Re: [PATCH 06/13] drm: add atomic hook to read property plus helper

[Daniel Vetter <daniel@ffwll.ch>]

On Wed, Dec 17, 2014 at 09:15:12AM -0500, Rob Clark wrote:
> On Wed, Dec 17, 2014 at 9:06 AM, Daniel Vetter <daniel@ffwll.ch> wrote:
> > On Wed, Dec 17, 2014 at 03:02:41PM +0100, Daniel Vetter wrote:
> >> On Tue, Dec 16, 2014 at 06:05:34PM -0500, Rob Clark wrote:
> >> > Once a driver is using atomic helpers for modeset, the next step is to
> >> > switch over to atomic properties.  To do this, plug in the helper
> >> > function to your modeconfig funcs and be sure to implement the plane/
> >> > crtc/connector atomic_{get,set}_property vfuncs for any of your mode-
> >> > objects which have driver custom properties.
> >> >
> >> > Signed-off-by: Rob Clark <robdclark@gmail.com>
> >> > ---
> >> >  drivers/gpu/drm/drm_atomic_helper.c | 46 +++++++++++++++++++++++++++++++++++++
> >> >  drivers/gpu/drm/drm_crtc.c          |  9 ++++++++
> >> >  include/drm/drm_atomic_helper.h     |  2 ++
> >> >  include/drm/drm_crtc.h              |  3 +++
> >> >  4 files changed, 60 insertions(+)
> >> >
> >> > diff --git a/drivers/gpu/drm/drm_atomic_helper.c b/drivers/gpu/drm/drm_atomic_helper.c
> >> > index d42fdb1..1a1ab34 100644
> >> > --- a/drivers/gpu/drm/drm_atomic_helper.c
> >> > +++ b/drivers/gpu/drm/drm_atomic_helper.c
> >> > @@ -1703,6 +1703,52 @@ backoff:
> >> >  EXPORT_SYMBOL(drm_atomic_helper_connector_set_property);
> >> >
> >> >  /**
> >> > + * drm_atomic_helper_get_property - helper to read atomic property
> >> > + * @obj: drm mode object whose property to read
> >> > + * @property: the property to read
> >> > + * @val: the read value, returned by reference
> >> > + *
> >> > + * RETURNS:
> >> > + * Zero on success, error code on failure
> >> > + */
> >> > +int drm_atomic_helper_get_property(struct drm_mode_object *obj,
> >> > +           struct drm_property *property, uint64_t *val)
> >> > +{
> >> > +   struct drm_device *dev = property->dev;
> >> > +   int ret;
> >> > +
> >> > +   switch (obj->type) {
> >> > +   case DRM_MODE_OBJECT_CONNECTOR: {
> >> > +           struct drm_connector *connector = obj_to_connector(obj);
> >> > +           WARN_ON(!drm_modeset_is_locked(&dev->mode_config.connection_mutex));
> >> > +           ret = connector->funcs->atomic_get_property(connector,
> >> > +                           connector->state, property, val);
> >>
> >> Shouldn't we use the get helpers introduced in previous patches here? For
> >> legacy support we definitely want old core stuff like dpms to keep
> >> working. Of course that means all the new atomic properties won't get
> >> magically filtered out. But I think we need to hide them explicitly
> >> anyway, e.g. with a new DRM_MODE_PROP_ATOMIC and checking for that in
> >> legacy paths.
> >
> > Also I'm not sure if there's a benefit to make this a vfunc+helper instead
> > of just core code called unconditionally. Meaning I can't think of any
> > case where drivers want to overwrite this, ever. They can do all the fancy
> > they want for their private properties in the per-object hooks. And for
> > core/shared stuff we better not allow them to play with fire.
> >
> > Or do I miss an important case here?
> 
> drivers can have their own custom properties too :-)
> 
> umm, or are you talking about the vfunc in config->funcs?  (In which
> case, it was at least a convenient way to for core to know whether to
> take legacy path or atomic path)

Yeah I only meant the config->func hook. Is there no other way to handle
this in the core? It looks funny if we use a func pointer essentially as a
boolean and don't allow drivers to set anything else than the defaults.
Essentially makes the helpers mandatory. Maybe just have
bool config->use_atomic_properties instead?
-Daniel
-- 
Daniel Vetter
Software Engineer, Intel Corporation
+41 (0) 79 365 57 48 - http://blog.ffwll.ch
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