linux-kernel - Re: [PATCH 2/6] drm: Add drm_atomic_helper_buffer_damage_{iter

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Message-ID: <87r0ks5hqu.fsf@minerva.mail-host-address-is-not-set>
Date:   Tue, 14 Nov 2023 19:09:45 +0100
From:   Javier Martinez Canillas <javierm@...hat.com>
To:     Thomas Zimmermann <tzimmermann@...e.de>,
        linux-kernel@...r.kernel.org
Cc:     nerdopolis <bluescreen_avenger@...izon.net>,
        Pekka Paalanen <pekka.paalanen@...labora.com>,
        dri-devel@...ts.freedesktop.org,
        Sima Vetter <daniel.vetter@...ll.ch>,
        Bilal Elmoussaoui <belmouss@...hat.com>,
        Maxime Ripard <mripard@...nel.org>,
        Gerd Hoffmann <kraxel@...hat.com>, stable@...r.kernel.org,
        Erico Nunes <nunes.erico@...il.com>
Subject: Re: [PATCH 2/6] drm: Add
 drm_atomic_helper_buffer_damage_{iter_init,merged}() helpers

Thomas Zimmermann <tzimmermann@...e.de> writes:

> Hi
>
> Am 14.11.23 um 16:58 schrieb Javier Martinez Canillas:
>> Thomas Zimmermann <tzimmermann@...e.de> writes:
>> 
>> Hello Thomas,
>> 
>> Thanks a lot for your feedback.
>> 
>>> Hi
>>>
>>> Am 09.11.23 um 18:24 schrieb Javier Martinez Canillas:
>>>> To be used by drivers that do per-buffer (e.g: virtio-gpu) uploads (rather
>>>> than per-plane uploads), since these type of drivers need to handle buffer
>>>> damages instead of frame damages.
>>>>
>>>> The drm_atomic_helper_buffer_damage_iter_init() has the same logic than
>>>> drm_atomic_helper_damage_iter_init() but it also takes into account if the
>>>> framebuffer attached to plane's state has changed since the last update.
>>>>
>>>> And the drm_atomic_helper_buffer_damage_merged() is just a version of the
>>>> drm_atomic_helper_damage_merged() helper, but it uses the iter_init helper
>>>> that is mentioned above.
>>>>
>>>> Fixes: 01f05940a9a7 ("drm/virtio: Enable fb damage clips property for the primary plane")
>>>> Cc: <stable@...r.kernel.org> # v6.4+
>>>> Reported-by: nerdopolis <bluescreen_avenger@...izon.net>
>>>> Closes: https://bugzilla.kernel.org/show_bug.cgi?id=218115
>>>> Suggested-by: Sima Vetter <daniel.vetter@...ll.ch>
>>>> Signed-off-by: Javier Martinez Canillas <javierm@...hat.com>
>>>> ---
>>>>
>>>>    drivers/gpu/drm/drm_damage_helper.c | 79 ++++++++++++++++++++++++++---
>>>>    include/drm/drm_damage_helper.h     |  7 +++
>>>>    2 files changed, 80 insertions(+), 6 deletions(-)
>>>>
>>>> diff --git a/drivers/gpu/drm/drm_damage_helper.c b/drivers/gpu/drm/drm_damage_helper.c
>>>> index aa2325567918..b72062c9d31c 100644
>>>> --- a/drivers/gpu/drm/drm_damage_helper.c
>>>> +++ b/drivers/gpu/drm/drm_damage_helper.c
>>>> @@ -204,7 +204,8 @@ EXPORT_SYMBOL(drm_atomic_helper_dirtyfb);
>>>>    static void
>>>>    __drm_atomic_helper_damage_iter_init(struct drm_atomic_helper_damage_iter *iter,
>>>>    				     const struct drm_plane_state *old_state,
>>>> -				     const struct drm_plane_state *state)
>>>> +				     const struct drm_plane_state *state,
>>>> +				     bool buffer_damage)
>>>
>>> I think it would be preferable to drop patches one and two and instead
>>> add this parameter directly to drm_atomic_helper_damage_iter_init() and
>>> drm_atomic_helper_damage_merged().  That's a bit of churn, but more
>>> readable code.
>>>
>> 
>> Makes sense. I'll do that in v2.
>
> Instead of modifying these function interfaces, it might be even better 
> to introduce a state flag in struct drm_plane_state that you can modify 
> in the plane's atomic_check helper. Something simple like this:
>
>    if (old_fb != new_fb)
>      plane_state->ignore_damage_clips = true;
>
> in the affected drivers/planes. In drm_atomic_helper_damage_iter_init() 
> you can use it to generate a full update. This avoids the churn and is 
> in line with the overall check/commit design of the DRM framework.
>

Thanks. That indeed seems more aligned with the rest of the DRM framework.

-- 
Best regards,

Javier Martinez Canillas
Core Platforms
Red Hat