linux-kernel - Re: [PATCH 5/6] drm: vkms: Prepare `vkms_wb_encoder_atomic

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Message-ID: <fbe3ad70-375e-0f14-dba3-8f2e3f081457@gmail.com>
Date:   Tue, 19 Oct 2021 16:12:42 -0300
From:   Igor Matheus Andrade Torrente <igormtorrente@...il.com>
To:     Thomas Zimmermann <tzimmermann@...e.de>,
        rodrigosiqueiramelo@...il.com, melissa.srw@...il.com
Cc:     hamohammed.sa@...il.com, daniel@...ll.ch, airlied@...ux.ie,
        contact@...rsion.fr, leandro.ribeiro@...labora.com,
        dri-devel@...ts.freedesktop.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH 5/6] drm: vkms: Prepare `vkms_wb_encoder_atomic_check` to
 accept multiple formats

Hi Thomas,

On 10/19/21 4:17 AM, Thomas Zimmermann wrote:
> Hi
> 
> Am 18.10.21 um 21:32 schrieb Igor Matheus Andrade Torrente:
>> Hi Thomas,
>>
>> On 10/18/21 3:06 PM, Thomas Zimmermann wrote:
>>> Hi
>>>
>>> Am 18.10.21 um 19:41 schrieb Igor Matheus Andrade Torrente:
>>>> Hello,
>>>>
>>>> On 10/18/21 7:14 AM, Thomas Zimmermann wrote:
>>>>> Hi
>>>>>
>>>>> Am 05.10.21 um 22:16 schrieb Igor Matheus Andrade Torrente:
>>>>>> Currently, the vkms atomic check only goes through the first
>>>>>> position of
>>>>>> the `vkms_wb_formats` vector.
>>>>>>
>>>>>> This change prepares the atomic_check to check the entire vector.
>>>>>>
>>>>>> Signed-off-by: Igor Matheus Andrade Torrente <igormtorrente@...il.com>
>>>>>> ---
>>>>>>    drivers/gpu/drm/vkms/vkms_writeback.c | 11 ++++++++++-
>>>>>>    1 file changed, 10 insertions(+), 1 deletion(-)
>>>>>>
>>>>>> diff --git a/drivers/gpu/drm/vkms/vkms_writeback.c
>>>>>> b/drivers/gpu/drm/vkms/vkms_writeback.c
>>>>>> index 5a3e12f105dc..56978f499203 100644
>>>>>> --- a/drivers/gpu/drm/vkms/vkms_writeback.c
>>>>>> +++ b/drivers/gpu/drm/vkms/vkms_writeback.c
>>>>>> @@ -30,6 +30,8 @@ static int vkms_wb_encoder_atomic_check(struct
>>>>>> drm_encoder *encoder,
>>>>>>    {
>>>>>>        struct drm_framebuffer *fb;
>>>>>>        const struct drm_display_mode *mode = &crtc_state->mode;
>>>>>> +    bool format_supported = false;
>>>>>> +    int i;
>>>>>>        if (!conn_state->writeback_job ||
>>>>>> !conn_state->writeback_job->fb)
>>>>>>            return 0;
>>>>>> @@ -41,7 +43,14 @@ static int vkms_wb_encoder_atomic_check(struct
>>>>>> drm_encoder *encoder,
>>>>>>            return -EINVAL;
>>>>>>        }
>>>>>> -    if (fb->format->format != vkms_wb_formats[0]) {
>>>>>> +    for (i = 0; i < ARRAY_SIZE(vkms_wb_formats); i++) {
>>>>>> +        if (fb->format->format == vkms_wb_formats[i]) {
>>>>>> +            format_supported = true;
>>>>>> +            break;
>>>>>> +        }
>>>>>> +    }
>>>>>
>>>>> At a minimum, this loop should be in a helper function. But more
>>>>> generally, I'm surprised that this isn't already covered by the
>>>>> DRM's atomic helpers.
>>>>
>>>> Ok, I can wrap it in a new function.
>>>>
>>>> AFAIK the DRM doesn't cover it. But I may be wrong...
>>>
>>> I couldn't find anything either.
>>>
>>> Other drivers do similar format and frambuffer checks. So I guess a
>>> helper could be implemented. All plane's are supposed to call
>>> drm_atomic_helper_check_plane_state() in their atomic_check() code.
>>> You could add a similar helper, say
>>> drm_atomic_helper_check_writeback_encoder_state(), that tests for the
>>> format and maybe other things as well.
>>
>> Do you think this should be done before or after this patch series?
> 
> Just add it as part of this series and use it for vkms. Other drivers
> can adopt it later on. The rcar-du code [1] looks similar to the one in
> vkms. Maybe put the common tests in to the new helper. You can extract
> the list of supported formats from the property blob, I think.
> 

OK, Thanks!

> Best regards
> Thomas
> 
> [1]
> https://elixir.bootlin.com/linux/v5.14.13/source/drivers/gpu/drm/rcar-du/rcar_du_writeback.c#L140
> 
>>
>>>
>>> Best regards
>>> Thomas
>>>
>>>>
>>>>>
>>>>> Best regards
>>>>> Thomas
>>>>>
>>>>>> +
>>>>>> +    if (!format_supported) {
>>>>>>            DRM_DEBUG_KMS("Invalid pixel format %p4cc\n",
>>>>>>                      &fb->format->format);
>>>>>>            return -EINVAL;
>>>>>>
>>>>>
>>>
>>
>> Thanks,
>> Igor Torrente
>