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

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Message-ID: <9dbd2c55-2c29-eb12-94d0-dbd5110c302e@suse.de>
Date:   Mon, 18 Oct 2021 20:06:16 +0200
From:   Thomas Zimmermann <tzimmermann@...e.de>
To:     Igor Matheus Andrade Torrente <igormtorrente@...il.com>,
        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,
        lkcamp@...ts.libreplanetbr.org
Subject: Re: [PATCH 5/6] drm: vkms: Prepare `vkms_wb_encoder_atomic_check` to
 accept multiple formats

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.

Best regards
Thomas

> 
>>
>> Best regards
>> Thomas
>>
>>> +
>>> +    if (!format_supported) {
>>>           DRM_DEBUG_KMS("Invalid pixel format %p4cc\n",
>>>                     &fb->format->format);
>>>           return -EINVAL;
>>>
>>

-- 
Thomas Zimmermann
Graphics Driver Developer
SUSE Software Solutions Germany GmbH
Maxfeldstr. 5, 90409 Nürnberg, Germany
(HRB 36809, AG Nürnberg)
Geschäftsführer: Felix Imendörffer

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