linux-kernel - [PATCH v4 04/10] media: subdev: Fix use of sd->enabled_streams in call_s

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Message-Id: <20240416-enable-streams-impro-v4-4-1d370c9c2b6d@ideasonboard.com>
Date: Tue, 16 Apr 2024 13:40:03 +0300
From: Tomi Valkeinen <tomi.valkeinen@...asonboard.com>
To: Mauro Carvalho Chehab <mchehab@...nel.org>, 
 Hans Verkuil <hverkuil@...all.nl>, 
 Laurent Pinchart <laurent.pinchart@...asonboard.com>, 
 Sakari Ailus <sakari.ailus@...ux.intel.com>, 
 Umang Jain <umang.jain@...asonboard.com>
Cc: linux-media@...r.kernel.org, linux-kernel@...r.kernel.org, 
 Tomi Valkeinen <tomi.valkeinen@...asonboard.com>
Subject: [PATCH v4 04/10] media: subdev: Fix use of sd->enabled_streams in
 call_s_stream()

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, 's_stream_enabled', for
call_s_stream().

Reviewed-by: Umang Jain <umang.jain@...asonboard.com>
Reviewed-by: Laurent Pinchart <laurent.pinchart@...asonboard.com>
Signed-off-by: Tomi Valkeinen <tomi.valkeinen@...asonboard.com>
---
 drivers/media/v4l2-core/v4l2-subdev.c | 8 ++------
 include/media/v4l2-subdev.h           | 3 +++
 2 files changed, 5 insertions(+), 6 deletions(-)

diff --git a/drivers/media/v4l2-core/v4l2-subdev.c b/drivers/media/v4l2-core/v4l2-subdev.c
index 606a909cd778..941cf7be22c3 100644
--- a/drivers/media/v4l2-core/v4l2-subdev.c
+++ b/drivers/media/v4l2-core/v4l2-subdev.c
@@ -421,12 +421,8 @@ 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->s_stream_enabled == !!enable))
 		return 0;
 
 	ret = sd->ops->video->s_stream(sd, enable);
@@ -437,7 +433,7 @@ static int call_s_stream(struct v4l2_subdev *sd, int enable)
 	}
 
 	if (!ret) {
-		sd->enabled_streams = enable ? BIT(0) : 0;
+		sd->s_stream_enabled = enable;
 
 		if (enable)
 			v4l2_subdev_enable_privacy_led(sd);
diff --git a/include/media/v4l2-subdev.h b/include/media/v4l2-subdev.h
index a9e6b8146279..b3c3777db464 100644
--- a/include/media/v4l2-subdev.h
+++ b/include/media/v4l2-subdev.h
@@ -1043,6 +1043,8 @@ struct v4l2_subdev_platform_data {
  *		     v4l2_subdev_enable_streams() and
  *		     v4l2_subdev_disable_streams() helper functions for fallback
  *		     cases.
+ * @s_stream_enabled: Tracks whether streaming has been enabled with s_stream.
+ *                    This is only for call_s_stream() internal use.
  *
  * Each instance of a subdev driver should create this struct, either
  * stand-alone or embedded in a larger struct.
@@ -1091,6 +1093,7 @@ struct v4l2_subdev {
 	 */
 	struct v4l2_subdev_state *active_state;
 	u64 enabled_streams;
+	bool s_stream_enabled;
 };
 
 

-- 
2.34.1