On Thu, Jan 16, 2025 at 02:43:37AM +0200, Dmitry Baryshkov wrote:
> On Wed, Jan 15, 2025 at 10:05:30PM +0100, Maxime Ripard wrote:
> > The current bridge state is accessible from the drm_bridge structure,
> > but since it's fairly indirect it's not easy to figure out.
> >
> > Provide a helper to retrieve it.
> >
> > Signed-off-by: Maxime Ripard <mripard@xxxxxxxxxx>
> > ---
> > include/drm/drm_bridge.h | 17 +++++++++++++++++
> > 1 file changed, 17 insertions(+)
> >
> > diff --git a/include/drm/drm_bridge.h b/include/drm/drm_bridge.h
> > index 8e18130be8bb85fc2463917dde9bf1d281934184..95c5037a6335e4c1be511e6c31308202015c7754 100644
> > --- a/include/drm/drm_bridge.h
> > +++ b/include/drm/drm_bridge.h
> > @@ -955,10 +955,27 @@ static inline struct drm_bridge *of_drm_find_bridge(struct device_node *np)
> > {
> > return NULL;
> > }
> > #endif
> >
> > +/**
> > + * @drm_bridge_get_current_state() - Get the current bridge state
> > + * @bridge: bridge object
> > + *
> > + * RETURNS:
> > + *
> > + * The current bridge state, or NULL if there is none.
>
> Are there any kind of limitations on when and how this function can be
> used? I don't think we can be accessing the state randomly, as the
> framework can change it at some points. E.g. what if the driver uses
> this state from audio or cec callbacks, while the DRM framework performs
> atomic commit and changes / frees the state right concurrently?
Yeah you can only look at this when either holding the corresponding
modesetlock, or in atomic commit. But in the latter it's a much cleaner
design pattern to instead look up the state from the drm_atomic_state,
since that pointer is the magic thing which guarantees lifetim/ownership
for lockless access in atomic commit code.
-Sima
>
> > + */
> > +static inline struct drm_bridge_state *
> > +drm_bridge_get_current_state(struct drm_bridge *bridge)
> > +{
> > + if (!bridge)
> > + return NULL;
> > +
> > + return drm_priv_to_bridge_state(bridge->base.state);
> > +}
> > +
> > /**
> > * drm_bridge_get_next_bridge() - Get the next bridge in the chain
> > * @bridge: bridge object
> > *
> > * RETURNS:
> >
> > --
> > 2.47.1
> >
>
> --
> With best wishes
> Dmitry
--
Simona Vetter
Software Engineer, Intel Corporation
http://blog.ffwll.ch
