Re: [PATCH] drm/vc4: Check for valid formats

["Maíra Canal" <mcanal@igalia.com>]

Hi,

On 1/2/23 11:20, Thomas Zimmermann wrote:
> Hi
> 
> Am 02.01.23 um 14:57 schrieb Maíra Canal:
>> Currently, vc4 is not checking valid formats before creating a
>> framebuffer, which is triggering the IGT test
>> igt@kms_addfb_basic@addfb25-bad-modifier to fail, as vc4 accepts
>> to create a framebuffer with an invalid modifier. Therefore, check
>> for valid formats before creating framebuffers on vc4 and vc5 in
>> order to avoid creating framebuffers with invalid formats.
>>
>> Signed-off-by: Maíra Canal <mcanal@igalia.com>
>> ---
>>   drivers/gpu/drm/vc4/vc4_kms.c | 23 ++++++++++++++++++++++-
>>   1 file changed, 22 insertions(+), 1 deletion(-)
>>
>> diff --git a/drivers/gpu/drm/vc4/vc4_kms.c b/drivers/gpu/drm/vc4/vc4_kms.c
>> index 53d9f30460cf..5d1afd66fcc1 100644
>> --- a/drivers/gpu/drm/vc4/vc4_kms.c
>> +++ b/drivers/gpu/drm/vc4/vc4_kms.c
>> @@ -500,6 +500,27 @@ static struct drm_framebuffer *vc4_fb_create(struct drm_device *dev,
>>         mode_cmd = &mode_cmd_local;
>>     }
>>
>> +    if (!drm_any_plane_has_format(dev, mode_cmd->pixel_format,
>> +                      mode_cmd->modifier[0])) {
>> +        drm_dbg_kms(dev, "Unsupported pixel format %p4cc / modifier 0x%llx\n",
>> +                &mode_cmd->pixel_format, mode_cmd->modifier[0]);
>> +        return ERR_PTR(-EINVAL);
>> +    }
> 
> This might be a stupid question, but why doesn't drm_fbgem_fb_create() do this test already? It seems like a no-brainer and *not* testing for the plane formats should be the exception.

I thought the same initially, but then I found this mention on the TODO list [1]. So, it
is not possible to test it on drm_gem_fb_create() because, for non-atomic, checking
drm_any_plane_has_format() is not possible since like the format list for the primary plane
is fake and we'd therefor reject valid formats.

I'm not sure if anything changed since this was written, but that was the reason that I
decided to introduce the check in the driver instead of the API.

[1] https://cgit.freedesktop.org/drm/drm/tree/Documentation/gpu/todo.rst#n279

Best Regards,
- Maíra Canal

> 
> Best regards
> Thomas
> 
>> +
>> +    return drm_gem_fb_create(dev, file_priv, mode_cmd);
>> +}
>> +
>> +static struct drm_framebuffer *vc5_fb_create(struct drm_device *dev,
>> +                         struct drm_file *file_priv,
>> +                         const struct drm_mode_fb_cmd2 *mode_cmd)
>> +{
>> +    if (!drm_any_plane_has_format(dev, mode_cmd->pixel_format,
>> +                      mode_cmd->modifier[0])) {
>> +        drm_dbg_kms(dev, "Unsupported pixel format %p4cc / modifier 0x%llx\n",
>> +                &mode_cmd->pixel_format, mode_cmd->modifier[0]);
>> +        return ERR_PTR(-EINVAL);
>> +    }
>> +
>>     return drm_gem_fb_create(dev, file_priv, mode_cmd);
>>   }
>>
>> @@ -1033,7 +1054,7 @@ static const struct drm_mode_config_funcs vc4_mode_funcs = {
>>   static const struct drm_mode_config_funcs vc5_mode_funcs = {
>>     .atomic_check = vc4_atomic_check,
>>     .atomic_commit = drm_atomic_helper_commit,
>> -    .fb_create = drm_gem_fb_create,
>> +    .fb_create = vc5_fb_create,
>>   };
>>
>>   int vc4_kms_load(struct drm_device *dev)
>> -- 
>> 2.38.1
>>
>