linux-kernel - Re: [PATCH] drm: Auto-set allow_fb_modifiers when given modifiers at plane init

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Date:   Mon, 7 Jan 2019 11:49:16 +0100
From:   Daniel Vetter <daniel@...ll.ch>
To:     Paul Kocialkowski <paul.kocialkowski@...tlin.com>
Cc:     dri-devel@...ts.freedesktop.org, linux-kernel@...r.kernel.org,
        Maarten Lankhorst <maarten.lankhorst@...ux.intel.com>,
        Eric Anholt <eric@...olt.net>, Sean Paul <sean@...rly.run>,
        David Airlie <airlied@...ux.ie>,
        Thomas Petazzoni <thomas.petazzoni@...tlin.com>,
        Daniel Vetter <daniel@...ll.ch>
Subject: Re: [PATCH] drm: Auto-set allow_fb_modifiers when given modifiers at
 plane init

On Fri, Jan 04, 2019 at 09:56:10AM +0100, Paul Kocialkowski wrote:
> When drivers pass non-empty lists of modifiers for initializing their
> planes, we can infer that they allow framebuffer modifiers and set the
> driver's allow_fb_modifiers mode config element.
> 
> In case the allow_fb_modifiers element was not set (some drivers tend
> to set them after registering planes), the modifiers will still be
> registered but won't be available to userspace unless the flag is set
> later. However in that case, the IN_FORMATS blob won't be created.
> 
> In order to avoid this case and generally reduce the trouble associated
> with the flag, always set allow_fb_modifiers when a non-empty list of
> format modifiers is passed at plane init.
> 
> Signed-off-by: Paul Kocialkowski <paul.kocialkowski@...tlin.com>

The automatic primary plane drm_crtc_init() creates doesn't set this, so
looks correct in all cases.

Reviewed-by: Daniel Vetter <daniel.vetter@...ll.ch>

(boolin.com has a bunch of drm-misc committers, so I'll leave pushing to
them).
-Daniel

> ---
>  drivers/gpu/drm/drm_plane.c | 3 +++
>  1 file changed, 3 insertions(+)
> 
> diff --git a/drivers/gpu/drm/drm_plane.c b/drivers/gpu/drm/drm_plane.c
> index 5f650d8fc66b..4cfb56893b7f 100644
> --- a/drivers/gpu/drm/drm_plane.c
> +++ b/drivers/gpu/drm/drm_plane.c
> @@ -220,6 +220,9 @@ int drm_universal_plane_init(struct drm_device *dev, struct drm_plane *plane,
>  			format_modifier_count++;
>  	}
>  
> +	if (format_modifier_count)
> +		config->allow_fb_modifiers = true;
> +
>  	plane->modifier_count = format_modifier_count;
>  	plane->modifiers = kmalloc_array(format_modifier_count,
>  					 sizeof(format_modifiers[0]),
> -- 
> 2.20.1
> 

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