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|---|---|
| State | Superseded |
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| Series |
media: subdev: Improve stream enable/disable machinery
|
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Commit Message
Tomi Valkeinen
April 5, 2024, 9:14 a.m. UTC
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 | 3 +++
2 files changed, 5 insertions(+), 6 deletions(-)
Comments
Moi, On Fri, Apr 05, 2024 at 12:14:22PM +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 | 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 a15a41576918..94483b238f2a 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->streaming_enabled == !!enable)) A single ! is enough on both sides. > return 0; > > if (enable) > @@ -442,7 +438,7 @@ static int call_s_stream(struct v4l2_subdev *sd, int enable) > } > > if (!ret) > - sd->enabled_streams = enable ? BIT(0) : 0; > + sd->streaming_enabled = !!enable; No need for !! unless you think it needs to be very loud. Casting a non-boolean value to boolean results in true if it's non-zero. > > return ret; > } > diff --git a/include/media/v4l2-subdev.h b/include/media/v4l2-subdev.h > index a9e6b8146279..f55d03e0acc1 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. > + * @streaming_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 streaming_enabled; > }; > > >
On 10/04/2024 13:05, Sakari Ailus wrote: > Moi, > > On Fri, Apr 05, 2024 at 12:14:22PM +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 | 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 a15a41576918..94483b238f2a 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->streaming_enabled == !!enable)) > > A single ! is enough on both sides. Or perhaps (sd->streaming_enabled == !!enable). > >> return 0; >> >> if (enable) >> @@ -442,7 +438,7 @@ static int call_s_stream(struct v4l2_subdev *sd, int enable) >> } >> >> if (!ret) >> - sd->enabled_streams = enable ? BIT(0) : 0; >> + sd->streaming_enabled = !!enable; > > No need for !! unless you think it needs to be very loud. Casting a > non-boolean value to boolean results in true if it's non-zero. Indeed. My coding style for booleans seems to be from times long past. Tomi > >> >> return ret; >> } >> diff --git a/include/media/v4l2-subdev.h b/include/media/v4l2-subdev.h >> index a9e6b8146279..f55d03e0acc1 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. >> + * @streaming_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 streaming_enabled; >> }; >> >> >> >
diff --git a/drivers/media/v4l2-core/v4l2-subdev.c b/drivers/media/v4l2-core/v4l2-subdev.c index a15a41576918..94483b238f2a 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->streaming_enabled == !!enable)) return 0; if (enable) @@ -442,7 +438,7 @@ 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..f55d03e0acc1 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. + * @streaming_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 streaming_enabled; };