From 009905ec50433259c05f474251000b040098564e Mon Sep 17 00:00:00 2001 From: Laurent Pinchart Date: Mon, 18 Sep 2023 15:48:38 +0300 Subject: media: v4l2-subdev: Document and enforce .s_stream() requirements The subdev .s_stream() operation must not be called to start an already started subdev, or stop an already stopped one. This requirement has never been formally documented. Fix it, and catch possible offenders with a WARN_ON() in the call_s_stream() wrapper. Signed-off-by: Laurent Pinchart Signed-off-by: Sakari Ailus Signed-off-by: Hans Verkuil --- drivers/media/v4l2-core/v4l2-subdev.c | 17 ++++++++++++++++- 1 file changed, 16 insertions(+), 1 deletion(-) (limited to 'drivers/media/v4l2-core') diff --git a/drivers/media/v4l2-core/v4l2-subdev.c b/drivers/media/v4l2-core/v4l2-subdev.c index b92348ad61f6..32b7d9cd43e6 100644 --- a/drivers/media/v4l2-core/v4l2-subdev.c +++ b/drivers/media/v4l2-core/v4l2-subdev.c @@ -359,6 +359,18 @@ static int call_s_stream(struct v4l2_subdev *sd, int enable) { int ret; + /* + * 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)) + return 0; + #if IS_REACHABLE(CONFIG_LEDS_CLASS) if (!IS_ERR_OR_NULL(sd->privacy_led)) { if (enable) @@ -372,9 +384,12 @@ static int call_s_stream(struct v4l2_subdev *sd, int enable) if (!enable && ret < 0) { dev_warn(sd->dev, "disabling streaming failed (%d)\n", ret); - return 0; + ret = 0; } + if (!ret) + sd->enabled_streams = enable ? BIT(0) : 0; + return ret; } -- cgit v1.2.3