Re: [RFC PATCH 02/11] drm/fb-helper: Skip writeback connectors

[Brian Starkey]

On Tue, Oct 11, 2016 at 05:44:48PM +0200, Daniel Vetter wrote:
> On Tue, Oct 11, 2016 at 03:53:59PM +0100, Brian Starkey wrote:
> > Writeback connectors aren't much use to the fbdev helpers, as they won't
> > show anything to the user. Skip them when looking for candidate output
> > configurations.
> >
> > Signed-off-by: Brian Starkey <brian.starkey@xxxxxxx>
> > ---
> >  drivers/gpu/drm/drm_fb_helper.c |    4 ++++
> >  1 file changed, 4 insertions(+)
> >
> > diff --git a/drivers/gpu/drm/drm_fb_helper.c b/drivers/gpu/drm/drm_fb_helper.c
> > index 03414bd..dedf6e7 100644
> > --- a/drivers/gpu/drm/drm_fb_helper.c
> > +++ b/drivers/gpu/drm/drm_fb_helper.c
> > @@ -2016,6 +2016,10 @@ static int drm_pick_crtcs(struct drm_fb_helper *fb_helper,
> >  	if (modes[n] == NULL)
> >  		return best_score;
> >
> > +	/* Writeback connectors aren't much use for fbdev */
> > +	if (connector->connector_type == DRM_MODE_CONNECTOR_WRITEBACK)
> > +		return best_score;
>
> I think we could handle this by always marking writeback connectors as
> disconnected. Userspace and fbdev emulation should then avoid them,
> always.
> -Daniel

Good idea; I'll need to take a closer look at how it would interact
with the probe helper (connector->force etc).

Are you thinking instead-of or in-addition-to the client cap? I'd be
worried about apps doing strange things and trying to use even
disconnected connectors.

> > +
> >  	crtcs = kzalloc(fb_helper->connector_count *
> >  			sizeof(struct drm_fb_helper_crtc *), GFP_KERNEL);
> >  	if (!crtcs)
> > --
> > 1.7.9.5
>
> --
> Daniel Vetter
> Software Engineer, Intel Corporation
> http://blog.ffwll.ch