alloc_state() and v4l2_subdev_free_state() are not supposed
to be used by the drivers. However, we do have a few drivers that use
those at the moment, so we need to expose these functions for the time
being.

Prefix the functions with __ to mark the functions as internal.

At the same time, rename them to v4l2_subdev_state_alloc and
v4l2_subdev_state_free to match the style used for other functions like
video_device_alloc() and media_request_alloc().

Signed-off-by: Tomi Valkeinen <tomi.valkeinen@ideasonboard.com>
Reviewed-by: Laurent Pinchart <laurent.pinchart@ideasonboard.com>
Reviewed-by: Hans Verkuil <hverkuil-cisco@xs4all.nl>
Reviewed-by: Jacopo Mondi <jacopo@jmondi.org>
---
 .../media/platform/renesas/rcar-vin/rcar-v4l2.c    |  8 ++++++--
 drivers/media/platform/renesas/vsp1/vsp1_entity.c  |  8 ++++++--
 drivers/media/v4l2-core/v4l2-subdev.c              | 12 ++++++------
 drivers/staging/media/tegra-video/vi.c             |  8 ++++++--
 include/media/v4l2-subdev.h                        | 14 +++++++++-----
 5 files changed, 33 insertions(+), 17 deletions(-)

diff --git a/drivers/media/platform/renesas/rcar-vin/rcar-v4l2.c b/drivers/media/platform/renesas/rcar-vin/rcar-v4l2.c
index 2e60b9fce03b..da88f968c31a 100644
--- a/drivers/media/platform/renesas/rcar-vin/rcar-v4l2.c
+++ b/drivers/media/platform/renesas/rcar-vin/rcar-v4l2.c
@@ -263,7 +263,11 @@ static int rvin_try_format(struct rvin_dev *vin, u32 which,
 	u32 width, height;
 	int ret;
 
-	sd_state = v4l2_subdev_alloc_state(sd);
+	/*
+	 * FIXME: Drop this call, drivers are not supposed to use
+	 * __v4l2_subdev_state_alloc().
+	 */
+	sd_state = __v4l2_subdev_state_alloc(sd);
 	if (IS_ERR(sd_state))
 		return PTR_ERR(sd_state);
 
@@ -299,7 +303,7 @@ static int rvin_try_format(struct rvin_dev *vin, u32 which,
 
 	rvin_format_align(vin, pix);
 done:
-	v4l2_subdev_free_state(sd_state);
+	__v4l2_subdev_state_free(sd_state);
 
 	return ret;
 }
diff --git a/drivers/media/platform/renesas/vsp1/vsp1_entity.c b/drivers/media/platform/renesas/vsp1/vsp1_entity.c
index 823c15facd1b..c82b3fb7b89a 100644
--- a/drivers/media/platform/renesas/vsp1/vsp1_entity.c
+++ b/drivers/media/platform/renesas/vsp1/vsp1_entity.c
@@ -675,7 +675,11 @@ 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_alloc_state(&entity->subdev);
+	/*
+	 * FIXME: Drop this call, drivers are not supposed to use
+	 * __v4l2_subdev_state_alloc().
+	 */
+	entity->config = __v4l2_subdev_state_alloc(&entity->subdev);
 	if (IS_ERR(entity->config)) {
 		media_entity_cleanup(&entity->subdev.entity);
 		return PTR_ERR(entity->config);
@@ -690,6 +694,6 @@ void vsp1_entity_destroy(struct vsp1_entity *entity)
 		entity->ops->destroy(entity);
 	if (entity->subdev.ctrl_handler)
 		v4l2_ctrl_handler_free(entity->subdev.ctrl_handler);
-	v4l2_subdev_free_state(entity->config);
+	__v4l2_subdev_state_free(entity->config);
 	media_entity_cleanup(&entity->subdev.entity);
 }
diff --git a/drivers/media/v4l2-core/v4l2-subdev.c b/drivers/media/v4l2-core/v4l2-subdev.c
index 30eb50407db5..376595954db0 100644
--- a/drivers/media/v4l2-core/v4l2-subdev.c
+++ b/drivers/media/v4l2-core/v4l2-subdev.c
@@ -28,7 +28,7 @@ static int subdev_fh_init(struct v4l2_subdev_fh *fh, struct v4l2_subdev *sd)
 {
 	struct v4l2_subdev_state *state;
 
-	state = v4l2_subdev_alloc_state(sd);
+	state = __v4l2_subdev_state_alloc(sd);
 	if (IS_ERR(state))
 		return PTR_ERR(state);
 
@@ -39,7 +39,7 @@ static int subdev_fh_init(struct v4l2_subdev_fh *fh, struct v4l2_subdev *sd)
 
 static void subdev_fh_free(struct v4l2_subdev_fh *fh)
 {
-	v4l2_subdev_free_state(fh->state);
+	__v4l2_subdev_state_free(fh->state);
 	fh->state = NULL;
 }
 
@@ -862,7 +862,7 @@ int v4l2_subdev_link_validate(struct media_link *link)
 }
 EXPORT_SYMBOL_GPL(v4l2_subdev_link_validate);
 
-struct v4l2_subdev_state *v4l2_subdev_alloc_state(struct v4l2_subdev *sd)
+struct v4l2_subdev_state *__v4l2_subdev_state_alloc(struct v4l2_subdev *sd)
 {
 	struct v4l2_subdev_state *state;
 	int ret;
@@ -895,9 +895,9 @@ struct v4l2_subdev_state *v4l2_subdev_alloc_state(struct v4l2_subdev *sd)
 
 	return ERR_PTR(ret);
 }
-EXPORT_SYMBOL_GPL(v4l2_subdev_alloc_state);
+EXPORT_SYMBOL_GPL(__v4l2_subdev_state_alloc);
 
-void v4l2_subdev_free_state(struct v4l2_subdev_state *state)
+void __v4l2_subdev_state_free(struct v4l2_subdev_state *state)
 {
 	if (!state)
 		return;
@@ -905,7 +905,7 @@ void v4l2_subdev_free_state(struct v4l2_subdev_state *state)
 	kvfree(state->pads);
 	kfree(state);
 }
-EXPORT_SYMBOL_GPL(v4l2_subdev_free_state);
+EXPORT_SYMBOL_GPL(__v4l2_subdev_state_free);
 
 #endif /* CONFIG_MEDIA_CONTROLLER */
 
diff --git a/drivers/staging/media/tegra-video/vi.c b/drivers/staging/media/tegra-video/vi.c
index d1f43f465c22..07d368f345cd 100644
--- a/drivers/staging/media/tegra-video/vi.c
+++ b/drivers/staging/media/tegra-video/vi.c
@@ -507,7 +507,11 @@ static int __tegra_channel_try_format(struct tegra_vi_channel *chan,
 	if (!subdev)
 		return -ENODEV;
 
-	sd_state = v4l2_subdev_alloc_state(subdev);
+	/*
+	 * FIXME: Drop this call, drivers are not supposed to use
+	 * __v4l2_subdev_state_alloc().
+	 */
+	sd_state = __v4l2_subdev_state_alloc(subdev);
 	if (IS_ERR(sd_state))
 		return PTR_ERR(sd_state);
 	/*
@@ -558,7 +562,7 @@ static int __tegra_channel_try_format(struct tegra_vi_channel *chan,
 	v4l2_fill_pix_format(pix, &fmt.format);
 	tegra_channel_fmt_align(chan, pix, fmtinfo->bpp);
 
-	v4l2_subdev_free_state(sd_state);
+	__v4l2_subdev_state_free(sd_state);
 
 	return 0;
 }
diff --git a/include/media/v4l2-subdev.h b/include/media/v4l2-subdev.h
index 6c153b33bb04..5d6f56648ad6 100644
--- a/include/media/v4l2-subdev.h
+++ b/include/media/v4l2-subdev.h
@@ -1122,20 +1122,24 @@ int v4l2_subdev_link_validate_default(struct v4l2_subdev *sd,
 int v4l2_subdev_link_validate(struct media_link *link);
 
 /**
- * v4l2_subdev_alloc_state - allocate v4l2_subdev_state
+ * __v4l2_subdev_state_alloc - allocate v4l2_subdev_state
  *
  * @sd: pointer to &struct v4l2_subdev for which the state is being allocated.
  *
- * Must call v4l2_subdev_free_state() when state is no longer needed.
+ * Must call __v4l2_subdev_state_free() when state is no longer needed.
+ *
+ * Not to be called directly by the drivers.
  */
-struct v4l2_subdev_state *v4l2_subdev_alloc_state(struct v4l2_subdev *sd);
+struct v4l2_subdev_state *__v4l2_subdev_state_alloc(struct v4l2_subdev *sd);
 
 /**
- * v4l2_subdev_free_state - free a v4l2_subdev_state
+ * __v4l2_subdev_state_free - free a v4l2_subdev_state
  *
  * @state: v4l2_subdev_state to be freed.
+ *
+ * Not to be called directly by the drivers.
  */
-void v4l2_subdev_free_state(struct v4l2_subdev_state *state);
+void __v4l2_subdev_state_free(struct v4l2_subdev_state *state);
 
 #endif /* CONFIG_MEDIA_CONTROLLER */
 
-- 
2.25.1

[PATCH v6 2/8] media: subdev: add active state to struct v4l2_subdev

[Tomi Valkeinen]

Add a new 'active_state' field to struct v4l2_subdev to which we can
store the active state of a subdev. This will place the subdev
configuration into a known place, allowing us to use the state directly
from the v4l2 framework, thus simplifying the drivers.

Also add functions v4l2_subdev_init_finalize() and
v4l2_subdev_cleanup(), which will allocate and free the active state.
The functions are named in a generic way so that they can be also used
for other subdev initialization work.

Signed-off-by: Tomi Valkeinen <tomi.valkeinen@ideasonboard.com>
Reviewed-by: Hans Verkuil <hverkuil-cisco@xs4all.nl>
Reviewed-by: Jacopo Mondi <jacopo+renesas@jmondi.org>
Reviewed-by: Laurent Pinchart <laurent.pinchart@ideasonboard.com>
---
 drivers/media/v4l2-core/v4l2-subdev.c | 21 ++++++++++
 include/media/v4l2-subdev.h           | 58 +++++++++++++++++++++++++++
 2 files changed, 79 insertions(+)

diff --git a/drivers/media/v4l2-core/v4l2-subdev.c b/drivers/media/v4l2-core/v4l2-subdev.c
index 376595954db0..11a06e0aca0c 100644
--- a/drivers/media/v4l2-core/v4l2-subdev.c
+++ b/drivers/media/v4l2-core/v4l2-subdev.c
@@ -907,6 +907,27 @@ void __v4l2_subdev_state_free(struct v4l2_subdev_state *state)
 }
 EXPORT_SYMBOL_GPL(__v4l2_subdev_state_free);
 
+int v4l2_subdev_init_finalize(struct v4l2_subdev *sd)
+{
+	struct v4l2_subdev_state *state;
+
+	state = __v4l2_subdev_state_alloc(sd);
+	if (IS_ERR(state))
+		return PTR_ERR(state);
+
+	sd->active_state = state;
+
+	return 0;
+}
+EXPORT_SYMBOL_GPL(v4l2_subdev_init_finalize);
+
+void v4l2_subdev_cleanup(struct v4l2_subdev *sd)
+{
+	__v4l2_subdev_state_free(sd->active_state);
+	sd->active_state = NULL;
+}
+EXPORT_SYMBOL_GPL(v4l2_subdev_cleanup);
+
 #endif /* CONFIG_MEDIA_CONTROLLER */
 
 void v4l2_subdev_init(struct v4l2_subdev *sd, const struct v4l2_subdev_ops *ops)
diff --git a/include/media/v4l2-subdev.h b/include/media/v4l2-subdev.h
index 5d6f56648ad6..1bbe4383966c 100644
--- a/include/media/v4l2-subdev.h
+++ b/include/media/v4l2-subdev.h
@@ -645,6 +645,9 @@ struct v4l2_subdev_ir_ops {
  * This structure only needs to be passed to the pad op if the 'which' field
  * of the main argument is set to %V4L2_SUBDEV_FORMAT_TRY. For
  * %V4L2_SUBDEV_FORMAT_ACTIVE it is safe to pass %NULL.
+ *
+ * Note: This struct is also used in active state, and the 'try' prefix is
+ * historical and to be removed.
  */
 struct v4l2_subdev_pad_config {
 	struct v4l2_mbus_framefmt try_fmt;
@@ -885,6 +888,9 @@ struct v4l2_subdev_platform_data {
  * @subdev_notifier: A sub-device notifier implicitly registered for the sub-
  *		     device using v4l2_async_register_subdev_sensor().
  * @pdata: common part of subdevice platform data
+ * @active_state: Active state for the subdev (NULL for subdevs tracking the
+ *		  state internally). Initialized by calling
+ *		  v4l2_subdev_init_finalize().
  *
  * Each instance of a subdev driver should create this struct, either
  * stand-alone or embedded in a larger struct.
@@ -916,6 +922,19 @@ struct v4l2_subdev {
 	struct v4l2_async_notifier *notifier;
 	struct v4l2_async_notifier *subdev_notifier;
 	struct v4l2_subdev_platform_data *pdata;
+
+	/*
+	 * The fields below are private, and should only be accessed via
+	 * appropriate functions.
+	 */
+
+	/*
+	 * TODO: active_state should most likely be changed from a pointer to an
+	 * embedded field. For the time being it's kept as a pointer to more
+	 * easily catch uses of active_state in the cases where the driver
+	 * doesn't support it.
+	 */
+	struct v4l2_subdev_state *active_state;
 };
 
 
@@ -1141,6 +1160,45 @@ struct v4l2_subdev_state *__v4l2_subdev_state_alloc(struct v4l2_subdev *sd);
  */
 void __v4l2_subdev_state_free(struct v4l2_subdev_state *state);
 
+/**
+ * v4l2_subdev_init_finalize() - Finalizes the initialization of the subdevice
+ * @sd: The subdev
+ *
+ * This function finalizes the initialization of the subdev, including
+ * allocation of the active state for the subdev.
+ *
+ * This function must be called by the subdev drivers that use the centralized
+ * active state, after the subdev struct has been initialized and
+ * media_entity_pads_init() has been called, but before registering the
+ * subdev.
+ *
+ * The user must call v4l2_subdev_cleanup() when the subdev is being removed.
+ */
+int v4l2_subdev_init_finalize(struct v4l2_subdev *sd);
+
+/**
+ * v4l2_subdev_cleanup() - Releases the resources allocated by the subdevice
+ * @sd: The subdevice
+ *
+ * This function will release the resources allocated in
+ * v4l2_subdev_init_finalize.
+ */
+void v4l2_subdev_cleanup(struct v4l2_subdev *sd);
+
+/**
+ * v4l2_subdev_get_active_state() - Returns the active subdev state for
+ *				    subdevice
+ * @sd: The subdevice
+ *
+ * Returns the active state for the subdevice, or NULL if the subdev does not
+ * support active state.
+ */
+static inline struct v4l2_subdev_state *
+v4l2_subdev_get_active_state(struct v4l2_subdev *sd)
+{
+	return sd->active_state;
+}
+
 #endif /* CONFIG_MEDIA_CONTROLLER */
 
 /**
-- 
2.25.1

[PATCH v6 3/8] media: subdev: add v4l2_subdev_get_pad_* helpers

[Tomi Valkeinen]

The subdev state is now used for both try and active cases. We should
rename v4l2_subdev_get_try_* helpers to v4l2_subdev_get_pad_*, but due
to the size of that change lets add temporary wrapper helpers which can
be used in drivers that support active state.

Signed-off-by: Tomi Valkeinen <tomi.valkeinen@ideasonboard.com>
---
 include/media/v4l2-subdev.h | 10 ++++++++++
 1 file changed, 10 insertions(+)

diff --git a/include/media/v4l2-subdev.h b/include/media/v4l2-subdev.h
index 1bbe4383966c..b9587a265b32 100644
--- a/include/media/v4l2-subdev.h
+++ b/include/media/v4l2-subdev.h
@@ -1042,6 +1042,16 @@ v4l2_subdev_get_try_compose(struct v4l2_subdev *sd,
 	return &state->pads[pad].try_compose;
 }
 
+/* Temprary helpers until v4l2_subdev_get_try_* functions have been renamed */
+#define v4l2_subdev_get_pad_format(sd, state, pad) \
+	v4l2_subdev_get_try_format(sd, state, pad)
+
+#define v4l2_subdev_get_pad_crop(sd, state, pad) \
+	v4l2_subdev_get_try_crop(sd, state, pad)
+
+#define v4l2_subdev_get_pad_compose(sd, state, pad) \
+	v4l2_subdev_get_try_compose(sd, state, pad)
+
 #endif
 
 extern const struct v4l2_file_operations v4l2_subdev_fops;
-- 
2.25.1

[PATCH v6 4/8] media: subdev: pass also the active state to subdevs from ioctls

[Tomi Valkeinen]

At the moment when a subdev op is called, the TRY subdev state
(subdev_fh->state) is passed as a parameter even for the ACTIVE case, or
alternatively a NULL can be passed for ACTIVE case. This used to make
sense, as the ACTIVE state was handled internally by the subdev drivers.

We now have a state for the ACTIVE case in a standard place, and can
pass that also to the drivers. This patch changes the subdev ioctls to
either pass the TRY or ACTIVE state to the subdev.

Unfortunately many drivers call ops from other subdevs, and implicitly
pass NULL as the state, so this is just a partial solution. A coccinelle
spatch could perhaps be created which fixes the drivers' subdev calls.

For all current upstream drivers this doesn't matter, as they do not
expect to get a valid state for ACTIVE case. But future drivers which
support multiplexed streaming and routing will depend on getting a state
for both active and try cases.

For new drivers we can mandate that the pipelines where the drivers are
used need to pass the state properly, or preferably, not call such
subdev ops at all.

However, if an existing subdev driver is changed to support multiplexed
streams, the driver has to consider cases where its ops will be called
with NULL state. The problem can easily be solved by using the
v4l2_subdev_lock_and_return_state() helper, introduced in a follow up
patch.

Signed-off-by: Tomi Valkeinen <tomi.valkeinen@ideasonboard.com>
Reviewed-by: Hans Verkuil <hverkuil-cisco@xs4all.nl>
Reviewed-by: Jacopo Mondi <jacopo+renesas@jmondi.org>
Reviewed-by: Laurent Pinchart <laurent.pinchart@ideasonboard.com>
---
 drivers/media/v4l2-core/v4l2-subdev.c | 64 ++++++++++++++++++++++-----
 1 file changed, 54 insertions(+), 10 deletions(-)

diff --git a/drivers/media/v4l2-core/v4l2-subdev.c b/drivers/media/v4l2-core/v4l2-subdev.c
index 11a06e0aca0c..b67bbce82612 100644
--- a/drivers/media/v4l2-core/v4l2-subdev.c
+++ b/drivers/media/v4l2-core/v4l2-subdev.c
@@ -345,6 +345,44 @@ const struct v4l2_subdev_ops v4l2_subdev_call_wrappers = {
 EXPORT_SYMBOL(v4l2_subdev_call_wrappers);
 
 #if defined(CONFIG_VIDEO_V4L2_SUBDEV_API)
+
+static struct v4l2_subdev_state *
+subdev_ioctl_get_state(struct v4l2_subdev *sd, struct v4l2_subdev_fh *subdev_fh,
+		       unsigned int cmd, void *arg)
+{
+	u32 which;
+
+	switch (cmd) {
+	default:
+		return NULL;
+	case VIDIOC_SUBDEV_G_FMT:
+	case VIDIOC_SUBDEV_S_FMT:
+		which = ((struct v4l2_subdev_format *)arg)->which;
+		break;
+	case VIDIOC_SUBDEV_G_CROP:
+	case VIDIOC_SUBDEV_S_CROP:
+		which = ((struct v4l2_subdev_crop *)arg)->which;
+		break;
+	case VIDIOC_SUBDEV_ENUM_MBUS_CODE:
+		which = ((struct v4l2_subdev_mbus_code_enum *)arg)->which;
+		break;
+	case VIDIOC_SUBDEV_ENUM_FRAME_SIZE:
+		which = ((struct v4l2_subdev_frame_size_enum *)arg)->which;
+		break;
+	case VIDIOC_SUBDEV_ENUM_FRAME_INTERVAL:
+		which = ((struct v4l2_subdev_frame_interval_enum *)arg)->which;
+		break;
+	case VIDIOC_SUBDEV_G_SELECTION:
+	case VIDIOC_SUBDEV_S_SELECTION:
+		which = ((struct v4l2_subdev_selection *)arg)->which;
+		break;
+	}
+
+	return which == V4L2_SUBDEV_FORMAT_TRY ?
+			     subdev_fh->state :
+			     v4l2_subdev_get_active_state(sd);
+}
+
 static long subdev_do_ioctl(struct file *file, unsigned int cmd, void *arg)
 {
 	struct video_device *vdev = video_devdata(file);
@@ -352,8 +390,11 @@ static long subdev_do_ioctl(struct file *file, unsigned int cmd, void *arg)
 	struct v4l2_fh *vfh = file->private_data;
 	struct v4l2_subdev_fh *subdev_fh = to_v4l2_subdev_fh(vfh);
 	bool ro_subdev = test_bit(V4L2_FL_SUBDEV_RO_DEVNODE, &vdev->flags);
+	struct v4l2_subdev_state *state;
 	int rval;
 
+	state = subdev_ioctl_get_state(sd, subdev_fh, cmd, arg);
+
 	switch (cmd) {
 	case VIDIOC_SUBDEV_QUERYCAP: {
 		struct v4l2_subdev_capability *cap = arg;
@@ -476,7 +517,7 @@ static long subdev_do_ioctl(struct file *file, unsigned int cmd, void *arg)
 
 		memset(format->reserved, 0, sizeof(format->reserved));
 		memset(format->format.reserved, 0, sizeof(format->format.reserved));
-		return v4l2_subdev_call(sd, pad, get_fmt, subdev_fh->state, format);
+		return v4l2_subdev_call(sd, pad, get_fmt, state, format);
 	}
 
 	case VIDIOC_SUBDEV_S_FMT: {
@@ -487,7 +528,7 @@ static long subdev_do_ioctl(struct file *file, unsigned int cmd, void *arg)
 
 		memset(format->reserved, 0, sizeof(format->reserved));
 		memset(format->format.reserved, 0, sizeof(format->format.reserved));
-		return v4l2_subdev_call(sd, pad, set_fmt, subdev_fh->state, format);
+		return v4l2_subdev_call(sd, pad, set_fmt, state, format);
 	}
 
 	case VIDIOC_SUBDEV_G_CROP: {
@@ -501,7 +542,7 @@ static long subdev_do_ioctl(struct file *file, unsigned int cmd, void *arg)
 		sel.target = V4L2_SEL_TGT_CROP;
 
 		rval = v4l2_subdev_call(
-			sd, pad, get_selection, subdev_fh->state, &sel);
+			sd, pad, get_selection, state, &sel);
 
 		crop->rect = sel.r;
 
@@ -523,7 +564,7 @@ static long subdev_do_ioctl(struct file *file, unsigned int cmd, void *arg)
 		sel.r = crop->rect;
 
 		rval = v4l2_subdev_call(
-			sd, pad, set_selection, subdev_fh->state, &sel);
+			sd, pad, set_selection, state, &sel);
 
 		crop->rect = sel.r;
 
@@ -534,7 +575,7 @@ static long subdev_do_ioctl(struct file *file, unsigned int cmd, void *arg)
 		struct v4l2_subdev_mbus_code_enum *code = arg;
 
 		memset(code->reserved, 0, sizeof(code->reserved));
-		return v4l2_subdev_call(sd, pad, enum_mbus_code, subdev_fh->state,
+		return v4l2_subdev_call(sd, pad, enum_mbus_code, state,
 					code);
 	}
 
@@ -542,7 +583,7 @@ static long subdev_do_ioctl(struct file *file, unsigned int cmd, void *arg)
 		struct v4l2_subdev_frame_size_enum *fse = arg;
 
 		memset(fse->reserved, 0, sizeof(fse->reserved));
-		return v4l2_subdev_call(sd, pad, enum_frame_size, subdev_fh->state,
+		return v4l2_subdev_call(sd, pad, enum_frame_size, state,
 					fse);
 	}
 
@@ -567,7 +608,7 @@ static long subdev_do_ioctl(struct file *file, unsigned int cmd, void *arg)
 		struct v4l2_subdev_frame_interval_enum *fie = arg;
 
 		memset(fie->reserved, 0, sizeof(fie->reserved));
-		return v4l2_subdev_call(sd, pad, enum_frame_interval, subdev_fh->state,
+		return v4l2_subdev_call(sd, pad, enum_frame_interval, state,
 					fie);
 	}
 
@@ -576,7 +617,7 @@ static long subdev_do_ioctl(struct file *file, unsigned int cmd, void *arg)
 
 		memset(sel->reserved, 0, sizeof(sel->reserved));
 		return v4l2_subdev_call(
-			sd, pad, get_selection, subdev_fh->state, sel);
+			sd, pad, get_selection, state, sel);
 	}
 
 	case VIDIOC_SUBDEV_S_SELECTION: {
@@ -587,7 +628,7 @@ static long subdev_do_ioctl(struct file *file, unsigned int cmd, void *arg)
 
 		memset(sel->reserved, 0, sizeof(sel->reserved));
 		return v4l2_subdev_call(
-			sd, pad, set_selection, subdev_fh->state, sel);
+			sd, pad, set_selection, state, sel);
 	}
 
 	case VIDIOC_G_EDID: {
@@ -821,10 +862,13 @@ v4l2_subdev_link_validate_get_format(struct media_pad *pad,
 	if (is_media_entity_v4l2_subdev(pad->entity)) {
 		struct v4l2_subdev *sd =
 			media_entity_to_v4l2_subdev(pad->entity);
+		struct v4l2_subdev_state *state;
+
+		state = v4l2_subdev_get_active_state(sd);
 
 		fmt->which = V4L2_SUBDEV_FORMAT_ACTIVE;
 		fmt->pad = pad->index;
-		return v4l2_subdev_call(sd, pad, get_fmt, NULL, fmt);
+		return v4l2_subdev_call(sd, pad, get_fmt, state, fmt);
 	}
 
 	WARN(pad->entity->function != MEDIA_ENT_F_IO_V4L,
-- 
2.25.1

[PATCH v6 5/8] media: subdev: add subdev state locking

[Tomi Valkeinen]

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.

However, active-state locking is complicated by the fact that currently
the real active-state of a subdev is split into multiple parts: the new
v4l2_subdev_state, subdev control state, and subdev's internal state.

In the future all these three states should be combined into one state
(the v4l2_subdev_state), and then a single lock for the state should be
sufficient.

But to solve the current split-state situation we need to share locks
between the three states. This is accomplished by using the same lock
management as the control handler does: we use a pointer to a mutex,
allowing the driver to override the default mutex. Thus the driver can
do e.g.:

sd->state_lock = sd->ctrl_handler->lock;

before calling v4l2_subdev_init_finalize(), resulting in sharing the
same lock between the states and the controls.

The locking model for active-state is such that any subdev op that gets
the state as a parameter expects the state to be already locked by the
caller, and expects the caller to release the lock.

Signed-off-by: Tomi Valkeinen <tomi.valkeinen@ideasonboard.com>
Reviewed-by: Laurent Pinchart <laurent.pinchart@ideasonboard.com>
---
 .../platform/renesas/rcar-vin/rcar-v4l2.c     |   3 +-
 .../media/platform/renesas/vsp1/vsp1_entity.c |   4 +-
 drivers/media/v4l2-core/v4l2-subdev.c         |  63 ++++++---
 drivers/staging/media/tegra-video/vi.c        |   4 +-
 include/media/v4l2-subdev.h                   | 133 +++++++++++++++++-
 5 files changed, 181 insertions(+), 26 deletions(-)

diff --git a/drivers/media/platform/renesas/rcar-vin/rcar-v4l2.c b/drivers/media/platform/renesas/rcar-vin/rcar-v4l2.c
index da88f968c31a..3759f4619a77 100644
--- a/drivers/media/platform/renesas/rcar-vin/rcar-v4l2.c
+++ b/drivers/media/platform/renesas/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,
@@ -267,7 +268,7 @@ static int rvin_try_format(struct rvin_dev *vin, u32 which,
 	 * FIXME: Drop this call, drivers are not supposed to use
 	 * __v4l2_subdev_state_alloc().
 	 */
-	sd_state = __v4l2_subdev_state_alloc(sd);
+	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/renesas/vsp1/vsp1_entity.c b/drivers/media/platform/renesas/vsp1/vsp1_entity.c
index c82b3fb7b89a..a116a3362f9e 100644
--- a/drivers/media/platform/renesas/vsp1/vsp1_entity.c
+++ b/drivers/media/platform/renesas/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;
@@ -679,7 +680,8 @@ int vsp1_entity_init(struct vsp1_device *vsp1, struct vsp1_entity *entity,
 	 * FIXME: Drop this call, drivers are not supposed to use
 	 * __v4l2_subdev_state_alloc().
 	 */
-	entity->config = __v4l2_subdev_state_alloc(&entity->subdev);
+	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 b67bbce82612..824424f0a741 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);
 
@@ -380,21 +381,18 @@ subdev_ioctl_get_state(struct v4l2_subdev *sd, struct v4l2_subdev_fh *subdev_fh,
 
 	return which == V4L2_SUBDEV_FORMAT_TRY ?
 			     subdev_fh->state :
-			     v4l2_subdev_get_active_state(sd);
+			     v4l2_subdev_get_unlocked_active_state(sd);
 }
 
-static long subdev_do_ioctl(struct file *file, unsigned int cmd, void *arg)
+static long subdev_do_ioctl(struct file *file, unsigned int cmd, void *arg,
+			    struct v4l2_subdev_state *state)
 {
 	struct video_device *vdev = video_devdata(file);
 	struct v4l2_subdev *sd = vdev_to_v4l2_subdev(vdev);
 	struct v4l2_fh *vfh = file->private_data;
-	struct v4l2_subdev_fh *subdev_fh = to_v4l2_subdev_fh(vfh);
 	bool ro_subdev = test_bit(V4L2_FL_SUBDEV_RO_DEVNODE, &vdev->flags);
-	struct v4l2_subdev_state *state;
 	int rval;
 
-	state = subdev_ioctl_get_state(sd, subdev_fh, cmd, arg);
-
 	switch (cmd) {
 	case VIDIOC_SUBDEV_QUERYCAP: {
 		struct v4l2_subdev_capability *cap = arg;
@@ -707,8 +705,24 @@ static long subdev_do_ioctl_lock(struct file *file, unsigned int cmd, void *arg)
 
 	if (lock && mutex_lock_interruptible(lock))
 		return -ERESTARTSYS;
-	if (video_is_registered(vdev))
-		ret = subdev_do_ioctl(file, cmd, arg);
+
+	if (video_is_registered(vdev)) {
+		struct v4l2_subdev *sd = vdev_to_v4l2_subdev(vdev);
+		struct v4l2_fh *vfh = file->private_data;
+		struct v4l2_subdev_fh *subdev_fh = to_v4l2_subdev_fh(vfh);
+		struct v4l2_subdev_state *state;
+
+		state = subdev_ioctl_get_state(sd, subdev_fh, cmd, arg);
+
+		if (state)
+			v4l2_subdev_lock_state(state);
+
+		ret = subdev_do_ioctl(file, cmd, arg, state);
+
+		if (state)
+			v4l2_subdev_unlock_state(state);
+	}
+
 	if (lock)
 		mutex_unlock(lock);
 	return ret;
@@ -862,13 +876,10 @@ v4l2_subdev_link_validate_get_format(struct media_pad *pad,
 	if (is_media_entity_v4l2_subdev(pad->entity)) {
 		struct v4l2_subdev *sd =
 			media_entity_to_v4l2_subdev(pad->entity);
-		struct v4l2_subdev_state *state;
-
-		state = v4l2_subdev_get_active_state(sd);
 
 		fmt->which = V4L2_SUBDEV_FORMAT_ACTIVE;
 		fmt->pad = pad->index;
-		return v4l2_subdev_call(sd, pad, get_fmt, state, fmt);
+		return v4l2_subdev_call_state_active(sd, pad, get_fmt, fmt);
 	}
 
 	WARN(pad->entity->function != MEDIA_ENT_F_IO_V4L,
@@ -906,7 +917,9 @@ 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;
@@ -915,6 +928,12 @@ 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->state_lock)
+		state->lock = sd->state_lock;
+	else
+		state->lock = &state->_lock;
+
 	if (sd->entity.num_pads) {
 		state->pads = kvmalloc_array(sd->entity.num_pads,
 					     sizeof(*state->pads),
@@ -925,7 +944,14 @@ struct v4l2_subdev_state *__v4l2_subdev_state_alloc(struct v4l2_subdev *sd)
 		}
 	}
 
+	/*
+	 * There can be no race at this point, but we lock the state anyway to
+	 * satisfy lockdep checks.
+	 */
+	v4l2_subdev_lock_state(state);
 	ret = v4l2_subdev_call(sd, pad, init_cfg, state);
+	v4l2_subdev_unlock_state(state);
+
 	if (ret < 0 && ret != -ENOIOCTLCMD)
 		goto err;
 
@@ -946,16 +972,19 @@ void __v4l2_subdev_state_free(struct v4l2_subdev_state *state)
 	if (!state)
 		return;
 
+	mutex_destroy(&state->_lock);
+
 	kvfree(state->pads);
 	kfree(state);
 }
 EXPORT_SYMBOL_GPL(__v4l2_subdev_state_free);
 
-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);
 
@@ -963,7 +992,7 @@ 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)
 {
diff --git a/drivers/staging/media/tegra-video/vi.c b/drivers/staging/media/tegra-video/vi.c
index 07d368f345cd..8e184aa4c252 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;
@@ -511,7 +512,8 @@ static int __tegra_channel_try_format(struct tegra_vi_channel *chan,
 	 * FIXME: Drop this call, drivers are not supposed to use
 	 * __v4l2_subdev_state_alloc().
 	 */
-	sd_state = __v4l2_subdev_state_alloc(subdev);
+	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 b9587a265b32..700ce376b22c 100644
--- a/include/media/v4l2-subdev.h
+++ b/include/media/v4l2-subdev.h
@@ -658,6 +658,8 @@ struct v4l2_subdev_pad_config {
 /**
  * struct v4l2_subdev_state - Used for storing subdev state information.
  *
+ * @_lock: default for 'lock'
+ * @lock: mutex for the state. May be replaced by the user.
  * @pads: &struct v4l2_subdev_pad_config array
  *
  * This structure only needs to be passed to the pad op if the 'which' field
@@ -665,6 +667,9 @@ 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 mutex *lock;
 	struct v4l2_subdev_pad_config *pads;
 };
 
@@ -888,6 +893,9 @@ struct v4l2_subdev_platform_data {
  * @subdev_notifier: A sub-device notifier implicitly registered for the sub-
  *		     device using v4l2_async_register_subdev_sensor().
  * @pdata: common part of subdevice platform data
+ * @state_lock: A pointer to a lock used for all the subdev's states, set by the
+ *		driver. This is	optional. If NULL, each state instance will get
+ *		a lock of its own.
  * @active_state: Active state for the subdev (NULL for subdevs tracking the
  *		  state internally). Initialized by calling
  *		  v4l2_subdev_init_finalize().
@@ -922,6 +930,7 @@ struct v4l2_subdev {
 	struct v4l2_async_notifier *notifier;
 	struct v4l2_async_notifier *subdev_notifier;
 	struct v4l2_subdev_platform_data *pdata;
+	struct mutex *state_lock;
 
 	/*
 	 * The fields below are private, and should only be accessed via
@@ -1154,12 +1163,16 @@ 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.
  *
  * Not to be called directly by the drivers.
  */
-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
@@ -1184,7 +1197,16 @@ void __v4l2_subdev_state_free(struct v4l2_subdev_state *state);
  *
  * 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__) ":sd->active_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 allocated by the subdevice
@@ -1196,16 +1218,85 @@ int v4l2_subdev_init_finalize(struct v4l2_subdev *sd);
 void v4l2_subdev_cleanup(struct v4l2_subdev *sd);
 
 /**
- * v4l2_subdev_get_active_state() - Returns the active subdev state for
- *				    subdevice
+ * 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.
+ */
+static inline void v4l2_subdev_lock_state(struct v4l2_subdev_state *state)
+{
+	mutex_lock(state->lock);
+}
+
+/**
+ * v4l2_subdev_unlock_state() - Unlocks the subdev state
+ * @state: The subdevice state
+ *
+ * Unlocks the given subdev state.
+ */
+static inline void v4l2_subdev_unlock_state(struct v4l2_subdev_state *state)
+{
+	mutex_unlock(state->lock);
+}
+
+/**
+ * v4l2_subdev_get_unlocked_active_state() - Checks that the active subdev state
+ *					     is unlocked and returns it
+ * @sd: The subdevice
+ *
+ * Returns the active state for the subdevice, or NULL if the subdev does not
+ * support active state. If the state is not NULL, calls
+ * lockdep_assert_not_held() to issue a warning if the state is locked.
+ *
+ * This function is to be used e.g. when getting the active state for the sole
+ * purpose of passing it forward, without accessing the state fields.
+ */
+static inline struct v4l2_subdev_state *
+v4l2_subdev_get_unlocked_active_state(struct v4l2_subdev *sd)
+{
+	if (sd->active_state)
+		lockdep_assert_not_held(sd->active_state->lock);
+	return sd->active_state;
+}
+
+/**
+ * v4l2_subdev_get_locked_active_state() - Checks that the active subdev state
+ *					   is locked and returns it
+ *
  * @sd: The subdevice
  *
  * Returns the active state for the subdevice, or NULL if the subdev does not
- * support active state.
+ * support active state. If the state is not NULL, calls lockdep_assert_held()
+ * to issue a warning if the state is not locked.
+ *
+ * This function is to be used when the caller knows that the active state is
+ * already locked.
+ */
+static inline struct v4l2_subdev_state *
+v4l2_subdev_get_locked_active_state(struct v4l2_subdev *sd)
+{
+	if (sd->active_state)
+		lockdep_assert_held(sd->active_state->lock);
+	return sd->active_state;
+}
+
+/**
+ * v4l2_subdev_lock_and_get_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.
  */
 static inline struct v4l2_subdev_state *
-v4l2_subdev_get_active_state(struct v4l2_subdev *sd)
+v4l2_subdev_lock_and_get_active_state(struct v4l2_subdev *sd)
 {
+	if (sd->active_state)
+		v4l2_subdev_lock_state(sd->active_state);
 	return sd->active_state;
 }
 
@@ -1252,6 +1343,36 @@ extern const struct v4l2_subdev_ops v4l2_subdev_call_wrappers;
 		__result;						\
 	})
 
+/**
+ * v4l2_subdev_call_state_active - call an operation of a v4l2_subdev which
+ *				   takes state as a parameter, passing the
+ *				   subdev its active state.
+ *
+ * @sd: pointer to the &struct v4l2_subdev
+ * @o: name of the element at &struct v4l2_subdev_ops that contains @f.
+ *     Each element there groups a set of callbacks functions.
+ * @f: callback function to be called.
+ *     The callback functions are defined in groups, according to
+ *     each element at &struct v4l2_subdev_ops.
+ * @args: arguments for @f.
+ *
+ * This is similar to v4l2_subdev_call(), except that this version can only be
+ * used for ops that take a subdev state as a parameter. The macro will get the
+ * active state, lock it before calling the op and unlock it after the call.
+ */
+#define v4l2_subdev_call_state_active(sd, o, f, args...)		\
+	({								\
+		int __result;						\
+		struct v4l2_subdev_state *state;			\
+		state = v4l2_subdev_get_unlocked_active_state(sd);	\
+		if (state)						\
+			v4l2_subdev_lock_state(state);			\
+		__result = v4l2_subdev_call(sd, o, f, state, ##args);	\
+		if (state)						\
+			v4l2_subdev_unlock_state(state);		\
+		__result;						\
+	})
+
 /**
  * v4l2_subdev_has_op - Checks if a subdev defines a certain operation.
  *
-- 
2.25.1

[PATCH v6 6/8] media: subdev: add locking wrappers to subdev op wrappers

[Tomi Valkeinen]

It is common that media drivers call subdev ops in source subdevs, and
pass NULL as the state. This was the way to indicate that the callee
should use the callee's private active state.

E.g.:

v4l2_subdev_call(priv->source_sd, pad, get_fmt, NULL, &sd_fmt);

Now that we have a real subdev active state in the v4l2_subdev struct,
we want the caller to pass a proper state (when available). And
furthermore, the state should be locked.

This would mean changing all the callers, which is the long term goal.

To fix this issue in the short term, let's add an extra wrapper layer to
all v4l2_subdev_call_pad_wrappers which deal with states. These wrappers
handle the state == NULL case by using the locked active state instead
(when available).

Signed-off-by: Tomi Valkeinen <tomi.valkeinen@ideasonboard.com>
---
 drivers/media/v4l2-core/v4l2-subdev.c | 42 ++++++++++++++++++++++-----
 1 file changed, 35 insertions(+), 7 deletions(-)

diff --git a/drivers/media/v4l2-core/v4l2-subdev.c b/drivers/media/v4l2-core/v4l2-subdev.c
index 824424f0a741..d8d1c9ef4dc4 100644
--- a/drivers/media/v4l2-core/v4l2-subdev.c
+++ b/drivers/media/v4l2-core/v4l2-subdev.c
@@ -319,14 +319,42 @@ static int call_get_mbus_config(struct v4l2_subdev *sd, unsigned int pad,
 	       sd->ops->pad->get_mbus_config(sd, pad, config);
 }
 
+/*
+ * Create state-management wrapper for pad ops dealing with subdev state. The
+ * wrapper handles the case where the caller does not provide the called
+ * subdev's state. This should be removed when all the callers are fixed.
+ */
+#define DEFINE_STATE_WRAPPER(f, arg_type)                                  \
+	static int call_##f##_state(struct v4l2_subdev *sd,                \
+				    struct v4l2_subdev_state *_state,      \
+				    arg_type *format)                      \
+	{                                                                  \
+		struct v4l2_subdev_state *state = _state;                  \
+		int ret;                                                   \
+		if (!_state)                                               \
+			state = v4l2_subdev_lock_and_get_active_state(sd); \
+		ret = call_##f(sd, state, format);                         \
+		if (!_state && state)                                      \
+			v4l2_subdev_unlock_state(state);                   \
+		return ret;                                                \
+	}
+
+DEFINE_STATE_WRAPPER(get_fmt, struct v4l2_subdev_format);
+DEFINE_STATE_WRAPPER(set_fmt, struct v4l2_subdev_format);
+DEFINE_STATE_WRAPPER(enum_mbus_code, struct v4l2_subdev_mbus_code_enum);
+DEFINE_STATE_WRAPPER(enum_frame_size, struct v4l2_subdev_frame_size_enum);
+DEFINE_STATE_WRAPPER(enum_frame_interval, struct v4l2_subdev_frame_interval_enum);
+DEFINE_STATE_WRAPPER(get_selection, struct v4l2_subdev_selection);
+DEFINE_STATE_WRAPPER(set_selection, struct v4l2_subdev_selection);
+
 static const struct v4l2_subdev_pad_ops v4l2_subdev_call_pad_wrappers = {
-	.get_fmt		= call_get_fmt,
-	.set_fmt		= call_set_fmt,
-	.enum_mbus_code		= call_enum_mbus_code,
-	.enum_frame_size	= call_enum_frame_size,
-	.enum_frame_interval	= call_enum_frame_interval,
-	.get_selection		= call_get_selection,
-	.set_selection		= call_set_selection,
+	.get_fmt		= call_get_fmt_state,
+	.set_fmt		= call_set_fmt_state,
+	.enum_mbus_code		= call_enum_mbus_code_state,
+	.enum_frame_size	= call_enum_frame_size_state,
+	.enum_frame_interval	= call_enum_frame_interval_state,
+	.get_selection		= call_get_selection_state,
+	.set_selection		= call_set_selection_state,
 	.get_edid		= call_get_edid,
 	.set_edid		= call_set_edid,
 	.dv_timings_cap		= call_dv_timings_cap,
-- 
2.25.1

[PATCH v6 7/8] media: subdev: add v4l2_subdev_get_fmt() helper function

[Tomi Valkeinen]

Add v4l2_subdev_get_fmt() helper function which implements
v4l2_subdev_pad_ops.get_fmt using active state. Subdev drivers that
support active state and do not need to do anything special in their
get_fmt op can use this helper directly for v4l2_subdev_pad_ops.get_fmt.

Signed-off-by: Tomi Valkeinen <tomi.valkeinen@ideasonboard.com>
---
 drivers/media/v4l2-core/v4l2-subdev.c | 18 ++++++++++++++++++
 include/media/v4l2-subdev.h           | 17 +++++++++++++++++
 2 files changed, 35 insertions(+)

diff --git a/drivers/media/v4l2-core/v4l2-subdev.c b/drivers/media/v4l2-core/v4l2-subdev.c
index d8d1c9ef4dc4..cbc5ebff0656 100644
--- a/drivers/media/v4l2-core/v4l2-subdev.c
+++ b/drivers/media/v4l2-core/v4l2-subdev.c
@@ -1029,6 +1029,24 @@ void v4l2_subdev_cleanup(struct v4l2_subdev *sd)
 }
 EXPORT_SYMBOL_GPL(v4l2_subdev_cleanup);
 
+int v4l2_subdev_get_fmt(struct v4l2_subdev *sd, struct v4l2_subdev_state *state,
+			struct v4l2_subdev_format *format)
+{
+	struct v4l2_mbus_framefmt *fmt;
+
+	if (format->pad >= sd->entity.num_pads)
+		return -EINVAL;
+
+	fmt = v4l2_subdev_get_try_format(sd, state, format->pad);
+	if (!fmt)
+		return -EINVAL;
+
+	format->format = *fmt;
+
+	return 0;
+}
+EXPORT_SYMBOL_GPL(v4l2_subdev_get_fmt);
+
 #endif /* CONFIG_MEDIA_CONTROLLER */
 
 void v4l2_subdev_init(struct v4l2_subdev *sd, const struct v4l2_subdev_ops *ops)
diff --git a/include/media/v4l2-subdev.h b/include/media/v4l2-subdev.h
index 700ce376b22c..491bdbb1670c 100644
--- a/include/media/v4l2-subdev.h
+++ b/include/media/v4l2-subdev.h
@@ -1300,6 +1300,23 @@ v4l2_subdev_lock_and_get_active_state(struct v4l2_subdev *sd)
 	return sd->active_state;
 }
 
+/**
+ * v4l2_subdev_get_fmt() - Fill format based on state
+ * @sd: subdevice
+ * @state: subdevice state
+ * @format: pointer to &struct v4l2_subdev_format
+ *
+ * Fill @format->format field based on the information in the @format struct.
+ *
+ * This function can be used by the subdev drivers which support active state to
+ * implement v4l2_subdev_pad_ops.get_fmt if the subdev driver does not need to
+ * do anything special in their get_fmt op.
+ *
+ * Returns 0 on success, error value otherwise.
+ */
+int v4l2_subdev_get_fmt(struct v4l2_subdev *sd, struct v4l2_subdev_state *state,
+			struct v4l2_subdev_format *format);
+
 #endif /* CONFIG_MEDIA_CONTROLLER */
 
 /**
-- 
2.25.1

[PATCH v6 8/8] media: Documentation: add documentation about subdev state

[Tomi Valkeinen]

Add documentation about centrally managed subdev state.

Signed-off-by: Tomi Valkeinen <tomi.valkeinen@ideasonboard.com>
Reviewed-by: Jacopo Mondi <jacopo+renesas@jmondi.org>
Reviewed-by: Hans Verkuil <hverkuil-cisco@xs4all.nl>
Reviewed-by: Laurent Pinchart <laurent.pinchart@ideasonboard.com>
---
 .../driver-api/media/v4l2-subdev.rst          | 75 +++++++++++++++++++
 1 file changed, 75 insertions(+)

diff --git a/Documentation/driver-api/media/v4l2-subdev.rst b/Documentation/driver-api/media/v4l2-subdev.rst
index 08ea2673b19e..7fa950b1bff0 100644
--- a/Documentation/driver-api/media/v4l2-subdev.rst
+++ b/Documentation/driver-api/media/v4l2-subdev.rst
@@ -518,6 +518,81 @@ The :c:func:`v4l2_i2c_new_subdev` function will call
 :c:type:`i2c_board_info` structure using the ``client_type`` and the
 ``addr`` to fill it.
 
+Centrally managed subdev active state
+-------------------------------------
+
+Traditionally V4L2 subdev drivers maintained internal state for the active
+device configuration. This is often implemented as e.g. an array of struct
+v4l2_mbus_framefmt, one entry for each pad, and similarly for crop and compose
+rectangles.
+
+In addition to the active configuration, each subdev file handle has an array of
+struct v4l2_subdev_pad_config, managed by the V4L2 core, which contains the try
+configuration.
+
+To simplify the subdev drivers the V4L2 subdev API now optionally supports a
+centrally managed active configuration represented by
+:c:type:`v4l2_subdev_state`. One instance of state, which contains the active
+device configuration, is stored in the sub-device itself as part of
+the :c:type:`v4l2_subdev` structure, while the core associates a try state to
+each open file handle, to store the try configuration related to that file
+handle.
+
+Sub-device drivers can opt-in and use state to manage their active configuration
+by initializing the subdevice state with a call to v4l2_subdev_init_finalize()
+before registering the sub-device. They must also call v4l2_subdev_cleanup()
+to release all the allocated resources before unregistering the sub-device.
+The core automatically allocates and initializes a state for each open file
+handle to store the try configurations and frees it when closing the file
+handle.
+
+V4L2 sub-device operations that use both the :ref:`ACTIVE and TRY formats
+<v4l2-subdev-format-whence>` receive the correct state to operate on through
+the 'state' parameter. The state must be locked and unlocked by the
+caller by calling :c:func:`v4l2_subdev_lock_state()` and
+:c:func:`v4l2_subdev_unlock_state()`. The caller can do so by calling the subdev
+operation through the :c:func:`v4l2_subdev_call_state_active()` macro.
+
+Operations that do not receive a state parameter implicitly operate on the
+subdevice active state, which drivers can exclusively access by
+calling :c:func:`v4l2_subdev_lock_and_get_active_state()`. The sub-device active
+state must equally be released by calling :c:func:`v4l2_subdev_unlock_state()`.
+
+Drivers must never manually access the state stored in the :c:type:`v4l2_subdev`
+or in the file handle without going through the designated helpers.
+
+While the V4L2 core passes the correct try or active state to the
+subdevice operations, some existing device drivers pass a NULL state
+when calling operations with :c:func:`v4l2_subdev_call()`. This legacy
+construct causes issues with subdevice drivers that let the V4L2 core
+manage the active state, as they expect to receive the appropriate state
+as a parameter. To help the conversion of subdevice drivers to a managed
+active state without having to convert all callers at the same time, the
+:c:func:`v4l2_subdev_lock_and_return_state()` helper function can be
+used by subdevice drivers to retrieve the active state if a NULL state
+is passed to the subdevice operation.
+
+:c:func:`v4l2_subdev_lock_and_return_state()` should only be used when porting
+an existing driver to the new state management when it cannot be guaranteed
+that the current callers will pass the state properly. The function prints a
+notice when the passed state is NULL to encourage the porting of the callers
+to the new state management.
+
+The whole subdev state is in reality split into three parts: the
+v4l2_subdev_state, subdev controls and subdev driver's internal state. In the
+future these parts should be combined into a single state. For the time being
+we need a way to handle the locking for these parts. This can be accomplished
+by sharing a lock. The v4l2_ctrl_handler already supports this via its 'lock'
+pointer and the same model is used with states. The driver can do the following
+before calling v4l2_subdev_init_finalize():
+
+.. code-block:: c
+
+	sd->ctrl_handler->lock = &priv->mutex;
+	sd->state_lock = &priv->mutex;
+
+This shares the driver's private mutex between the controls and the states.
+
 V4L2 sub-device functions and data structures
 ---------------------------------------------
 
-- 
2.25.1

Re: [PATCH v6 3/8] media: subdev: add v4l2_subdev_get_pad_* helpers

[Hans Verkuil]

On 24/03/2022 09:00, Tomi Valkeinen wrote:
> The subdev state is now used for both try and active cases. We should
> rename v4l2_subdev_get_try_* helpers to v4l2_subdev_get_pad_*, but due
> to the size of that change lets add temporary wrapper helpers which can
> be used in drivers that support active state.
> 
> Signed-off-by: Tomi Valkeinen <tomi.valkeinen@ideasonboard.com>

Reviewed-by: Hans Verkuil <hverkuil-cisco@xs4all.nl>

> ---
>  include/media/v4l2-subdev.h | 10 ++++++++++
>  1 file changed, 10 insertions(+)
> 
> diff --git a/include/media/v4l2-subdev.h b/include/media/v4l2-subdev.h
> index 1bbe4383966c..b9587a265b32 100644
> --- a/include/media/v4l2-subdev.h
> +++ b/include/media/v4l2-subdev.h
> @@ -1042,6 +1042,16 @@ v4l2_subdev_get_try_compose(struct v4l2_subdev *sd,
>  	return &state->pads[pad].try_compose;
>  }
>  
> +/* Temprary helpers until v4l2_subdev_get_try_* functions have been renamed */
> +#define v4l2_subdev_get_pad_format(sd, state, pad) \
> +	v4l2_subdev_get_try_format(sd, state, pad)
> +
> +#define v4l2_subdev_get_pad_crop(sd, state, pad) \
> +	v4l2_subdev_get_try_crop(sd, state, pad)
> +
> +#define v4l2_subdev_get_pad_compose(sd, state, pad) \
> +	v4l2_subdev_get_try_compose(sd, state, pad)
> +
>  #endif
>  
>  extern const struct v4l2_file_operations v4l2_subdev_fops;

Re: [PATCH v6 5/8] media: subdev: add subdev state locking

[Hans Verkuil]

On 24/03/2022 09:00, Tomi Valkeinen wrote:
> 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.
> 
> However, active-state locking is complicated by the fact that currently
> the real active-state of a subdev is split into multiple parts: the new
> v4l2_subdev_state, subdev control state, and subdev's internal state.
> 
> In the future all these three states should be combined into one state
> (the v4l2_subdev_state), and then a single lock for the state should be
> sufficient.
> 
> But to solve the current split-state situation we need to share locks
> between the three states. This is accomplished by using the same lock
> management as the control handler does: we use a pointer to a mutex,
> allowing the driver to override the default mutex. Thus the driver can
> do e.g.:
> 
> sd->state_lock = sd->ctrl_handler->lock;
> 
> before calling v4l2_subdev_init_finalize(), resulting in sharing the
> same lock between the states and the controls.
> 
> The locking model for active-state is such that any subdev op that gets
> the state as a parameter expects the state to be already locked by the
> caller, and expects the caller to release the lock.
> 
> Signed-off-by: Tomi Valkeinen <tomi.valkeinen@ideasonboard.com>
> Reviewed-by: Laurent Pinchart <laurent.pinchart@ideasonboard.com>

Reviewed-by: Hans Verkuil <hverkuil-cisco@xs4all.nl>

Regards,

	Hans

> ---
>  .../platform/renesas/rcar-vin/rcar-v4l2.c     |   3 +-
>  .../media/platform/renesas/vsp1/vsp1_entity.c |   4 +-
>  drivers/media/v4l2-core/v4l2-subdev.c         |  63 ++++++---
>  drivers/staging/media/tegra-video/vi.c        |   4 +-
>  include/media/v4l2-subdev.h                   | 133 +++++++++++++++++-
>  5 files changed, 181 insertions(+), 26 deletions(-)
> 
> diff --git a/drivers/media/platform/renesas/rcar-vin/rcar-v4l2.c b/drivers/media/platform/renesas/rcar-vin/rcar-v4l2.c
> index da88f968c31a..3759f4619a77 100644
> --- a/drivers/media/platform/renesas/rcar-vin/rcar-v4l2.c
> +++ b/drivers/media/platform/renesas/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,
> @@ -267,7 +268,7 @@ static int rvin_try_format(struct rvin_dev *vin, u32 which,
>  	 * FIXME: Drop this call, drivers are not supposed to use
>  	 * __v4l2_subdev_state_alloc().
>  	 */
> -	sd_state = __v4l2_subdev_state_alloc(sd);
> +	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/renesas/vsp1/vsp1_entity.c b/drivers/media/platform/renesas/vsp1/vsp1_entity.c
> index c82b3fb7b89a..a116a3362f9e 100644
> --- a/drivers/media/platform/renesas/vsp1/vsp1_entity.c
> +++ b/drivers/media/platform/renesas/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;
> @@ -679,7 +680,8 @@ int vsp1_entity_init(struct vsp1_device *vsp1, struct vsp1_entity *entity,
>  	 * FIXME: Drop this call, drivers are not supposed to use
>  	 * __v4l2_subdev_state_alloc().
>  	 */
> -	entity->config = __v4l2_subdev_state_alloc(&entity->subdev);
> +	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 b67bbce82612..824424f0a741 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);
>  
> @@ -380,21 +381,18 @@ subdev_ioctl_get_state(struct v4l2_subdev *sd, struct v4l2_subdev_fh *subdev_fh,
>  
>  	return which == V4L2_SUBDEV_FORMAT_TRY ?
>  			     subdev_fh->state :
> -			     v4l2_subdev_get_active_state(sd);
> +			     v4l2_subdev_get_unlocked_active_state(sd);
>  }
>  
> -static long subdev_do_ioctl(struct file *file, unsigned int cmd, void *arg)
> +static long subdev_do_ioctl(struct file *file, unsigned int cmd, void *arg,
> +			    struct v4l2_subdev_state *state)
>  {
>  	struct video_device *vdev = video_devdata(file);
>  	struct v4l2_subdev *sd = vdev_to_v4l2_subdev(vdev);
>  	struct v4l2_fh *vfh = file->private_data;
> -	struct v4l2_subdev_fh *subdev_fh = to_v4l2_subdev_fh(vfh);
>  	bool ro_subdev = test_bit(V4L2_FL_SUBDEV_RO_DEVNODE, &vdev->flags);
> -	struct v4l2_subdev_state *state;
>  	int rval;
>  
> -	state = subdev_ioctl_get_state(sd, subdev_fh, cmd, arg);
> -
>  	switch (cmd) {
>  	case VIDIOC_SUBDEV_QUERYCAP: {
>  		struct v4l2_subdev_capability *cap = arg;
> @@ -707,8 +705,24 @@ static long subdev_do_ioctl_lock(struct file *file, unsigned int cmd, void *arg)
>  
>  	if (lock && mutex_lock_interruptible(lock))
>  		return -ERESTARTSYS;
> -	if (video_is_registered(vdev))
> -		ret = subdev_do_ioctl(file, cmd, arg);
> +
> +	if (video_is_registered(vdev)) {
> +		struct v4l2_subdev *sd = vdev_to_v4l2_subdev(vdev);
> +		struct v4l2_fh *vfh = file->private_data;
> +		struct v4l2_subdev_fh *subdev_fh = to_v4l2_subdev_fh(vfh);
> +		struct v4l2_subdev_state *state;
> +
> +		state = subdev_ioctl_get_state(sd, subdev_fh, cmd, arg);
> +
> +		if (state)
> +			v4l2_subdev_lock_state(state);
> +
> +		ret = subdev_do_ioctl(file, cmd, arg, state);
> +
> +		if (state)
> +			v4l2_subdev_unlock_state(state);
> +	}
> +
>  	if (lock)
>  		mutex_unlock(lock);
>  	return ret;
> @@ -862,13 +876,10 @@ v4l2_subdev_link_validate_get_format(struct media_pad *pad,
>  	if (is_media_entity_v4l2_subdev(pad->entity)) {
>  		struct v4l2_subdev *sd =
>  			media_entity_to_v4l2_subdev(pad->entity);
> -		struct v4l2_subdev_state *state;
> -
> -		state = v4l2_subdev_get_active_state(sd);
>  
>  		fmt->which = V4L2_SUBDEV_FORMAT_ACTIVE;
>  		fmt->pad = pad->index;
> -		return v4l2_subdev_call(sd, pad, get_fmt, state, fmt);
> +		return v4l2_subdev_call_state_active(sd, pad, get_fmt, fmt);
>  	}
>  
>  	WARN(pad->entity->function != MEDIA_ENT_F_IO_V4L,
> @@ -906,7 +917,9 @@ 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;
> @@ -915,6 +928,12 @@ 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->state_lock)
> +		state->lock = sd->state_lock;
> +	else
> +		state->lock = &state->_lock;
> +
>  	if (sd->entity.num_pads) {
>  		state->pads = kvmalloc_array(sd->entity.num_pads,
>  					     sizeof(*state->pads),
> @@ -925,7 +944,14 @@ struct v4l2_subdev_state *__v4l2_subdev_state_alloc(struct v4l2_subdev *sd)
>  		}
>  	}
>  
> +	/*
> +	 * There can be no race at this point, but we lock the state anyway to
> +	 * satisfy lockdep checks.
> +	 */
> +	v4l2_subdev_lock_state(state);
>  	ret = v4l2_subdev_call(sd, pad, init_cfg, state);
> +	v4l2_subdev_unlock_state(state);
> +
>  	if (ret < 0 && ret != -ENOIOCTLCMD)
>  		goto err;
>  
> @@ -946,16 +972,19 @@ void __v4l2_subdev_state_free(struct v4l2_subdev_state *state)
>  	if (!state)
>  		return;
>  
> +	mutex_destroy(&state->_lock);
> +
>  	kvfree(state->pads);
>  	kfree(state);
>  }
>  EXPORT_SYMBOL_GPL(__v4l2_subdev_state_free);
>  
> -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);
>  
> @@ -963,7 +992,7 @@ 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)
>  {
> diff --git a/drivers/staging/media/tegra-video/vi.c b/drivers/staging/media/tegra-video/vi.c
> index 07d368f345cd..8e184aa4c252 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;
> @@ -511,7 +512,8 @@ static int __tegra_channel_try_format(struct tegra_vi_channel *chan,
>  	 * FIXME: Drop this call, drivers are not supposed to use
>  	 * __v4l2_subdev_state_alloc().
>  	 */
> -	sd_state = __v4l2_subdev_state_alloc(subdev);
> +	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 b9587a265b32..700ce376b22c 100644
> --- a/include/media/v4l2-subdev.h
> +++ b/include/media/v4l2-subdev.h
> @@ -658,6 +658,8 @@ struct v4l2_subdev_pad_config {
>  /**
>   * struct v4l2_subdev_state - Used for storing subdev state information.
>   *
> + * @_lock: default for 'lock'
> + * @lock: mutex for the state. May be replaced by the user.
>   * @pads: &struct v4l2_subdev_pad_config array
>   *
>   * This structure only needs to be passed to the pad op if the 'which' field
> @@ -665,6 +667,9 @@ 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 mutex *lock;
>  	struct v4l2_subdev_pad_config *pads;
>  };
>  
> @@ -888,6 +893,9 @@ struct v4l2_subdev_platform_data {
>   * @subdev_notifier: A sub-device notifier implicitly registered for the sub-
>   *		     device using v4l2_async_register_subdev_sensor().
>   * @pdata: common part of subdevice platform data
> + * @state_lock: A pointer to a lock used for all the subdev's states, set by the
> + *		driver. This is	optional. If NULL, each state instance will get
> + *		a lock of its own.
>   * @active_state: Active state for the subdev (NULL for subdevs tracking the
>   *		  state internally). Initialized by calling
>   *		  v4l2_subdev_init_finalize().
> @@ -922,6 +930,7 @@ struct v4l2_subdev {
>  	struct v4l2_async_notifier *notifier;
>  	struct v4l2_async_notifier *subdev_notifier;
>  	struct v4l2_subdev_platform_data *pdata;
> +	struct mutex *state_lock;
>  
>  	/*
>  	 * The fields below are private, and should only be accessed via
> @@ -1154,12 +1163,16 @@ 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.
>   *
>   * Not to be called directly by the drivers.
>   */
> -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
> @@ -1184,7 +1197,16 @@ void __v4l2_subdev_state_free(struct v4l2_subdev_state *state);
>   *
>   * 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__) ":sd->active_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 allocated by the subdevice
> @@ -1196,16 +1218,85 @@ int v4l2_subdev_init_finalize(struct v4l2_subdev *sd);
>  void v4l2_subdev_cleanup(struct v4l2_subdev *sd);
>  
>  /**
> - * v4l2_subdev_get_active_state() - Returns the active subdev state for
> - *				    subdevice
> + * 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.
> + */
> +static inline void v4l2_subdev_lock_state(struct v4l2_subdev_state *state)
> +{
> +	mutex_lock(state->lock);
> +}
> +
> +/**
> + * v4l2_subdev_unlock_state() - Unlocks the subdev state
> + * @state: The subdevice state
> + *
> + * Unlocks the given subdev state.
> + */
> +static inline void v4l2_subdev_unlock_state(struct v4l2_subdev_state *state)
> +{
> +	mutex_unlock(state->lock);
> +}
> +
> +/**
> + * v4l2_subdev_get_unlocked_active_state() - Checks that the active subdev state
> + *					     is unlocked and returns it
> + * @sd: The subdevice
> + *
> + * Returns the active state for the subdevice, or NULL if the subdev does not
> + * support active state. If the state is not NULL, calls
> + * lockdep_assert_not_held() to issue a warning if the state is locked.
> + *
> + * This function is to be used e.g. when getting the active state for the sole
> + * purpose of passing it forward, without accessing the state fields.
> + */
> +static inline struct v4l2_subdev_state *
> +v4l2_subdev_get_unlocked_active_state(struct v4l2_subdev *sd)
> +{
> +	if (sd->active_state)
> +		lockdep_assert_not_held(sd->active_state->lock);
> +	return sd->active_state;
> +}
> +
> +/**
> + * v4l2_subdev_get_locked_active_state() - Checks that the active subdev state
> + *					   is locked and returns it
> + *
>   * @sd: The subdevice
>   *
>   * Returns the active state for the subdevice, or NULL if the subdev does not
> - * support active state.
> + * support active state. If the state is not NULL, calls lockdep_assert_held()
> + * to issue a warning if the state is not locked.
> + *
> + * This function is to be used when the caller knows that the active state is
> + * already locked.
> + */
> +static inline struct v4l2_subdev_state *
> +v4l2_subdev_get_locked_active_state(struct v4l2_subdev *sd)
> +{
> +	if (sd->active_state)
> +		lockdep_assert_held(sd->active_state->lock);
> +	return sd->active_state;
> +}
> +
> +/**
> + * v4l2_subdev_lock_and_get_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.
>   */
>  static inline struct v4l2_subdev_state *
> -v4l2_subdev_get_active_state(struct v4l2_subdev *sd)
> +v4l2_subdev_lock_and_get_active_state(struct v4l2_subdev *sd)
>  {
> +	if (sd->active_state)
> +		v4l2_subdev_lock_state(sd->active_state);
>  	return sd->active_state;
>  }
>  
> @@ -1252,6 +1343,36 @@ extern const struct v4l2_subdev_ops v4l2_subdev_call_wrappers;
>  		__result;						\
>  	})
>  
> +/**
> + * v4l2_subdev_call_state_active - call an operation of a v4l2_subdev which
> + *				   takes state as a parameter, passing the
> + *				   subdev its active state.
> + *
> + * @sd: pointer to the &struct v4l2_subdev
> + * @o: name of the element at &struct v4l2_subdev_ops that contains @f.
> + *     Each element there groups a set of callbacks functions.
> + * @f: callback function to be called.
> + *     The callback functions are defined in groups, according to
> + *     each element at &struct v4l2_subdev_ops.
> + * @args: arguments for @f.
> + *
> + * This is similar to v4l2_subdev_call(), except that this version can only be
> + * used for ops that take a subdev state as a parameter. The macro will get the
> + * active state, lock it before calling the op and unlock it after the call.
> + */
> +#define v4l2_subdev_call_state_active(sd, o, f, args...)		\
> +	({								\
> +		int __result;						\
> +		struct v4l2_subdev_state *state;			\
> +		state = v4l2_subdev_get_unlocked_active_state(sd);	\
> +		if (state)						\
> +			v4l2_subdev_lock_state(state);			\
> +		__result = v4l2_subdev_call(sd, o, f, state, ##args);	\
> +		if (state)						\
> +			v4l2_subdev_unlock_state(state);		\
> +		__result;						\
> +	})
> +
>  /**
>   * v4l2_subdev_has_op - Checks if a subdev defines a certain operation.
>   *

Re: [PATCH v6 6/8] media: subdev: add locking wrappers to subdev op wrappers

[Hans Verkuil]

On 24/03/2022 09:00, Tomi Valkeinen wrote:
> It is common that media drivers call subdev ops in source subdevs, and
> pass NULL as the state. This was the way to indicate that the callee
> should use the callee's private active state.
> 
> E.g.:
> 
> v4l2_subdev_call(priv->source_sd, pad, get_fmt, NULL, &sd_fmt);
> 
> Now that we have a real subdev active state in the v4l2_subdev struct,
> we want the caller to pass a proper state (when available). And
> furthermore, the state should be locked.
> 
> This would mean changing all the callers, which is the long term goal.
> 
> To fix this issue in the short term, let's add an extra wrapper layer to
> all v4l2_subdev_call_pad_wrappers which deal with states. These wrappers
> handle the state == NULL case by using the locked active state instead
> (when available).
> 
> Signed-off-by: Tomi Valkeinen <tomi.valkeinen@ideasonboard.com>

Reviewed-by: Hans Verkuil <hverkuil-cisco@xs4all.nl>

Regards,

	Hans

> ---
>  drivers/media/v4l2-core/v4l2-subdev.c | 42 ++++++++++++++++++++++-----
>  1 file changed, 35 insertions(+), 7 deletions(-)
> 
> diff --git a/drivers/media/v4l2-core/v4l2-subdev.c b/drivers/media/v4l2-core/v4l2-subdev.c
> index 824424f0a741..d8d1c9ef4dc4 100644
> --- a/drivers/media/v4l2-core/v4l2-subdev.c
> +++ b/drivers/media/v4l2-core/v4l2-subdev.c
> @@ -319,14 +319,42 @@ static int call_get_mbus_config(struct v4l2_subdev *sd, unsigned int pad,
>  	       sd->ops->pad->get_mbus_config(sd, pad, config);
>  }
>  
> +/*
> + * Create state-management wrapper for pad ops dealing with subdev state. The
> + * wrapper handles the case where the caller does not provide the called
> + * subdev's state. This should be removed when all the callers are fixed.
> + */
> +#define DEFINE_STATE_WRAPPER(f, arg_type)                                  \
> +	static int call_##f##_state(struct v4l2_subdev *sd,                \
> +				    struct v4l2_subdev_state *_state,      \
> +				    arg_type *format)                      \
> +	{                                                                  \
> +		struct v4l2_subdev_state *state = _state;                  \
> +		int ret;                                                   \
> +		if (!_state)                                               \
> +			state = v4l2_subdev_lock_and_get_active_state(sd); \
> +		ret = call_##f(sd, state, format);                         \
> +		if (!_state && state)                                      \
> +			v4l2_subdev_unlock_state(state);                   \
> +		return ret;                                                \
> +	}
> +
> +DEFINE_STATE_WRAPPER(get_fmt, struct v4l2_subdev_format);
> +DEFINE_STATE_WRAPPER(set_fmt, struct v4l2_subdev_format);
> +DEFINE_STATE_WRAPPER(enum_mbus_code, struct v4l2_subdev_mbus_code_enum);
> +DEFINE_STATE_WRAPPER(enum_frame_size, struct v4l2_subdev_frame_size_enum);
> +DEFINE_STATE_WRAPPER(enum_frame_interval, struct v4l2_subdev_frame_interval_enum);
> +DEFINE_STATE_WRAPPER(get_selection, struct v4l2_subdev_selection);
> +DEFINE_STATE_WRAPPER(set_selection, struct v4l2_subdev_selection);
> +
>  static const struct v4l2_subdev_pad_ops v4l2_subdev_call_pad_wrappers = {
> -	.get_fmt		= call_get_fmt,
> -	.set_fmt		= call_set_fmt,
> -	.enum_mbus_code		= call_enum_mbus_code,
> -	.enum_frame_size	= call_enum_frame_size,
> -	.enum_frame_interval	= call_enum_frame_interval,
> -	.get_selection		= call_get_selection,
> -	.set_selection		= call_set_selection,
> +	.get_fmt		= call_get_fmt_state,
> +	.set_fmt		= call_set_fmt_state,
> +	.enum_mbus_code		= call_enum_mbus_code_state,
> +	.enum_frame_size	= call_enum_frame_size_state,
> +	.enum_frame_interval	= call_enum_frame_interval_state,
> +	.get_selection		= call_get_selection_state,
> +	.set_selection		= call_set_selection_state,
>  	.get_edid		= call_get_edid,
>  	.set_edid		= call_set_edid,
>  	.dv_timings_cap		= call_dv_timings_cap,

Re: [PATCH v6 7/8] media: subdev: add v4l2_subdev_get_fmt() helper function

[Hans Verkuil]

On 24/03/2022 09:00, Tomi Valkeinen wrote:
> Add v4l2_subdev_get_fmt() helper function which implements
> v4l2_subdev_pad_ops.get_fmt using active state. Subdev drivers that
> support active state and do not need to do anything special in their
> get_fmt op can use this helper directly for v4l2_subdev_pad_ops.get_fmt.
> 
> Signed-off-by: Tomi Valkeinen <tomi.valkeinen@ideasonboard.com>
> ---
>  drivers/media/v4l2-core/v4l2-subdev.c | 18 ++++++++++++++++++
>  include/media/v4l2-subdev.h           | 17 +++++++++++++++++
>  2 files changed, 35 insertions(+)
> 
> diff --git a/drivers/media/v4l2-core/v4l2-subdev.c b/drivers/media/v4l2-core/v4l2-subdev.c
> index d8d1c9ef4dc4..cbc5ebff0656 100644
> --- a/drivers/media/v4l2-core/v4l2-subdev.c
> +++ b/drivers/media/v4l2-core/v4l2-subdev.c
> @@ -1029,6 +1029,24 @@ void v4l2_subdev_cleanup(struct v4l2_subdev *sd)
>  }
>  EXPORT_SYMBOL_GPL(v4l2_subdev_cleanup);
>  
> +int v4l2_subdev_get_fmt(struct v4l2_subdev *sd, struct v4l2_subdev_state *state,
> +			struct v4l2_subdev_format *format)
> +{
> +	struct v4l2_mbus_framefmt *fmt;
> +
> +	if (format->pad >= sd->entity.num_pads)
> +		return -EINVAL;
> +
> +	fmt = v4l2_subdev_get_try_format(sd, state, format->pad);

Let's use the new v4l2_subdev_get_pad_format helper here.

> +	if (!fmt)
> +		return -EINVAL;
> +
> +	format->format = *fmt;
> +
> +	return 0;
> +}
> +EXPORT_SYMBOL_GPL(v4l2_subdev_get_fmt);
> +
>  #endif /* CONFIG_MEDIA_CONTROLLER */
>  
>  void v4l2_subdev_init(struct v4l2_subdev *sd, const struct v4l2_subdev_ops *ops)
> diff --git a/include/media/v4l2-subdev.h b/include/media/v4l2-subdev.h
> index 700ce376b22c..491bdbb1670c 100644
> --- a/include/media/v4l2-subdev.h
> +++ b/include/media/v4l2-subdev.h
> @@ -1300,6 +1300,23 @@ v4l2_subdev_lock_and_get_active_state(struct v4l2_subdev *sd)
>  	return sd->active_state;
>  }
>  
> +/**
> + * v4l2_subdev_get_fmt() - Fill format based on state
> + * @sd: subdevice
> + * @state: subdevice state
> + * @format: pointer to &struct v4l2_subdev_format
> + *
> + * Fill @format->format field based on the information in the @format struct.
> + *
> + * This function can be used by the subdev drivers which support active state to
> + * implement v4l2_subdev_pad_ops.get_fmt if the subdev driver does not need to
> + * do anything special in their get_fmt op.
> + *
> + * Returns 0 on success, error value otherwise.
> + */
> +int v4l2_subdev_get_fmt(struct v4l2_subdev *sd, struct v4l2_subdev_state *state,
> +			struct v4l2_subdev_format *format);

My main concern here is the function name: perhaps a prefix like
v4l2_subdev_pad_op_get_fmt (or perhaps just _op_ without 'pad') makes
it easier to see that this is a pad op helper.

In any case, this is not a blocker. With the v4l2_subdev_get_pad_format
above and an optional function rename you can add my:

Reviewed-by: Hans Verkuil <hverkuil-cisco@xs4all.nl>

Regards,

	Hans


> +
>  #endif /* CONFIG_MEDIA_CONTROLLER */
>  
>  /**

Re: [PATCH v6 3/8] media: subdev: add v4l2_subdev_get_pad_* helpers

[Hans Verkuil]

On 06/04/2022 15:36, Hans Verkuil wrote:
> 
> 
> On 24/03/2022 09:00, Tomi Valkeinen wrote:
>> The subdev state is now used for both try and active cases. We should
>> rename v4l2_subdev_get_try_* helpers to v4l2_subdev_get_pad_*, but due
>> to the size of that change lets add temporary wrapper helpers which can
>> be used in drivers that support active state.
>>
>> Signed-off-by: Tomi Valkeinen <tomi.valkeinen@ideasonboard.com>
> 
> Reviewed-by: Hans Verkuil <hverkuil-cisco@xs4all.nl>
> 
>> ---
>>  include/media/v4l2-subdev.h | 10 ++++++++++
>>  1 file changed, 10 insertions(+)
>>
>> diff --git a/include/media/v4l2-subdev.h b/include/media/v4l2-subdev.h
>> index 1bbe4383966c..b9587a265b32 100644
>> --- a/include/media/v4l2-subdev.h
>> +++ b/include/media/v4l2-subdev.h
>> @@ -1042,6 +1042,16 @@ v4l2_subdev_get_try_compose(struct v4l2_subdev *sd,
>>  	return &state->pads[pad].try_compose;
>>  }
>>  
>> +/* Temprary helpers until v4l2_subdev_get_try_* functions have been renamed */
>> +#define v4l2_subdev_get_pad_format(sd, state, pad) \
>> +	v4l2_subdev_get_try_format(sd, state, pad)
>> +
>> +#define v4l2_subdev_get_pad_crop(sd, state, pad) \
>> +	v4l2_subdev_get_try_crop(sd, state, pad)
>> +
>> +#define v4l2_subdev_get_pad_compose(sd, state, pad) \
>> +	v4l2_subdev_get_try_compose(sd, state, pad)

Actually, wouldn't it be better to rename the try helpers and
add #defines for the old names?

I think I prefer that.

Regards,

	Hans

>> +
>>  #endif
>>  
>>  extern const struct v4l2_file_operations v4l2_subdev_fops;

Re: [PATCH v6 8/8] media: Documentation: add documentation about subdev state

[Hans Verkuil]

On 24/03/2022 09:00, Tomi Valkeinen wrote:
> Add documentation about centrally managed subdev state.
> 
> Signed-off-by: Tomi Valkeinen <tomi.valkeinen@ideasonboard.com>
> Reviewed-by: Jacopo Mondi <jacopo+renesas@jmondi.org>
> Reviewed-by: Hans Verkuil <hverkuil-cisco@xs4all.nl>
> Reviewed-by: Laurent Pinchart <laurent.pinchart@ideasonboard.com>
> ---
>  .../driver-api/media/v4l2-subdev.rst          | 75 +++++++++++++++++++
>  1 file changed, 75 insertions(+)
> 
> diff --git a/Documentation/driver-api/media/v4l2-subdev.rst b/Documentation/driver-api/media/v4l2-subdev.rst
> index 08ea2673b19e..7fa950b1bff0 100644
> --- a/Documentation/driver-api/media/v4l2-subdev.rst
> +++ b/Documentation/driver-api/media/v4l2-subdev.rst
> @@ -518,6 +518,81 @@ The :c:func:`v4l2_i2c_new_subdev` function will call
>  :c:type:`i2c_board_info` structure using the ``client_type`` and the
>  ``addr`` to fill it.
>  
> +Centrally managed subdev active state
> +-------------------------------------
> +
> +Traditionally V4L2 subdev drivers maintained internal state for the active
> +device configuration. This is often implemented as e.g. an array of struct
> +v4l2_mbus_framefmt, one entry for each pad, and similarly for crop and compose
> +rectangles.
> +
> +In addition to the active configuration, each subdev file handle has an array of
> +struct v4l2_subdev_pad_config, managed by the V4L2 core, which contains the try
> +configuration.
> +
> +To simplify the subdev drivers the V4L2 subdev API now optionally supports a
> +centrally managed active configuration represented by
> +:c:type:`v4l2_subdev_state`. One instance of state, which contains the active
> +device configuration, is stored in the sub-device itself as part of
> +the :c:type:`v4l2_subdev` structure, while the core associates a try state to
> +each open file handle, to store the try configuration related to that file
> +handle.
> +
> +Sub-device drivers can opt-in and use state to manage their active configuration
> +by initializing the subdevice state with a call to v4l2_subdev_init_finalize()
> +before registering the sub-device. They must also call v4l2_subdev_cleanup()
> +to release all the allocated resources before unregistering the sub-device.
> +The core automatically allocates and initializes a state for each open file
> +handle to store the try configurations and frees it when closing the file
> +handle.
> +
> +V4L2 sub-device operations that use both the :ref:`ACTIVE and TRY formats
> +<v4l2-subdev-format-whence>` receive the correct state to operate on through
> +the 'state' parameter. The state must be locked and unlocked by the
> +caller by calling :c:func:`v4l2_subdev_lock_state()` and
> +:c:func:`v4l2_subdev_unlock_state()`. The caller can do so by calling the subdev
> +operation through the :c:func:`v4l2_subdev_call_state_active()` macro.
> +
> +Operations that do not receive a state parameter implicitly operate on the
> +subdevice active state, which drivers can exclusively access by
> +calling :c:func:`v4l2_subdev_lock_and_get_active_state()`. The sub-device active
> +state must equally be released by calling :c:func:`v4l2_subdev_unlock_state()`.
> +
> +Drivers must never manually access the state stored in the :c:type:`v4l2_subdev`
> +or in the file handle without going through the designated helpers.
> +
> +While the V4L2 core passes the correct try or active state to the
> +subdevice operations, some existing device drivers pass a NULL state
> +when calling operations with :c:func:`v4l2_subdev_call()`. This legacy
> +construct causes issues with subdevice drivers that let the V4L2 core
> +manage the active state, as they expect to receive the appropriate state
> +as a parameter. To help the conversion of subdevice drivers to a managed
> +active state without having to convert all callers at the same time, the
> +:c:func:`v4l2_subdev_lock_and_return_state()` helper function can be

This is an old name, right? It's no longer called v4l2_subdev_lock_and_return_state.
Note that the commit log of patch 4 also refers to this old name.

Actually, isn't this now replaced by the subdev op wrappers? (I might be wrong,
I don't have much time to review this patch).

> +used by subdevice drivers to retrieve the active state if a NULL state
> +is passed to the subdevice operation.
> +
> +:c:func:`v4l2_subdev_lock_and_return_state()` should only be used when porting
> +an existing driver to the new state management when it cannot be guaranteed
> +that the current callers will pass the state properly. The function prints a
> +notice when the passed state is NULL to encourage the porting of the callers
> +to the new state management.
> +
> +The whole subdev state is in reality split into three parts: the
> +v4l2_subdev_state, subdev controls and subdev driver's internal state. In the
> +future these parts should be combined into a single state. For the time being
> +we need a way to handle the locking for these parts. This can be accomplished
> +by sharing a lock. The v4l2_ctrl_handler already supports this via its 'lock'
> +pointer and the same model is used with states. The driver can do the following
> +before calling v4l2_subdev_init_finalize():
> +
> +.. code-block:: c
> +
> +	sd->ctrl_handler->lock = &priv->mutex;
> +	sd->state_lock = &priv->mutex;
> +
> +This shares the driver's private mutex between the controls and the states.
> +
>  V4L2 sub-device functions and data structures
>  ---------------------------------------------
>  

Regards,

	Hans

Re: [PATCH v6 3/8] media: subdev: add v4l2_subdev_get_pad_* helpers

[Tomi Valkeinen]

On 06/04/2022 16:52, Hans Verkuil wrote:
> 
> 
> On 06/04/2022 15:36, Hans Verkuil wrote:
>>
>>
>> On 24/03/2022 09:00, Tomi Valkeinen wrote:
>>> The subdev state is now used for both try and active cases. We should
>>> rename v4l2_subdev_get_try_* helpers to v4l2_subdev_get_pad_*, but due
>>> to the size of that change lets add temporary wrapper helpers which can
>>> be used in drivers that support active state.
>>>
>>> Signed-off-by: Tomi Valkeinen <tomi.valkeinen@ideasonboard.com>
>>
>> Reviewed-by: Hans Verkuil <hverkuil-cisco@xs4all.nl>
>>
>>> ---
>>>   include/media/v4l2-subdev.h | 10 ++++++++++
>>>   1 file changed, 10 insertions(+)
>>>
>>> diff --git a/include/media/v4l2-subdev.h b/include/media/v4l2-subdev.h
>>> index 1bbe4383966c..b9587a265b32 100644
>>> --- a/include/media/v4l2-subdev.h
>>> +++ b/include/media/v4l2-subdev.h
>>> @@ -1042,6 +1042,16 @@ v4l2_subdev_get_try_compose(struct v4l2_subdev *sd,
>>>   	return &state->pads[pad].try_compose;
>>>   }
>>>   
>>> +/* Temprary helpers until v4l2_subdev_get_try_* functions have been renamed */
>>> +#define v4l2_subdev_get_pad_format(sd, state, pad) \
>>> +	v4l2_subdev_get_try_format(sd, state, pad)
>>> +
>>> +#define v4l2_subdev_get_pad_crop(sd, state, pad) \
>>> +	v4l2_subdev_get_try_crop(sd, state, pad)
>>> +
>>> +#define v4l2_subdev_get_pad_compose(sd, state, pad) \
>>> +	v4l2_subdev_get_try_compose(sd, state, pad)
> 
> Actually, wouldn't it be better to rename the try helpers and
> add #defines for the old names?
> 
> I think I prefer that.

Yes, that's a good idea.

  Tomi

Re: [PATCH v6 7/8] media: subdev: add v4l2_subdev_get_fmt() helper function

[Tomi Valkeinen]

On 06/04/2022 16:51, Hans Verkuil wrote:
> 
> 
> On 24/03/2022 09:00, Tomi Valkeinen wrote:
>> Add v4l2_subdev_get_fmt() helper function which implements
>> v4l2_subdev_pad_ops.get_fmt using active state. Subdev drivers that
>> support active state and do not need to do anything special in their
>> get_fmt op can use this helper directly for v4l2_subdev_pad_ops.get_fmt.
>>
>> Signed-off-by: Tomi Valkeinen <tomi.valkeinen@ideasonboard.com>
>> ---
>>   drivers/media/v4l2-core/v4l2-subdev.c | 18 ++++++++++++++++++
>>   include/media/v4l2-subdev.h           | 17 +++++++++++++++++
>>   2 files changed, 35 insertions(+)
>>
>> diff --git a/drivers/media/v4l2-core/v4l2-subdev.c b/drivers/media/v4l2-core/v4l2-subdev.c
>> index d8d1c9ef4dc4..cbc5ebff0656 100644
>> --- a/drivers/media/v4l2-core/v4l2-subdev.c
>> +++ b/drivers/media/v4l2-core/v4l2-subdev.c
>> @@ -1029,6 +1029,24 @@ void v4l2_subdev_cleanup(struct v4l2_subdev *sd)
>>   }
>>   EXPORT_SYMBOL_GPL(v4l2_subdev_cleanup);
>>   
>> +int v4l2_subdev_get_fmt(struct v4l2_subdev *sd, struct v4l2_subdev_state *state,
>> +			struct v4l2_subdev_format *format)
>> +{
>> +	struct v4l2_mbus_framefmt *fmt;
>> +
>> +	if (format->pad >= sd->entity.num_pads)
>> +		return -EINVAL;
>> +
>> +	fmt = v4l2_subdev_get_try_format(sd, state, format->pad);
> 
> Let's use the new v4l2_subdev_get_pad_format helper here.

Right.

>> +	if (!fmt)
>> +		return -EINVAL;
>> +
>> +	format->format = *fmt;
>> +
>> +	return 0;
>> +}
>> +EXPORT_SYMBOL_GPL(v4l2_subdev_get_fmt);
>> +
>>   #endif /* CONFIG_MEDIA_CONTROLLER */
>>   
>>   void v4l2_subdev_init(struct v4l2_subdev *sd, const struct v4l2_subdev_ops *ops)
>> diff --git a/include/media/v4l2-subdev.h b/include/media/v4l2-subdev.h
>> index 700ce376b22c..491bdbb1670c 100644
>> --- a/include/media/v4l2-subdev.h
>> +++ b/include/media/v4l2-subdev.h
>> @@ -1300,6 +1300,23 @@ v4l2_subdev_lock_and_get_active_state(struct v4l2_subdev *sd)
>>   	return sd->active_state;
>>   }
>>   
>> +/**
>> + * v4l2_subdev_get_fmt() - Fill format based on state
>> + * @sd: subdevice
>> + * @state: subdevice state
>> + * @format: pointer to &struct v4l2_subdev_format
>> + *
>> + * Fill @format->format field based on the information in the @format struct.
>> + *
>> + * This function can be used by the subdev drivers which support active state to
>> + * implement v4l2_subdev_pad_ops.get_fmt if the subdev driver does not need to
>> + * do anything special in their get_fmt op.
>> + *
>> + * Returns 0 on success, error value otherwise.
>> + */
>> +int v4l2_subdev_get_fmt(struct v4l2_subdev *sd, struct v4l2_subdev_state *state,
>> +			struct v4l2_subdev_format *format);
> 
> My main concern here is the function name: perhaps a prefix like
> v4l2_subdev_pad_op_get_fmt (or perhaps just _op_ without 'pad') makes
> it easier to see that this is a pad op helper.

The function can and will be used also in other places. E.g. driver's 
set_fmt may use it to allow only setting the sink pad:

if (format->pad == MY_SOURCE_PAD)
	return v4l2_subdev_get_fmt(sd, state, format);

That's perhaps the only other use for the function, as it takes struct 
v4l2_subdev_format as a parameter, and I think usually that struct is 
only used with the set_fmt/get_fmt pad ops.

So, I guess "v4l2_subdev_pad_op_get_fmt" is suitable even in the example 
use case above. Then again, we do have other similar helper funcs 
without any extra prefixes, e.g. media_entity_operations:

	.get_fwnode_pad = v4l2_subdev_get_fwnode_pad_1_to_1,
	.link_validate = v4l2_subdev_link_validate,
	.has_route = v4l2_subdev_has_route

  Tomi

Re: [PATCH v6 7/8] media: subdev: add v4l2_subdev_get_fmt() helper function

[Hans Verkuil]

On 07/04/2022 09:23, Tomi Valkeinen wrote:
> On 06/04/2022 16:51, Hans Verkuil wrote:
>>
>>
>> On 24/03/2022 09:00, Tomi Valkeinen wrote:
>>> Add v4l2_subdev_get_fmt() helper function which implements
>>> v4l2_subdev_pad_ops.get_fmt using active state. Subdev drivers that
>>> support active state and do not need to do anything special in their
>>> get_fmt op can use this helper directly for v4l2_subdev_pad_ops.get_fmt.
>>>
>>> Signed-off-by: Tomi Valkeinen <tomi.valkeinen@ideasonboard.com>
>>> ---
>>>   drivers/media/v4l2-core/v4l2-subdev.c | 18 ++++++++++++++++++
>>>   include/media/v4l2-subdev.h           | 17 +++++++++++++++++
>>>   2 files changed, 35 insertions(+)
>>>
>>> diff --git a/drivers/media/v4l2-core/v4l2-subdev.c b/drivers/media/v4l2-core/v4l2-subdev.c
>>> index d8d1c9ef4dc4..cbc5ebff0656 100644
>>> --- a/drivers/media/v4l2-core/v4l2-subdev.c
>>> +++ b/drivers/media/v4l2-core/v4l2-subdev.c
>>> @@ -1029,6 +1029,24 @@ void v4l2_subdev_cleanup(struct v4l2_subdev *sd)
>>>   }
>>>   EXPORT_SYMBOL_GPL(v4l2_subdev_cleanup);
>>>   +int v4l2_subdev_get_fmt(struct v4l2_subdev *sd, struct v4l2_subdev_state *state,
>>> +            struct v4l2_subdev_format *format)
>>> +{
>>> +    struct v4l2_mbus_framefmt *fmt;
>>> +
>>> +    if (format->pad >= sd->entity.num_pads)
>>> +        return -EINVAL;
>>> +
>>> +    fmt = v4l2_subdev_get_try_format(sd, state, format->pad);
>>
>> Let's use the new v4l2_subdev_get_pad_format helper here.
> 
> Right.
> 
>>> +    if (!fmt)
>>> +        return -EINVAL;
>>> +
>>> +    format->format = *fmt;
>>> +
>>> +    return 0;
>>> +}
>>> +EXPORT_SYMBOL_GPL(v4l2_subdev_get_fmt);
>>> +
>>>   #endif /* CONFIG_MEDIA_CONTROLLER */
>>>     void v4l2_subdev_init(struct v4l2_subdev *sd, const struct v4l2_subdev_ops *ops)
>>> diff --git a/include/media/v4l2-subdev.h b/include/media/v4l2-subdev.h
>>> index 700ce376b22c..491bdbb1670c 100644
>>> --- a/include/media/v4l2-subdev.h
>>> +++ b/include/media/v4l2-subdev.h
>>> @@ -1300,6 +1300,23 @@ v4l2_subdev_lock_and_get_active_state(struct v4l2_subdev *sd)
>>>       return sd->active_state;
>>>   }
>>>   +/**
>>> + * v4l2_subdev_get_fmt() - Fill format based on state
>>> + * @sd: subdevice
>>> + * @state: subdevice state
>>> + * @format: pointer to &struct v4l2_subdev_format
>>> + *
>>> + * Fill @format->format field based on the information in the @format struct.
>>> + *
>>> + * This function can be used by the subdev drivers which support active state to
>>> + * implement v4l2_subdev_pad_ops.get_fmt if the subdev driver does not need to
>>> + * do anything special in their get_fmt op.
>>> + *
>>> + * Returns 0 on success, error value otherwise.
>>> + */
>>> +int v4l2_subdev_get_fmt(struct v4l2_subdev *sd, struct v4l2_subdev_state *state,
>>> +            struct v4l2_subdev_format *format);
>>
>> My main concern here is the function name: perhaps a prefix like
>> v4l2_subdev_pad_op_get_fmt (or perhaps just _op_ without 'pad') makes
>> it easier to see that this is a pad op helper.
> 
> The function can and will be used also in other places. E.g. driver's set_fmt may use it to allow only setting the sink pad:
> 
> if (format->pad == MY_SOURCE_PAD)
>     return v4l2_subdev_get_fmt(sd, state, format);
> 
> That's perhaps the only other use for the function, as it takes struct v4l2_subdev_format as a parameter, and I think usually that struct is only used with the set_fmt/get_fmt pad ops.
> 
> So, I guess "v4l2_subdev_pad_op_get_fmt" is suitable even in the example use case above. Then again, we do have other similar helper funcs without any extra prefixes, e.g. media_entity_operations:
> 
>     .get_fwnode_pad = v4l2_subdev_get_fwnode_pad_1_to_1,
>     .link_validate = v4l2_subdev_link_validate,
>     .has_route = v4l2_subdev_has_route

I personally think those should be renamed as well. But it is no big deal either.

If a helper is specifically meant to be used as an op function, then it should
be reflected in the name IMHO. If it can be used elsewhere as well, then it
becomes a gray area. In this particular case I am fine either way.

Regards,

	Hans

> 
>  Tomi

Re: [PATCH v6 8/8] media: Documentation: add documentation about subdev state

[Tomi Valkeinen]

On 06/04/2022 17:01, Hans Verkuil wrote:
> 
> 
> On 24/03/2022 09:00, Tomi Valkeinen wrote:
>> Add documentation about centrally managed subdev state.
>>
>> Signed-off-by: Tomi Valkeinen <tomi.valkeinen@ideasonboard.com>
>> Reviewed-by: Jacopo Mondi <jacopo+renesas@jmondi.org>
>> Reviewed-by: Hans Verkuil <hverkuil-cisco@xs4all.nl>
>> Reviewed-by: Laurent Pinchart <laurent.pinchart@ideasonboard.com>
>> ---
>>   .../driver-api/media/v4l2-subdev.rst          | 75 +++++++++++++++++++
>>   1 file changed, 75 insertions(+)
>>
>> diff --git a/Documentation/driver-api/media/v4l2-subdev.rst b/Documentation/driver-api/media/v4l2-subdev.rst
>> index 08ea2673b19e..7fa950b1bff0 100644
>> --- a/Documentation/driver-api/media/v4l2-subdev.rst
>> +++ b/Documentation/driver-api/media/v4l2-subdev.rst
>> @@ -518,6 +518,81 @@ The :c:func:`v4l2_i2c_new_subdev` function will call
>>   :c:type:`i2c_board_info` structure using the ``client_type`` and the
>>   ``addr`` to fill it.
>>   
>> +Centrally managed subdev active state
>> +-------------------------------------
>> +
>> +Traditionally V4L2 subdev drivers maintained internal state for the active
>> +device configuration. This is often implemented as e.g. an array of struct
>> +v4l2_mbus_framefmt, one entry for each pad, and similarly for crop and compose
>> +rectangles.
>> +
>> +In addition to the active configuration, each subdev file handle has an array of
>> +struct v4l2_subdev_pad_config, managed by the V4L2 core, which contains the try
>> +configuration.
>> +
>> +To simplify the subdev drivers the V4L2 subdev API now optionally supports a
>> +centrally managed active configuration represented by
>> +:c:type:`v4l2_subdev_state`. One instance of state, which contains the active
>> +device configuration, is stored in the sub-device itself as part of
>> +the :c:type:`v4l2_subdev` structure, while the core associates a try state to
>> +each open file handle, to store the try configuration related to that file
>> +handle.
>> +
>> +Sub-device drivers can opt-in and use state to manage their active configuration
>> +by initializing the subdevice state with a call to v4l2_subdev_init_finalize()
>> +before registering the sub-device. They must also call v4l2_subdev_cleanup()
>> +to release all the allocated resources before unregistering the sub-device.
>> +The core automatically allocates and initializes a state for each open file
>> +handle to store the try configurations and frees it when closing the file
>> +handle.
>> +
>> +V4L2 sub-device operations that use both the :ref:`ACTIVE and TRY formats
>> +<v4l2-subdev-format-whence>` receive the correct state to operate on through
>> +the 'state' parameter. The state must be locked and unlocked by the
>> +caller by calling :c:func:`v4l2_subdev_lock_state()` and
>> +:c:func:`v4l2_subdev_unlock_state()`. The caller can do so by calling the subdev
>> +operation through the :c:func:`v4l2_subdev_call_state_active()` macro.
>> +
>> +Operations that do not receive a state parameter implicitly operate on the
>> +subdevice active state, which drivers can exclusively access by
>> +calling :c:func:`v4l2_subdev_lock_and_get_active_state()`. The sub-device active
>> +state must equally be released by calling :c:func:`v4l2_subdev_unlock_state()`.
>> +
>> +Drivers must never manually access the state stored in the :c:type:`v4l2_subdev`
>> +or in the file handle without going through the designated helpers.
>> +
>> +While the V4L2 core passes the correct try or active state to the
>> +subdevice operations, some existing device drivers pass a NULL state
>> +when calling operations with :c:func:`v4l2_subdev_call()`. This legacy
>> +construct causes issues with subdevice drivers that let the V4L2 core
>> +manage the active state, as they expect to receive the appropriate state
>> +as a parameter. To help the conversion of subdevice drivers to a managed
>> +active state without having to convert all callers at the same time, the
>> +:c:func:`v4l2_subdev_lock_and_return_state()` helper function can be
> 
> This is an old name, right? It's no longer called v4l2_subdev_lock_and_return_state.
> Note that the commit log of patch 4 also refers to this old name.
> 
> Actually, isn't this now replaced by the subdev op wrappers? (I might be wrong,
> I don't have much time to review this patch).

That's correct, good catch. I have removed the parts about the drivers 
having to use v4l2_subdev_lock_and_get_active_state, and instead mention 
the additional call wrappers that automate this:

> To help the
> conversion of subdevice drivers to a managed active state without having to
> convert all callers at the same time, an additional wrapper layer has been
> added to v4l2_subdev_call(), which handles the NULL case by getting and locking
> the callee's active state with :c:func:`v4l2_subdev_lock_and_get_active_state()`,
> and unlocking the state after the call.

  Tomi