Re: [01/30] drm: Introduce drm_bridge_init()

[Daniel Vetter <daniel@ffwll.ch>]

On Mon, Dec 02, 2019 at 05:55:06AM +0000, james qian wang (Arm Technology China) wrote:
> On Tue, Nov 26, 2019 at 01:15:59PM +0000, Mihail Atanassov wrote:
> > A simple convenience function to initialize the struct drm_bridge.
> > 
> > Signed-off-by: Mihail Atanassov <mihail.atanassov@arm.com>
> > ---
> >  drivers/gpu/drm/drm_bridge.c | 29 +++++++++++++++++++++++++++++
> >  include/drm/drm_bridge.h     |  4 ++++
> >  2 files changed, 33 insertions(+)
> > 
> > diff --git a/drivers/gpu/drm/drm_bridge.c b/drivers/gpu/drm/drm_bridge.c
> > index cba537c99e43..cbe680aa6eac 100644
> > --- a/drivers/gpu/drm/drm_bridge.c
> > +++ b/drivers/gpu/drm/drm_bridge.c
> > @@ -89,6 +89,35 @@ void drm_bridge_remove(struct drm_bridge *bridge)
> >  }
> >  EXPORT_SYMBOL(drm_bridge_remove);
> >  
> > +/**
> > + * drm_bridge_init - initialise a drm_bridge structure
> > + *
> > + * @bridge: bridge control structure
> > + * @funcs: control functions
> > + * @dev: device
> > + * @timings: timing specification for the bridge; optional (may be NULL)
> > + * @driver_private: pointer to the bridge driver internal context (may be NULL)
> > + */
> > +void drm_bridge_init(struct drm_bridge *bridge, struct device *dev,
> > +		     const struct drm_bridge_funcs *funcs,
> > +		     const struct drm_bridge_timings *timings,
> > +		     void *driver_private)
> > +{
> > +	WARN_ON(!funcs);
> > +
> > +	bridge->dev = NULL;
> > +	bridge->encoder = NULL;
> > +	bridge->next = NULL;
> > +
> > +#ifdef CONFIG_OF
> > +	bridge->of_node = dev->of_node;
> > +#endif
> > +	bridge->timings = timings;
> > +	bridge->funcs = funcs;
> > +	bridge->driver_private = driver_private;
> 
> Can we directly put drm_bridge_add() here. then
> - User always need to call bridge_init and add together.
> - Consistent with others like drm_plane/crtc_init which directly has
>   drm_mode_object_add() in it.

Uh no, the trouble here is that drm_bridge_add should actually be called
_register, because it publishes the bridge to the world. I think we even
have a todo item to rename _add to _register ... Once that's done the
bridge can't be changed anymore, all init code must have completed. So
often you need a bit of code between _init() and _register().

drm_mode_object_add is different since for mode objects it doesn't publish
it to the world, that's done with drm_dev_register and
drm_connector_register. drm_mode_object_add just does a bit of internal
house keeping.
-Daniel

> 
> James.
> > +}
> > +EXPORT_SYMBOL(drm_bridge_init);
> > +
> >  /**
> >   * drm_bridge_attach - attach the bridge to an encoder's chain
> >   *
> > diff --git a/include/drm/drm_bridge.h b/include/drm/drm_bridge.h
> > index c0a2286a81e9..d6d9d5301551 100644
> > --- a/include/drm/drm_bridge.h
> > +++ b/include/drm/drm_bridge.h
> > @@ -402,6 +402,10 @@ struct drm_bridge {
> >  
> >  void drm_bridge_add(struct drm_bridge *bridge);
> >  void drm_bridge_remove(struct drm_bridge *bridge);
> > +void drm_bridge_init(struct drm_bridge *bridge, struct device *dev,
> > +		     const struct drm_bridge_funcs *funcs,
> > +		     const struct drm_bridge_timings *timings,
> > +		     void *driver_private);
> >  struct drm_bridge *of_drm_find_bridge(struct device_node *np);
> >  int drm_bridge_attach(struct drm_encoder *encoder, struct drm_bridge *bridge,
> >  		      struct drm_bridge *previous);
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-- 
Daniel Vetter
Software Engineer, Intel Corporation
http://blog.ffwll.ch