linux-kernel - Re: [PATCH] drm/vc4: Allow fb modifiers early enough to fill IN

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Message-ID: <20181228120848.GS9058@dvetter-linux.ger.corp.intel.com>
Date:   Fri, 28 Dec 2018 13:08:48 +0100
From:   Daniel Vetter <daniel@...ll.ch>
To:     Eric Anholt <eric@...olt.net>
Cc:     Paul Kocialkowski <paul.kocialkowski@...tlin.com>,
        dri-devel@...ts.freedesktop.org, linux-kernel@...r.kernel.org,
        David Airlie <airlied@...ux.ie>,
        Maxime Ripard <maxime.ripard@...tlin.com>,
        Thomas Petazzoni <thomas.petazzoni@...tlin.com>,
        Eben Upton <eben@...pberrypi.org>
Subject: Re: [PATCH] drm/vc4: Allow fb modifiers early enough to fill
 IN_FORMATS property

On Thu, Dec 27, 2018 at 03:36:20PM -0800, Eric Anholt wrote:
> Paul Kocialkowski <paul.kocialkowski@...tlin.com> writes:
> 
> > The KMS mode_config elements are currently configured in vc4_kms_load,
> > that is called after all components are binded (component_bind_all).
> > However, the CRTC component (for the Pixel Valve) needs to access the
> > allow_fb_modifiers element at bind time, when initializing its planes
> > through drm_universal_plane_init.
> >
> > This helpers checks allow_fb_modifiers to decide whether to fill the
> > IN_FORMATS property. Because allow_fb_modifiers is still set to false
> > at this point, the property is never filled and userspace cannot
> > retrieve the combination of supported formats and modifiers.
> >
> > Fix this by setting allow_fb_modifiers right after calling
> > drm_mode_config_init (which initializes the structure), before binding
> > the components of the driver.
> 
> This makes me wonder if the flag could be removed and replaced with "did
> non-NULL modifiers get supplied to plane init?"  I think I've tripped
> over this flag in other KMS hacking, too.

Sounds like a good idea to me. Just setting it in plane_init should work I
think ...
-Daniel
-- 
Daniel Vetter
Software Engineer, Intel Corporation
http://blog.ffwll.ch