| Message ID | 20240404-enable-streams-impro-v1-2-1017a35bbe07@ideasonboard.com (mailing list archive) |
|---|---|
| State | New, archived |
| Headers | show |
| Series | media: subdev: Improve stream enable/disable machinery | expand |
Hi Tomi, Thank you for the patch. On Thu, Apr 04, 2024 at 01:50:01PM +0300, Tomi Valkeinen wrote: > 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. Could you extend this to indicate this field can't be used by anything else than call_s_stream() ? I'm also getting a bit concerned about having multiple fields with similar purposes. Another option would be to call the .s_stream() operation directly from the fallback handlers, instead of going through call_s_stream(). That may be considered as a bit of a hack though. > * > * 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; > }; > >
On 04/04/2024 16:00, Laurent Pinchart wrote: > Hi Tomi, > > Thank you for the patch. > > On Thu, Apr 04, 2024 at 01:50:01PM +0300, Tomi Valkeinen wrote: >> 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. > > Could you extend this to indicate this field can't be used by anything > else than call_s_stream() ? Yes, I'll add that. > I'm also getting a bit concerned about having multiple fields with > similar purposes. Another option would be to call the .s_stream() I agree, it's getting slightly complex. The reason is that we support many ways for the subdev to implement these things. > operation directly from the fallback handlers, instead of going through > call_s_stream(). That may be considered as a bit of a hack though. I thought about the same thing, but I felt it might just make things more complex. However, with my new unsent series, I add the privacy_led code also to the v4l2_subdev_enable_streams() function, so it's even more similar to the call_s_stream. Maybe I'll try it out and see how it looks like if I call the op directly. Tomi >> * >> * 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; >> }; >> >> >
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; };
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(-)