[PATCH 0/6] v4l: subdev active state

[PATCH 0/6] v4l: subdev active state

[Tomi Valkeinen]

Hi,

These are the first 6 patches from the "[PATCH v10 00/38] v4l: subdev
internal routing and streams" series. I'm posting these as a separate
series, as the active state patches are a separate topic from the
multiplexed streams.

There are changes in these patches compared to the v10 series in the
docs and comments. The only functional change is in the
v4l2_subdev_lock_and_return_state() function, where we now:

	if (!state)
		dev_notice_once(sd->dev, "source subdev should be ported to new state management\n");

I don't particularly like the text there, so if anyone has better
suggestions...

 Tomi

Tomi Valkeinen (6):
  media: subdev: rename subdev-state alloc & free
  media: subdev: add active state to struct v4l2_subdev
  media: subdev: pass also the active state to subdevs from ioctls
  media: subdev: add subdev state locking
  media: subdev: Add v4l2_subdev_lock_and_return_state()
  media: Documentation: add documentation about subdev state

 .../driver-api/media/v4l2-subdev.rst          |  58 +++++++
 drivers/media/platform/rcar-vin/rcar-v4l2.c   |   9 +-
 drivers/media/platform/vsp1/vsp1_entity.c     |  10 +-
 drivers/media/v4l2-core/v4l2-subdev.c         | 125 +++++++++++++--
 drivers/staging/media/tegra-video/vi.c        |  10 +-
 include/media/v4l2-subdev.h                   | 149 +++++++++++++++++-
 6 files changed, 334 insertions(+), 27 deletions(-)

-- 
2.25.1

[PATCH 1/6] 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>
---
 drivers/media/platform/rcar-vin/rcar-v4l2.c |  4 ++--
 drivers/media/platform/vsp1/vsp1_entity.c   |  4 ++--
 drivers/media/v4l2-core/v4l2-subdev.c       | 12 ++++++------
 drivers/staging/media/tegra-video/vi.c      |  4 ++--
 include/media/v4l2-subdev.h                 | 10 +++++-----
 5 files changed, 17 insertions(+), 17 deletions(-)

diff --git a/drivers/media/platform/rcar-vin/rcar-v4l2.c b/drivers/media/platform/rcar-vin/rcar-v4l2.c
index 2e60b9fce03b..5aae01456c04 100644
--- a/drivers/media/platform/rcar-vin/rcar-v4l2.c
+++ b/drivers/media/platform/rcar-vin/rcar-v4l2.c
@@ -263,7 +263,7 @@ static int rvin_try_format(struct rvin_dev *vin, u32 which,
 	u32 width, height;
 	int ret;
 
-	sd_state = v4l2_subdev_alloc_state(sd);
+	sd_state = __v4l2_subdev_state_alloc(sd);
 	if (IS_ERR(sd_state))
 		return PTR_ERR(sd_state);
 
@@ -299,7 +299,7 @@ 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/vsp1/vsp1_entity.c b/drivers/media/platform/vsp1/vsp1_entity.c
index 823c15facd1b..869cadc1468d 100644
--- a/drivers/media/platform/vsp1/vsp1_entity.c
+++ b/drivers/media/platform/vsp1/vsp1_entity.c
@@ -675,7 +675,7 @@ 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);
+	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 +690,6 @@ 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 5d27a27cc2f2..fe49c86a9b02 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;
 }
 
@@ -870,7 +870,7 @@ 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;
@@ -903,9 +903,9 @@ 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;
@@ -913,7 +913,7 @@ 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 69d9787d5338..b01f19e0f332 100644
--- a/drivers/staging/media/tegra-video/vi.c
+++ b/drivers/staging/media/tegra-video/vi.c
@@ -507,7 +507,7 @@ static int __tegra_channel_try_format(struct tegra_vi_channel *chan,
 	if (!subdev)
 		return -ENODEV;
 
-	sd_state = v4l2_subdev_alloc_state(subdev);
+	sd_state = __v4l2_subdev_state_alloc(subdev);
 	if (IS_ERR(sd_state))
 		return PTR_ERR(sd_state);
 	/*
@@ -558,7 +558,7 @@ 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 95ec18c2f49c..e52bf508c75b 100644
--- a/include/media/v4l2-subdev.h
+++ b/include/media/v4l2-subdev.h
@@ -1135,20 +1135,20 @@ 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.
  */
-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.
  */
-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 2/6] 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>
---
 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 fe49c86a9b02..de160140d63b 100644
--- a/drivers/media/v4l2-core/v4l2-subdev.c
+++ b/drivers/media/v4l2-core/v4l2-subdev.c
@@ -943,3 +943,24 @@ void v4l2_subdev_notify_event(struct v4l2_subdev *sd,
 	v4l2_subdev_notify(sd, V4L2_DEVICE_NOTIFY_EVENT, (void *)ev);
 }
 EXPORT_SYMBOL_GPL(v4l2_subdev_notify_event);
+
+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);
diff --git a/include/media/v4l2-subdev.h b/include/media/v4l2-subdev.h
index e52bf508c75b..eddf72768e10 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;
@@ -898,6 +901,9 @@ 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.
@@ -929,6 +935,19 @@ 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;
 };
 
 
@@ -1217,4 +1236,43 @@ extern const struct v4l2_subdev_ops v4l2_subdev_call_wrappers;
 void v4l2_subdev_notify_event(struct v4l2_subdev *sd,
 			      const struct v4l2_event *ev);
 
+/**
+ * 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 needed 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
-- 
2.25.1

[PATCH 3/6] 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 de160140d63b..779d7ae2262d 100644
--- a/drivers/media/v4l2-core/v4l2-subdev.c
+++ b/drivers/media/v4l2-core/v4l2-subdev.c
@@ -353,6 +353,44 @@ 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);
@@ -360,8 +398,11 @@ 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;
@@ -484,7 +525,7 @@ 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: {
@@ -495,7 +536,7 @@ 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: {
@@ -509,7 +550,7 @@ 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;
 
@@ -531,7 +572,7 @@ 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;
 
@@ -542,7 +583,7 @@ 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);
 	}
 
@@ -550,7 +591,7 @@ 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);
 	}
 
@@ -575,7 +616,7 @@ 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);
 	}
 
@@ -584,7 +625,7 @@ 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: {
@@ -595,7 +636,7 @@ 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: {
@@ -829,10 +870,13 @@ 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 4/6] 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.

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

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

diff --git a/drivers/media/platform/rcar-vin/rcar-v4l2.c b/drivers/media/platform/rcar-vin/rcar-v4l2.c
index 5aae01456c04..3759f4619a77 100644
--- a/drivers/media/platform/rcar-vin/rcar-v4l2.c
+++ b/drivers/media/platform/rcar-vin/rcar-v4l2.c
@@ -255,6 +255,7 @@ static int rvin_try_format(struct rvin_dev *vin, u32 which,
 {
 	struct v4l2_subdev *sd = vin_to_source(vin);
 	struct v4l2_subdev_state *sd_state;
+	static struct lock_class_key key;
 	struct v4l2_subdev_format format = {
 		.which = which,
 		.pad = vin->parallel.source_pad,
@@ -263,7 +264,11 @@ static int rvin_try_format(struct rvin_dev *vin, u32 which,
 	u32 width, height;
 	int ret;
 
-	sd_state = __v4l2_subdev_state_alloc(sd);
+	/*
+	 * FIXME: Drop this call, drivers are not supposed to use
+	 * __v4l2_subdev_state_alloc().
+	 */
+	sd_state = __v4l2_subdev_state_alloc(sd, "rvin:state->lock", &key);
 	if (IS_ERR(sd_state))
 		return PTR_ERR(sd_state);
 
diff --git a/drivers/media/platform/vsp1/vsp1_entity.c b/drivers/media/platform/vsp1/vsp1_entity.c
index 869cadc1468d..a116a3362f9e 100644
--- a/drivers/media/platform/vsp1/vsp1_entity.c
+++ b/drivers/media/platform/vsp1/vsp1_entity.c
@@ -613,6 +613,7 @@ int vsp1_entity_init(struct vsp1_device *vsp1, struct vsp1_entity *entity,
 		     const char *name, unsigned int num_pads,
 		     const struct v4l2_subdev_ops *ops, u32 function)
 {
+	static struct lock_class_key key;
 	struct v4l2_subdev *subdev;
 	unsigned int i;
 	int ret;
@@ -675,7 +676,12 @@ int vsp1_entity_init(struct vsp1_device *vsp1, struct vsp1_entity *entity,
 	 * Allocate the pad configuration to store formats and selection
 	 * rectangles.
 	 */
-	entity->config = __v4l2_subdev_state_alloc(&entity->subdev);
+	/*
+	 * FIXME: Drop this call, drivers are not supposed to use
+	 * __v4l2_subdev_state_alloc().
+	 */
+	entity->config = __v4l2_subdev_state_alloc(&entity->subdev,
+						   "vsp1:config->lock", &key);
 	if (IS_ERR(entity->config)) {
 		media_entity_cleanup(&entity->subdev.entity);
 		return PTR_ERR(entity->config);
diff --git a/drivers/media/v4l2-core/v4l2-subdev.c b/drivers/media/v4l2-core/v4l2-subdev.c
index 779d7ae2262d..5322329d396f 100644
--- a/drivers/media/v4l2-core/v4l2-subdev.c
+++ b/drivers/media/v4l2-core/v4l2-subdev.c
@@ -27,8 +27,9 @@
 static int subdev_fh_init(struct v4l2_subdev_fh *fh, struct v4l2_subdev *sd)
 {
 	struct v4l2_subdev_state *state;
+	static struct lock_class_key key;
 
-	state = __v4l2_subdev_state_alloc(sd);
+	state = __v4l2_subdev_state_alloc(sd, "fh->state->lock", &key);
 	if (IS_ERR(state))
 		return PTR_ERR(state);
 
@@ -914,7 +915,9 @@ int v4l2_subdev_link_validate(struct media_link *link)
 }
 EXPORT_SYMBOL_GPL(v4l2_subdev_link_validate);
 
-struct v4l2_subdev_state *__v4l2_subdev_state_alloc(struct v4l2_subdev *sd)
+struct v4l2_subdev_state *
+__v4l2_subdev_state_alloc(struct v4l2_subdev *sd, const char *lock_name,
+			  struct lock_class_key *lock_key)
 {
 	struct v4l2_subdev_state *state;
 	int ret;
@@ -923,6 +926,8 @@ struct v4l2_subdev_state *__v4l2_subdev_state_alloc(struct v4l2_subdev *sd)
 	if (!state)
 		return ERR_PTR(-ENOMEM);
 
+	__mutex_init(&state->lock, lock_name, lock_key);
+
 	if (sd->entity.num_pads) {
 		state->pads = kvmalloc_array(sd->entity.num_pads,
 					     sizeof(*state->pads),
@@ -954,6 +959,8 @@ void __v4l2_subdev_state_free(struct v4l2_subdev_state *state)
 	if (!state)
 		return;
 
+	mutex_destroy(&state->lock);
+
 	kvfree(state->pads);
 	kfree(state);
 }
@@ -988,11 +995,12 @@ void v4l2_subdev_notify_event(struct v4l2_subdev *sd,
 }
 EXPORT_SYMBOL_GPL(v4l2_subdev_notify_event);
 
-int v4l2_subdev_init_finalize(struct v4l2_subdev *sd)
+int __v4l2_subdev_init_finalize(struct v4l2_subdev *sd, const char *name,
+				struct lock_class_key *key)
 {
 	struct v4l2_subdev_state *state;
 
-	state = __v4l2_subdev_state_alloc(sd);
+	state = __v4l2_subdev_state_alloc(sd, name, key);
 	if (IS_ERR(state))
 		return PTR_ERR(state);
 
@@ -1000,7 +1008,7 @@ int v4l2_subdev_init_finalize(struct v4l2_subdev *sd)
 
 	return 0;
 }
-EXPORT_SYMBOL_GPL(v4l2_subdev_init_finalize);
+EXPORT_SYMBOL_GPL(__v4l2_subdev_init_finalize);
 
 void v4l2_subdev_cleanup(struct v4l2_subdev *sd)
 {
@@ -1008,3 +1016,23 @@ void v4l2_subdev_cleanup(struct v4l2_subdev *sd)
 	sd->active_state = NULL;
 }
 EXPORT_SYMBOL_GPL(v4l2_subdev_cleanup);
+
+struct v4l2_subdev_state *v4l2_subdev_lock_active_state(struct v4l2_subdev *sd)
+{
+	mutex_lock(&sd->active_state->lock);
+
+	return sd->active_state;
+}
+EXPORT_SYMBOL_GPL(v4l2_subdev_lock_active_state);
+
+void v4l2_subdev_lock_state(struct v4l2_subdev_state *state)
+{
+	mutex_lock(&state->lock);
+}
+EXPORT_SYMBOL_GPL(v4l2_subdev_lock_state);
+
+void v4l2_subdev_unlock_state(struct v4l2_subdev_state *state)
+{
+	mutex_unlock(&state->lock);
+}
+EXPORT_SYMBOL_GPL(v4l2_subdev_unlock_state);
diff --git a/drivers/staging/media/tegra-video/vi.c b/drivers/staging/media/tegra-video/vi.c
index b01f19e0f332..b366b56df15c 100644
--- a/drivers/staging/media/tegra-video/vi.c
+++ b/drivers/staging/media/tegra-video/vi.c
@@ -491,6 +491,7 @@ static int __tegra_channel_try_format(struct tegra_vi_channel *chan,
 				      struct v4l2_pix_format *pix)
 {
 	const struct tegra_video_format *fmtinfo;
+	static struct lock_class_key key;
 	struct v4l2_subdev *subdev;
 	struct v4l2_subdev_format fmt;
 	struct v4l2_subdev_state *sd_state;
@@ -507,7 +508,12 @@ static int __tegra_channel_try_format(struct tegra_vi_channel *chan,
 	if (!subdev)
 		return -ENODEV;
 
-	sd_state = __v4l2_subdev_state_alloc(subdev);
+	/*
+	 * FIXME: Drop this call, drivers are not supposed to use
+	 * __v4l2_subdev_state_alloc().
+	 */
+	sd_state = __v4l2_subdev_state_alloc(subdev, "tegra:state->lock",
+					     &key);
 	if (IS_ERR(sd_state))
 		return PTR_ERR(sd_state);
 	/*
diff --git a/include/media/v4l2-subdev.h b/include/media/v4l2-subdev.h
index eddf72768e10..80cd0ffb60d1 100644
--- a/include/media/v4l2-subdev.h
+++ b/include/media/v4l2-subdev.h
@@ -658,6 +658,7 @@ struct v4l2_subdev_pad_config {
 /**
  * struct v4l2_subdev_state - Used for storing subdev state information.
  *
+ * @lock: mutex for the state
  * @pads: &struct v4l2_subdev_pad_config array
  *
  * This structure only needs to be passed to the pad op if the 'which' field
@@ -665,6 +666,8 @@ struct v4l2_subdev_pad_config {
  * %V4L2_SUBDEV_FORMAT_ACTIVE it is safe to pass %NULL.
  */
 struct v4l2_subdev_state {
+	/* lock for the struct v4l2_subdev_state fields */
+	struct mutex lock;
 	struct v4l2_subdev_pad_config *pads;
 };
 
@@ -1157,10 +1160,14 @@ int v4l2_subdev_link_validate(struct media_link *link);
  * __v4l2_subdev_state_alloc - allocate v4l2_subdev_state
  *
  * @sd: pointer to &struct v4l2_subdev for which the state is being allocated.
+ * @lock_name: name of the state lock
+ * @key: lock_class_key for the lock
  *
  * Must call __v4l2_subdev_state_free() when state is no longer needed.
  */
-struct v4l2_subdev_state *__v4l2_subdev_state_alloc(struct v4l2_subdev *sd);
+struct v4l2_subdev_state *__v4l2_subdev_state_alloc(struct v4l2_subdev *sd,
+						    const char *lock_name,
+						    struct lock_class_key *key);
 
 /**
  * __v4l2_subdev_state_free - free a v4l2_subdev_state
@@ -1250,7 +1257,16 @@ void v4l2_subdev_notify_event(struct v4l2_subdev *sd,
  *
  * The user must call v4l2_subdev_cleanup() when the subdev is being removed.
  */
-int v4l2_subdev_init_finalize(struct v4l2_subdev *sd);
+#define v4l2_subdev_init_finalize(sd)                                          \
+	({                                                                     \
+		static struct lock_class_key __key;                            \
+		const char *name = KBUILD_BASENAME                             \
+			":" __stringify(__LINE__) ":subdev->state->lock";      \
+		__v4l2_subdev_init_finalize(sd, name, &__key);                 \
+	})
+
+int __v4l2_subdev_init_finalize(struct v4l2_subdev *sd, const char *name,
+				struct lock_class_key *key);
 
 /**
  * v4l2_subdev_cleanup() - Releases the resources needed by the subdevice
@@ -1275,4 +1291,34 @@ v4l2_subdev_get_active_state(struct v4l2_subdev *sd)
 	return sd->active_state;
 }
 
+/**
+ * v4l2_subdev_lock_active_state() - Locks and returns the active subdev state
+ *				     for the subdevice
+ * @sd: The subdevice
+ *
+ * Returns the locked active state for the subdevice, or NULL if the subdev
+ * does not support active state.
+ *
+ * The state must be unlocked with v4l2_subdev_unlock_state() after use.
+ */
+struct v4l2_subdev_state *v4l2_subdev_lock_active_state(struct v4l2_subdev *sd);
+
+/**
+ * v4l2_subdev_lock_state() - Locks the subdev state
+ * @state: The subdevice state
+ *
+ * Locks the given subdev state.
+ *
+ * The state must be unlocked with v4l2_subdev_unlock_state() after use.
+ */
+void v4l2_subdev_lock_state(struct v4l2_subdev_state *state);
+
+/**
+ * v4l2_subdev_unlock_state() - Unlocks the subdev state
+ * @state: The subdevice state
+ *
+ * Unlocks the given subdev state.
+ */
+void v4l2_subdev_unlock_state(struct v4l2_subdev_state *state);
+
 #endif
-- 
2.25.1

[PATCH 5/6] media: subdev: Add v4l2_subdev_lock_and_return_state()

[Tomi Valkeinen]

All suitable subdev ops are now passed either the TRY or the ACTIVE
state by the v4l2 core. However, other subdev drivers can still call the
ops passing NULL as the state, implying the active case.

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 here.

Signed-off-by: Tomi Valkeinen <tomi.valkeinen@ideasonboard.com>
Reviewed-by: Laurent Pinchart <laurent.pinchart@ideasonboard.com>
---
 include/media/v4l2-subdev.h | 35 +++++++++++++++++++++++++++++++++++
 1 file changed, 35 insertions(+)

diff --git a/include/media/v4l2-subdev.h b/include/media/v4l2-subdev.h
index 80cd0ffb60d1..4bc3cc04cc6e 100644
--- a/include/media/v4l2-subdev.h
+++ b/include/media/v4l2-subdev.h
@@ -8,6 +8,7 @@
 #ifndef _V4L2_SUBDEV_H
 #define _V4L2_SUBDEV_H
 
+#include "linux/dev_printk.h"
 #include <linux/types.h>
 #include <linux/v4l2-subdev.h>
 #include <media/media-entity.h>
@@ -1321,4 +1322,38 @@ void v4l2_subdev_lock_state(struct v4l2_subdev_state *state);
  */
 void v4l2_subdev_unlock_state(struct v4l2_subdev_state *state);
 
+/**
+ * v4l2_subdev_lock_and_return_state() - Gets locked try or active subdev state
+ * @sd: subdevice
+ * @state: subdevice state as passed to the subdev op
+ *
+ * Due to legacy reasons, when subdev drivers call ops in other subdevs they use
+ * NULL as the state parameter, as subdevs always used to have their active
+ * state stored privately.
+ *
+ * However, newer state-aware subdev drivers, which store their active state in
+ * a common place, subdev->active_state, expect to always get a proper state as
+ * a parameter.
+ *
+ * These state-aware drivers can use v4l2_subdev_lock_and_return_state() instead
+ * of v4l2_subdev_lock_state(). v4l2_subdev_lock_and_return_state() solves the
+ * issue by using subdev->state in case the passed state is NULL.
+ *
+ * This is a temporary helper function, and should be removed when we can ensure
+ * that all drivers pass proper state when calling other subdevs.
+ */
+static inline struct v4l2_subdev_state *
+v4l2_subdev_lock_and_return_state(struct v4l2_subdev *sd,
+				  struct v4l2_subdev_state *state)
+{
+	if (!state)
+		dev_notice_once(sd->dev, "source subdev should be ported to new state management\n");
+
+	state = state ? state : sd->active_state;
+
+	v4l2_subdev_lock_state(state);
+
+	return state;
+}
+
 #endif
-- 
2.25.1

[PATCH 6/6] 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>
---
 .../driver-api/media/v4l2-subdev.rst          | 58 +++++++++++++++++++
 1 file changed, 58 insertions(+)

diff --git a/Documentation/driver-api/media/v4l2-subdev.rst b/Documentation/driver-api/media/v4l2-subdev.rst
index 08ea2673b19e..f0ba04c80563 100644
--- a/Documentation/driver-api/media/v4l2-subdev.rst
+++ b/Documentation/driver-api/media/v4l2-subdev.rst
@@ -518,6 +518,64 @@ 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
+configuration for the subdev. This is often implemented e.g. as an array of
+struct v4l2_mbus_framefmt, one entry for each pad, and similarly for cropping
+and composition using struct v4l2_rect.
+
+In addition to the active configuration, each subdev filehandle has an array of
+struct v4l2_subdev_pad_config, managed by 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 associated with the sub-device itself as part of
+the :c:type:`v4l2_subdev` structure, while the core associates to each open
+file handle a try state, which contains the configuration valid in the
+file-handle context only.
+
+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 acquired resources before unregistering the sub-device.
+The core automatically initializes a state for each open file handle where to
+store the try configurations and releases them at file handle closing time.
+
+V4L2 sub-device operations that operate on both the :ref:`ACTIVE and TRY formats
+<v4l2-subdev-format-whence>` receive the correct state to operate on an
+operation parameter. The sub-device driver can access and modify the
+configuration stored in the provided state after having locked it by calling
+:c:func:`v4l2_subdev_lock_state()`. The driver must then call
+:c:func:`v4l2_subdev_unlock_state()` to unlock the state when done.
+
+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_active_state()`. The sub-device active state
+should equally be released by calling
+:c:func:`v4l2_subdev_unlock_state()`.
+
+In no occasions driver should try to manually access the state stored
+in the :c:type:`v4l2_subdev` or in the file handle without going
+through the designated helpers.
+
+The V4L2 core will pass either the try- or active-state to various subdev ops.
+Unfortunately not all the callers comply with this yet, and may pass NULL as
+the active-state. This is only a problem for subdev drivers which use the
+centrally managed active-state and are used in media pipelines with older
+subdev drivers. In these cases the called subdev ops must also handle the NULL
+case. This can be easily managed by the use of
+v4l2_subdev_validate_and_lock_state() helper.
+
+v4l2_subdev_validate_and_lock_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.
+
 V4L2 sub-device functions and data structures
 ---------------------------------------------
 
-- 
2.25.1

Re: [PATCH 5/6] media: subdev: Add v4l2_subdev_lock_and_return_state()

[Jacopo Mondi]

Hi Tomi,

On Fri, Dec 17, 2021 at 01:18:35PM +0200, Tomi Valkeinen wrote:
> All suitable subdev ops are now passed either the TRY or the ACTIVE
> state by the v4l2 core. However, other subdev drivers can still call the
> ops passing NULL as the state, implying the active case.
>
> 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 here.
>
> Signed-off-by: Tomi Valkeinen <tomi.valkeinen@ideasonboard.com>
> Reviewed-by: Laurent Pinchart <laurent.pinchart@ideasonboard.com>
> ---
>  include/media/v4l2-subdev.h | 35 +++++++++++++++++++++++++++++++++++
>  1 file changed, 35 insertions(+)
>
> diff --git a/include/media/v4l2-subdev.h b/include/media/v4l2-subdev.h
> index 80cd0ffb60d1..4bc3cc04cc6e 100644
> --- a/include/media/v4l2-subdev.h
> +++ b/include/media/v4l2-subdev.h
> @@ -8,6 +8,7 @@
>  #ifndef _V4L2_SUBDEV_H
>  #define _V4L2_SUBDEV_H
>
> +#include "linux/dev_printk.h"
>  #include <linux/types.h>
>  #include <linux/v4l2-subdev.h>
>  #include <media/media-entity.h>
> @@ -1321,4 +1322,38 @@ void v4l2_subdev_lock_state(struct v4l2_subdev_state *state);
>   */
>  void v4l2_subdev_unlock_state(struct v4l2_subdev_state *state);
>
> +/**
> + * v4l2_subdev_lock_and_return_state() - Gets locked try or active subdev state
> + * @sd: subdevice
> + * @state: subdevice state as passed to the subdev op
> + *
> + * Due to legacy reasons, when subdev drivers call ops in other subdevs they use
> + * NULL as the state parameter, as subdevs always used to have their active
> + * state stored privately.
> + *
> + * However, newer state-aware subdev drivers, which store their active state in
> + * a common place, subdev->active_state, expect to always get a proper state as
> + * a parameter.
> + *
> + * These state-aware drivers can use v4l2_subdev_lock_and_return_state() instead
> + * of v4l2_subdev_lock_state(). v4l2_subdev_lock_and_return_state() solves the
> + * issue by using subdev->state in case the passed state is NULL.
> + *
> + * This is a temporary helper function, and should be removed when we can ensure
> + * that all drivers pass proper state when calling other subdevs.
> + */
> +static inline struct v4l2_subdev_state *
> +v4l2_subdev_lock_and_return_state(struct v4l2_subdev *sd,
> +				  struct v4l2_subdev_state *state)
> +{
> +	if (!state)
> +		dev_notice_once(sd->dev, "source subdev should be ported to new state management\n");

I agree the message is improvable.
Maybe

		dev_notice_once(sd->dev, "The provided state is NULL. Adjusting to the subdev active state.\n");
		dev_notice_once(sd->dev, "Please consid er porting your driver to the new state management API.\n);

I don't mind multiple messages, other might.

Anyway, as long as we warn, I'm fine with this helper!

Reviewed-by: Jacopo Mondi <jacopo+renesas@jmondi.org>

Thanks
  j

> +
> +	state = state ? state : sd->active_state;
> +
> +	v4l2_subdev_lock_state(state);
> +
> +	return state;
> +}
> +
>  #endif
> --
> 2.25.1
>

Re: [PATCH 6/6] media: Documentation: add documentation about subdev state

[Hans Verkuil]

On 17/12/2021 12:18, Tomi Valkeinen wrote:
> Add documentation about centrally managed subdev state.
> 
> Signed-off-by: Tomi Valkeinen <tomi.valkeinen@ideasonboard.com>
> ---
>  .../driver-api/media/v4l2-subdev.rst          | 58 +++++++++++++++++++
>  1 file changed, 58 insertions(+)
> 
> diff --git a/Documentation/driver-api/media/v4l2-subdev.rst b/Documentation/driver-api/media/v4l2-subdev.rst
> index 08ea2673b19e..f0ba04c80563 100644
> --- a/Documentation/driver-api/media/v4l2-subdev.rst
> +++ b/Documentation/driver-api/media/v4l2-subdev.rst
> @@ -518,6 +518,64 @@ 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
> +configuration for the subdev. This is often implemented e.g. as an array of
> +struct v4l2_mbus_framefmt, one entry for each pad, and similarly for cropping
> +and composition using struct v4l2_rect.
> +
> +In addition to the active configuration, each subdev filehandle has an array of
> +struct v4l2_subdev_pad_config, managed by 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 associated with the sub-device itself as part of
> +the :c:type:`v4l2_subdev` structure, while the core associates to each open
> +file handle a try state, which contains the configuration valid in the
> +file-handle context only.
> +
> +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 acquired resources before unregistering the sub-device.
> +The core automatically initializes a state for each open file handle where to
> +store the try configurations and releases them at file handle closing time.
> +
> +V4L2 sub-device operations that operate on both the :ref:`ACTIVE and TRY formats

"operations that operate on": yuck.

How about: "operations that use"

> +<v4l2-subdev-format-whence>` receive the correct state to operate on an
> +operation parameter. The sub-device driver can access and modify the

"operate on an operation parameter"?

I think you mean: "operate on as a 'state' parameter"

> +configuration stored in the provided state after having locked it by calling
> +:c:func:`v4l2_subdev_lock_state()`. The driver must then call
> +:c:func:`v4l2_subdev_unlock_state()` to unlock the state when done.
> +
> +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_active_state()`. The sub-device active state
> +should equally be released by calling

should -> must

> +:c:func:`v4l2_subdev_unlock_state()`.
> +
> +In no occasions driver should try to manually access the state stored

In no occasions driver should try" -> "Drivers must never try"

> +in the :c:type:`v4l2_subdev` or in the file handle without going
> +through the designated helpers.
> +
> +The V4L2 core will pass either the try- or active-state to various subdev ops.
> +Unfortunately not all the callers comply with this yet, and may pass NULL as
> +the active-state. This is only a problem for subdev drivers which use the
> +centrally managed active-state and are used in media pipelines with older
> +subdev drivers. In these cases the called subdev ops must also handle the NULL
> +case. This can be easily managed by the use of
> +v4l2_subdev_validate_and_lock_state() helper.
> +
> +v4l2_subdev_validate_and_lock_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.
> +
>  V4L2 sub-device functions and data structures
>  ---------------------------------------------
>  
> 

Regards,

	Hans

Re: [PATCH 6/6] media: Documentation: add documentation about subdev state

[Jacopo Mondi]

Hi Tomi,

On Fri, Dec 17, 2021 at 01:18:36PM +0200, Tomi Valkeinen wrote:
> Add documentation about centrally managed subdev state.
>
> Signed-off-by: Tomi Valkeinen <tomi.valkeinen@ideasonboard.com>
> ---
>  .../driver-api/media/v4l2-subdev.rst          | 58 +++++++++++++++++++
>  1 file changed, 58 insertions(+)
>
> diff --git a/Documentation/driver-api/media/v4l2-subdev.rst b/Documentation/driver-api/media/v4l2-subdev.rst
> index 08ea2673b19e..f0ba04c80563 100644
> --- a/Documentation/driver-api/media/v4l2-subdev.rst
> +++ b/Documentation/driver-api/media/v4l2-subdev.rst
> @@ -518,6 +518,64 @@ 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
> +configuration for the subdev. This is often implemented e.g. as an array of

s/configuration for the subdev/device configuration/

to avoid repeating subdev

> +struct v4l2_mbus_framefmt, one entry for each pad, and similarly for cropping
> +and composition using struct v4l2_rect.

cropping and composition rectangles

> +
> +In addition to the active configuration, each subdev filehandle has an array of
> +struct v4l2_subdev_pad_config, managed by 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 associated with the sub-device itself as part of
> +the :c:type:`v4l2_subdev` structure, while the core associates to each open
> +file handle a try state, which contains the configuration valid in the
> +file-handle context only.

Three different spelling of file\.*handle :)

You're rightfully confused :)

~/project/linux$ git grep "file handle" Documentation/ | wc -l
92
~/project/linux$ git grep "filehandle" Documentation/ | wc -l
61
~/project/linux$ git grep "file-handle" Documentation/ | wc -l
1

> +
> +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 acquired resources before unregistering the sub-device.
> +The core automatically initializes a state for each open file handle where to
> +store the try configurations and releases them at file handle closing time.
> +
> +V4L2 sub-device operations that operate on both the :ref:`ACTIVE and TRY formats
> +<v4l2-subdev-format-whence>` receive the correct state to operate on an

s/an/as an/

> +operation parameter. The sub-device driver can access and modify the
> +configuration stored in the provided state after having locked it by calling
> +:c:func:`v4l2_subdev_lock_state()`. The driver must then call
> +:c:func:`v4l2_subdev_unlock_state()` to unlock the state when done.
> +
> +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_active_state()`. The sub-device active state
> +should equally be released by calling
> +:c:func:`v4l2_subdev_unlock_state()`.
> +
> +In no occasions driver should try to manually access the state stored
> +in the :c:type:`v4l2_subdev` or in the file handle without going
> +through the designated helpers.
> +
> +The V4L2 core will pass either the try- or active-state to various subdev ops.

What about making clear the issue is about callers of the kAPI ?

While the V4L2 core will pass the correct try- or active-state to the
subdevice operations, device drivers might call operations on other
subdevices by using :c:func:`v4l2_subdev_call()` kAPI.

> +Unfortunately not all the callers comply with this yet, and may pass NULL as

Unfortunately not all callers properly support subdevice state
handling yet, and may pass NULL as the state parameter.

> +the active-state. This is only a problem for subdev drivers which use the
> +centrally managed active-state and are used in media pipelines with older
> +subdev drivers. In these cases the called subdev ops must also handle the NULL
> +case. This can be easily managed by the use of
> +v4l2_subdev_validate_and_lock_state() helper.

Do you get the right linking without using :c:func:`..` ?

> +
> +v4l2_subdev_validate_and_lock_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.

Awesome!

Thanks for having brought this up to v11!
Reviewed-by: Jacopo Mondi <jacopo+renesas@jmondi.org>

Thanks
   j

> +
>  V4L2 sub-device functions and data structures
>  ---------------------------------------------
>
> --
> 2.25.1
>

Re: [PATCH 2/6] media: subdev: add active state to struct v4l2_subdev

[Jacopo Mondi]

Hi Tomi,

On Fri, Dec 17, 2021 at 01:18:32PM +0200, Tomi Valkeinen wrote:
> 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>
> ---
>  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 fe49c86a9b02..de160140d63b 100644
> --- a/drivers/media/v4l2-core/v4l2-subdev.c
> +++ b/drivers/media/v4l2-core/v4l2-subdev.c
> @@ -943,3 +943,24 @@ void v4l2_subdev_notify_event(struct v4l2_subdev *sd,
>  	v4l2_subdev_notify(sd, V4L2_DEVICE_NOTIFY_EVENT, (void *)ev);
>  }
>  EXPORT_SYMBOL_GPL(v4l2_subdev_notify_event);
> +
> +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);
> diff --git a/include/media/v4l2-subdev.h b/include/media/v4l2-subdev.h
> index e52bf508c75b..eddf72768e10 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;
> @@ -898,6 +901,9 @@ 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().

Is alignement a little off or is it my mail client ?
Nit apart:
Reviewed-by: Jacopo Mondi <jacopo+renesas@jmondi.org>

Thanks
   j

>   *
>   * Each instance of a subdev driver should create this struct, either
>   * stand-alone or embedded in a larger struct.
> @@ -929,6 +935,19 @@ 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;
>  };
>
>
> @@ -1217,4 +1236,43 @@ extern const struct v4l2_subdev_ops v4l2_subdev_call_wrappers;
>  void v4l2_subdev_notify_event(struct v4l2_subdev *sd,
>  			      const struct v4l2_event *ev);
>
> +/**
> + * 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 needed 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
> --
> 2.25.1
>

Re: [PATCH 2/6] media: subdev: add active state to struct v4l2_subdev

[Tomi Valkeinen]

On 17/12/2021 14:07, Jacopo Mondi wrote:
> Hi Tomi,
> 
> On Fri, Dec 17, 2021 at 01:18:32PM +0200, Tomi Valkeinen wrote:
>> 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>
>> ---
>>   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 fe49c86a9b02..de160140d63b 100644
>> --- a/drivers/media/v4l2-core/v4l2-subdev.c
>> +++ b/drivers/media/v4l2-core/v4l2-subdev.c
>> @@ -943,3 +943,24 @@ void v4l2_subdev_notify_event(struct v4l2_subdev *sd,
>>   	v4l2_subdev_notify(sd, V4L2_DEVICE_NOTIFY_EVENT, (void *)ev);
>>   }
>>   EXPORT_SYMBOL_GPL(v4l2_subdev_notify_event);
>> +
>> +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);
>> diff --git a/include/media/v4l2-subdev.h b/include/media/v4l2-subdev.h
>> index e52bf508c75b..eddf72768e10 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;
>> @@ -898,6 +901,9 @@ 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().
> 
> Is alignement a little off or is it my mail client ?

Looks correct to me. It's using tabs there. I don't like, I think it 
should be spaces, but I followed the convention used elsewhere.

  Tomi