[PATCH] drm/probe-helper: Fix modes reporting for writeback connector

[Daniel Vetter]

On Thu, Jul 12, 2018 at 10:20:35AM +0100, Alexandru-Cosmin Gheorghe wrote:
> On Thu, Jul 12, 2018 at 10:55:47AM +0200, Daniel Vetter wrote:
> > On Thu, Jul 12, 2018 at 09:48:02AM +0100, Alexandru Gheorghe wrote:
> > > Writeback connector is reported as disconnected, currently this causes
> > > the setting of the edid property to null and then exit.
> > > In order to properly get the modes for writeback we need to add an
> > > exception when connector type is DRM_MODE_CONNECTOR_WRITEBACK.
> > > 
> > > Signed-off-by: Alexandru Gheorghe <alexandru-cosmin.gheorghe at arm.com>
> > 
> > Why do you even need a mode list for writeback?
> 
> It's used by userspace to know how big the writeback buffer could be.
> 
> > 
> > Also, if you're already faking a mode list for the writeback connector,
> > why can't you also fake it's connection status?
> > -Daniel
> 
> AFAIK Reporting it as disconnected was a way of making sure it will be
> ignored by userspace that's not aware of writeback connectorsa. Do you
> think it's superfluous with DRM_CLIENT_CAP_WRITEBACK_CONNECTORS ?

Yes, since we're filtering writeback connectors from userspace that can't
deal with them I think a cleaner solution would be to just mark them as
connected. Old userspace won't ever see them, new userspace should already
correctly ignore them.
-Daniel

> 
> > 
> > > ---
> > >  drivers/gpu/drm/drm_probe_helper.c | 3 ++-
> > >  1 file changed, 2 insertions(+), 1 deletion(-)
> > > 
> > > diff --git a/drivers/gpu/drm/drm_probe_helper.c b/drivers/gpu/drm/drm_probe_helper.c
> > > index 52774339..c7bdbe2 100644
> > > --- a/drivers/gpu/drm/drm_probe_helper.c
> > > +++ b/drivers/gpu/drm/drm_probe_helper.c
> > > @@ -472,7 +472,8 @@ int drm_helper_probe_single_connector_modes(struct drm_connector *connector,
> > >  
> > >  	dev->mode_config.poll_running = drm_kms_helper_poll;
> > >  
> > > -	if (connector->status == connector_status_disconnected) {
> > > +	if (connector->status == connector_status_disconnected &&
> > > +	    connector->connector_type != DRM_MODE_CONNECTOR_WRITEBACK) {
> > >  		DRM_DEBUG_KMS("[CONNECTOR:%d:%s] disconnected\n",
> > >  			connector->base.id, connector->name);
> > >  		drm_mode_connector_update_edid_property(connector, NULL);
> > > -- 
> > > 2.7.4
> > > 
> > > _______________________________________________
> > > dri-devel mailing list
> > > dri-devel at lists.freedesktop.org
> > > https://lists.freedesktop.org/mailman/listinfo/dri-devel
> > 
> > -- 
> > Daniel Vetter
> > Software Engineer, Intel Corporation
> > http://blog.ffwll.ch
> 
> -- 
> Cheers,
> Alex G

-- 
Daniel Vetter
Software Engineer, Intel Corporation
http://blog.ffwll.ch