Message-Id: <20231208-v4l2-state-mc-fix-v1-1-a0c8162557c6@ideasonboard.com>
Date:   Fri, 08 Dec 2023 18:15:15 +0200
From:   Tomi Valkeinen <tomi.valkeinen@...asonboard.com>
To:     Mauro Carvalho Chehab <mchehab@...nel.org>,
        Laurent Pinchart <laurent.pinchart@...asonboard.com>,
        Hans Verkuil <hverkuil-cisco@...all.nl>,
        Sakari Ailus <sakari.ailus@...ux.intel.com>
Cc:     linux-media@...r.kernel.org, linux-kernel@...r.kernel.org,
        Tomi Valkeinen <tomi.valkeinen@...asonboard.com>
Subject: [PATCH] media: v4l: subdev: Move out subdev state lock macros
 outside CONFIG_MEDIA_CONTROLLER

The subdev state locking macros and macros to get the active state are
currently behind CONFIG_MEDIA_CONTROLLER. This makes sense, as there can
be no subdev state without MC.

However, we have code paths common to MC and non-MC cases which call
subdev operations that have subdev state as a parameter. In the non-MC
case the state parameter would always be NULL.

Thus it makes sense to allow, e.g.:

v4l2_subdev_call_state_active(sd, pad, get_fmt, fmt)

which for non-MC case would call the subdev passing NULL as the state.

This currently fails:
https://lore.kernel.org/oe-kbuild-all/202312061101.PLrz5NnJ-lkp@intel.com/

Fix the issue by moving the related macros to be outside
CONFIG_MEDIA_CONTROLLER. The v4l2_subdev_lock_state() and
v4l2_subdev_unlock_state() macros will crash if given NULL as the state,
but the other macros behave correctly even when there's no active state,
and they will only call the lock/unlock macros if there is a state.

An alternative fix would be to make another version of
v4l2_subdev_call_state_try() with ifdefs, which would not use any state
macros and would always pass NULL as the state. But having two version
of a macro/function is always more confusing than having just one, so I
went this way.

So, this fixes the v4l2_subdev_call_state_active() macro. But we also
have v4l2_subdev_call_state_try(). It would be possible to fix that
macro by additionally creating "no-op" variants of the state alloc and
free functions. However, v4l2_subdev_call_state_try() is only used by a
single driver (stm32-dcmi), which selects MC, and the macro is supposed
to be removed as soon as the users have been converted away from the
macro. Thus I have not touched the state alloc/free functions, and I
think it makes sense to keep alloc/free functions available only if
there's actually something that can be allocated or freed.

Signed-off-by: Tomi Valkeinen <tomi.valkeinen@...asonboard.com>
---
 include/media/v4l2-subdev.h | 166 ++++++++++++++++++++++----------------------
 1 file changed, 83 insertions(+), 83 deletions(-)

diff --git a/include/media/v4l2-subdev.h b/include/media/v4l2-subdev.h
index 8b08f6640dee..61024a74ce38 100644
--- a/include/media/v4l2-subdev.h
+++ b/include/media/v4l2-subdev.h
@@ -1311,89 +1311,6 @@ int __v4l2_subdev_init_finalize(struct v4l2_subdev *sd, const char *name,
  */
 void v4l2_subdev_cleanup(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.
- */
-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. 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_lock_and_get_active_state(struct v4l2_subdev *sd)
-{
-	if (sd->active_state)
-		v4l2_subdev_lock_state(sd->active_state);
-	return sd->active_state;
-}
-
 /*
  * A macro to generate the macro or function name for sub-devices state access
  * wrapper macros below.
@@ -1738,6 +1655,89 @@ int v4l2_subdev_s_stream_helper(struct v4l2_subdev *sd, int enable);
 
 #endif /* CONFIG_MEDIA_CONTROLLER */
 
+/**
+ * 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. 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_lock_and_get_active_state(struct v4l2_subdev *sd)
+{
+	if (sd->active_state)
+		v4l2_subdev_lock_state(sd->active_state);
+	return sd->active_state;
+}
+
 /**
  * v4l2_subdev_init - initializes the sub-device struct
  *

---
base-commit: e55a9482888da73eeadde5f13ef8bafce68a38ed
change-id: 20231208-v4l2-state-mc-fix-b4f0ebfbb2bf

Best regards,
-- 
Tomi Valkeinen <tomi.valkeinen@...asonboard.com>

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