linux-kernel - Re: [PATCH 3/3] drm: zynqmp: Add blend mode property to graphics plane

lists.openwall.net		lists / announce owl-users owl-dev john-users john-dev passwdqc-users yescrypt popa3d-users / oss-security kernel-hardening musl sabotage tlsify passwords / crypt-dev xvendor / Bugtraq Full-Disclosure linux-kernel linux-netdev linux-ext4 linux-hardening linux-cve-announce PHC
Open Source and information security mailing list archives

Hash Suite: Windows password security audit tool. GUI, reports in PDF.

[<prev] [next>] [<thread-prev] [thread-next>] [day] [month] [year] [list]

Message-ID: <b97065ce-2dc0-453b-ab8e-b2d134fc3467@linux.dev>
Date: Thu, 13 Nov 2025 18:07:07 -0500
From: Sean Anderson <sean.anderson@...ux.dev>
To: "Klymenko, Anatoliy" <Anatoliy.Klymenko@....com>,
 Laurent Pinchart <laurent.pinchart@...asonboard.com>,
 Tomi Valkeinen <tomi.valkeinen@...asonboard.com>,
 "dri-devel@...ts.freedesktop.org" <dri-devel@...ts.freedesktop.org>
Cc: "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
 Mike Looijmans <mike.looijmans@...ic.nl>, David Airlie <airlied@...il.com>,
 Thomas Zimmermann <tzimmermann@...e.de>,
 Maarten Lankhorst <maarten.lankhorst@...ux.intel.com>,
 Maxime Ripard <mripard@...nel.org>,
 "linux-arm-kernel@...ts.infradead.org"
 <linux-arm-kernel@...ts.infradead.org>, Simona Vetter <simona@...ll.ch>,
 "Simek, Michal" <michal.simek@....com>
Subject: Re: [PATCH 3/3] drm: zynqmp: Add blend mode property to graphics
 plane

On 11/13/25 18:03, Klymenko, Anatoliy wrote:
> [AMD Official Use Only - AMD Internal Distribution Only]
> 
> Hi Sean,
> 
> Thank you for the patch.
> 
>> -----Original Message-----
>> From: Sean Anderson <sean.anderson@...ux.dev>
>> Sent: Thursday, November 13, 2025 12:37 PM
>> To: Laurent Pinchart <laurent.pinchart@...asonboard.com>; Tomi Valkeinen
>> <tomi.valkeinen@...asonboard.com>; dri-devel@...ts.freedesktop.org
>> Cc: linux-kernel@...r.kernel.org; Mike Looijmans <mike.looijmans@...ic.nl>;
>> David Airlie <airlied@...il.com>; Thomas Zimmermann
>> <tzimmermann@...e.de>; Maarten Lankhorst
>> <maarten.lankhorst@...ux.intel.com>; Klymenko, Anatoliy
>> <Anatoliy.Klymenko@....com>; Maxime Ripard <mripard@...nel.org>; linux-
>> arm-kernel@...ts.infradead.org; Simona Vetter <simona@...ll.ch>; Simek,
>> Michal <michal.simek@....com>; Sean Anderson
>> <sean.anderson@...ux.dev>
>> Subject: [PATCH 3/3] drm: zynqmp: Add blend mode property to graphics plane
>>
>> Caution: This message originated from an External Source. Use proper caution
>> when opening attachments, clicking links, or responding.
>>
>>
>> When global alpha is enabled, per-pixel alpha is ignored. Allow
>> userspace to explicitly specify whether to use per-pixel alpha by
>> exposing it through the blend mode property. I'm not sure whether the
>> per-pixel alpha is pre-multiplied or not [1], but apparently it *must* be
>> pre-multiplied so I guess we have to advertise it.
>>
>> [1] All we get is "The alpha value available with the graphics stream
>>     will define the transparency of the graphics."
>>
>> Signed-off-by: Sean Anderson <sean.anderson@...ux.dev>
>> ---
>>
>>  drivers/gpu/drm/xlnx/zynqmp_kms.c | 24 ++++++++++++++++++++++--
>>  1 file changed, 22 insertions(+), 2 deletions(-)
>>
>> diff --git a/drivers/gpu/drm/xlnx/zynqmp_kms.c
>> b/drivers/gpu/drm/xlnx/zynqmp_kms.c
>> index 456ada9ac003..fa1cfc16db36 100644
>> --- a/drivers/gpu/drm/xlnx/zynqmp_kms.c
>> +++ b/drivers/gpu/drm/xlnx/zynqmp_kms.c
>> @@ -61,6 +61,13 @@ static int zynqmp_dpsub_plane_atomic_check(struct
>> drm_plane *plane,
>>         if (!new_plane_state->crtc)
>>                 return 0;
>>
>> +       if (new_plane_state->pixel_blend_mode !=
>> DRM_MODE_BLEND_PIXEL_NONE &&
>> +           new_plane_state->alpha >> 8 != 0xff) {
>> +               drm_dbg_kms(plane->dev,
>> +                           "Plane alpha must be 1.0 when using pixel alpha\n");
>> +               return -EINVAL;
>> +       }
>> +
>>         crtc_state = drm_atomic_get_crtc_state(state, new_plane_state->crtc);
>>         if (IS_ERR(crtc_state))
>>                 return PTR_ERR(crtc_state);
>> @@ -117,9 +124,13 @@ static void
>> zynqmp_dpsub_plane_atomic_update(struct drm_plane *plane,
>>
>>         zynqmp_disp_layer_update(layer, new_state);
>>
>> -       if (plane->index == ZYNQMP_DPSUB_LAYER_GFX)
>> -               zynqmp_disp_blend_set_global_alpha(dpsub->disp, true,
>> +       if (plane->index == ZYNQMP_DPSUB_LAYER_GFX) {
>> +               bool blend = plane->state->pixel_blend_mode ==
>> +                            DRM_MODE_BLEND_PIXEL_NONE;
>> +
>> +               zynqmp_disp_blend_set_global_alpha(dpsub->disp, blend,
>>                                                    plane->state->alpha >> 8);
>> +       }
>>
>>         /*
>>          * Unconditionally enable the layer, as it may have been disabled
>> @@ -179,9 +190,18 @@ static int zynqmp_dpsub_create_planes(struct
>> zynqmp_dpsub *dpsub)
>>                         return ret;
>>
>>                 if (i == ZYNQMP_DPSUB_LAYER_GFX) {
>> +                       unsigned int blend_modes =
>> +                               BIT(DRM_MODE_BLEND_PIXEL_NONE) |
>> +                               BIT(DRM_MODE_BLEND_PREMULTI);
> 
> | BIT(DRM_MODE_BLEND_COVERAGE) - this is what implemented in the hardware.

Do you have a datasheet (or other) reference?

But in any case, DRM_MODE_BLEND_PREMULTI is mandatory even if we don't support
it. See drm_plane_create_blend_mode_property for details.

--Sean