Re: [Intel-gfx] [PATCH 1/3] drm: Make sure at least one plane supports the fb format

From: Eric Anholt <eric@anholt.net>
To: "Ville Syrjälä" <ville.syrjala@linux.intel.com>
Cc: intel-gfx@lists.freedesktop.org, dri-devel@lists.freedesktop.org
Subject: Re: [Intel-gfx] [PATCH 1/3] drm: Make sure at least one plane supports the fb format
Date: Mon, 05 Mar 2018 14:56:59 -0800	[thread overview]
Message-ID: <87woyq6shw.fsf@anholt.net> (raw)
In-Reply-To: <20180305211500.GY5453@intel.com>

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Ville Syrjälä <ville.syrjala@linux.intel.com> writes:

> On Mon, Mar 05, 2018 at 12:59:00PM -0800, Eric Anholt wrote:
>> Ville Syrjala <ville.syrjala@linux.intel.com> writes:
>> 
>> > From: Ville Syrjälä <ville.syrjala@linux.intel.com>
>> >
>> > To make life easier for drivers, let's have the core check that the
>> > requested pixel format is supported by at least one plane when creating
>> > a new framebuffer.
>> >
>> > Signed-off-by: Ville Syrjälä <ville.syrjala@linux.intel.com>
>> > ---
>> >  drivers/gpu/drm/drm_framebuffer.c | 26 ++++++++++++++++++++++++++
>> >  1 file changed, 26 insertions(+)
>> >
>> > diff --git a/drivers/gpu/drm/drm_framebuffer.c b/drivers/gpu/drm/drm_framebuffer.c
>> > index c0530a1af5e3..155b21e579c4 100644
>> > --- a/drivers/gpu/drm/drm_framebuffer.c
>> > +++ b/drivers/gpu/drm/drm_framebuffer.c
>> > @@ -152,6 +152,23 @@ static int fb_plane_height(int height,
>> >  	return DIV_ROUND_UP(height, format->vsub);
>> >  }
>> >  
>> > +static bool planes_have_format(struct drm_device *dev, u32 format)
>> > +{
>> > +	struct drm_plane *plane;
>> > +
>> > +	/* TODO: maybe maintain a device level format list? */
>> > +	drm_for_each_plane(plane, dev) {
>> > +		int i;
>> > +
>> > +		for (i = 0; i < plane->format_count; i++) {
>> > +			if (plane->format_types[i] == format)
>> > +				return true;
>> > +		}
>> > +	}
>> > +
>> > +	return false;
>> > +}
>> > +
>> >  static int framebuffer_check(struct drm_device *dev,
>> >  			     const struct drm_mode_fb_cmd2 *r)
>> >  {
>> > @@ -168,6 +185,15 @@ static int framebuffer_check(struct drm_device *dev,
>> >  		return -EINVAL;
>> >  	}
>> >  
>> > +	if (!planes_have_format(dev, r->pixel_format)) {
>> > +		struct drm_format_name_buf format_name;
>> > +
>> > +		DRM_DEBUG_KMS("unsupported framebuffer format %s\n",
>> > +			      drm_get_format_name(r->pixel_format,
>> > +						  &format_name));
>> > +		return -EINVAL;
>> > +	}
>> > +
>> 
>> Won't this break KMS on things like the radeon driver, which doesn't do
>> planes?  Maybe check if any universal planes have been registered and
>> only do the check in that case?
>
> Hmm. I thought we add the implicit planes always. Apparently
> drm_crtc_init() adds a primary with X/ARGB8888, but no more. So
> this would break all other formats, which is probably a bit too
> aggressive.
>
> I guess I could just skip the check in case any plane has
> plane->format_default set. That should be indicating that the driver
> doesn't do planes fully. Oh, why exactly is amggpu setting that flag?
> Harry?
>
>> 
>> Also, "any_planes_have_format()" might be slightly more descriptive.
>
> Or any_plane_has_format()? Is that more englishy? :)

I like it.

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