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

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Date:   Mon, 18 Oct 2021 16:32:40 -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 10/18/21 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?

> 
> 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