[PATCH 2/4] media: subdev: Fix use of sd->enabled_streams in call_s_stream()

Tomi Valkeinen
2024-04-04T10:50:23Z

call_s_stream() uses sd->enabled_streams to track whether streaming has
already been enabled. However,
v4l2_subdev_enable/disable_streams_fallback(), which was the original
user of this field, already uses it, and
v4l2_subdev_enable/disable_streams_fallback() will call call_s_stream().

This leads to a conflict as both functions set the field. Afaics, both
functions set the field to the same value, so it won't cause a runtime
bug, but it's still wrong and if we, e.g., change how
v4l2_subdev_enable/disable_streams_fallback() operates we might easily
cause bugs.

Fix this by adding a new field, 'streaming_enabled', for
call_s_stream().

Signed-off-by: Tomi Valkeinen <tomi.valkeinen@ideasonboard.com>
---
drivers/media/v4l2-core/v4l2-subdev.c | 8 ++------
include/media/v4l2-subdev.h | 2 ++
2 files changed, 4 insertions(+), 6 deletions(-)

diff --git a/drivers/media/v4l2-core/v4l2-subdev.c b/drivers/media/v4l2-core/v4l2-subdev.c
index b90b5185e87f..3b3310bce5d4 100644
--- a/drivers/media/v4l2-core/v4l2-subdev.c
+++ b/drivers/media/v4l2-core/v4l2-subdev.c
@@ -404,12 +404,8 @@ static int call_s_stream(struct v4l2_subdev *sd, int enable)
* The .s_stream() operation must never be called to start or stop an
* already started or stopped subdev. Catch offenders but don't return
* an error yet to avoid regressions.
- *
- * As .s_stream() is mutually exclusive with the .enable_streams() and
- * .disable_streams() operation, we can use the enabled_streams field
- * to store the subdev streaming state.
*/
- if (WARN_ON(!!sd->enabled_streams == !!enable))
+ if (WARN_ON(!!sd->streaming_enabled == !!enable))
return 0;

#if IS_REACHABLE(CONFIG_LEDS_CLASS)
@@ -429,7 +425,7 @@ static int call_s_stream(struct v4l2_subdev *sd, int enable)
}

if (!ret)
- sd->enabled_streams = enable ? BIT(0) : 0;
+ sd->streaming_enabled = !!enable;

return ret;
}
diff --git a/include/media/v4l2-subdev.h b/include/media/v4l2-subdev.h
index a9e6b8146279..8bd1e3c96d2b 100644
--- a/include/media/v4l2-subdev.h
+++ b/include/media/v4l2-subdev.h
@@ -1043,6 +1043,7 @@ struct v4l2_subdev_platform_data {
* v4l2_subdev_enable_streams() and
* v4l2_subdev_disable_streams() helper functions for fallback
* cases.
+ * @streaming_enabled: Tracks whether streaming has been enabled with s_stream.
*
* Each instance of a subdev driver should create this struct, either
* stand-alone or embedded in a larger struct.
@@ -1091,6 +1092,7 @@ struct v4l2_subdev {
*/
struct v4l2_subdev_state *active_state;
u64 enabled_streams;
+ bool streaming_enabled;
};

--
2.34.1