[PATCH 9/9] drm/virtio: Implement dumb_create_fbdev with GEM SHMEM helpers

[Javier Martinez Canillas]

On 3/9/22 09:52, Thomas Zimmermann wrote:

[snip]

>>> +struct drm_gem_object *virtio_gpu_create_object_fbdev(struct drm_device *dev,
>>> +						      size_t size)
>>> +{
>>> +	return ERR_PTR(-ENOSYS);
>>> +}
>>
>> As mentioned, I believe this should be ERR_PTR(-ENOTSUPP) instead.
> 
> I've been wondering about this as well. I finally went with the rules at 
> [1].  All the variants of ENOTOP/ENOTSUPP seem to be for specific use 
> cases, such as a certain feature is not implemented be a specific 
> interface (e.g., sockets for EOPNOTSUPP).  ENOSYS is the only general 
> error that indicates that an entire interface is missing. Even though 
> checkpatch.pl warns that it's only for system calls.
> 
> Best regards
> Thomas
> 
> [1] https://www.cs.helsinki.fi/linux/linux-kernel/2002-30/1135.html
>

Thanks for the link. It would be good to have an authoritative guideline
about this in the kernel documentation (and make checkpatch.pl aware).

-- 
Best regards,

Javier Martinez Canillas
Linux Engineering
Red Hat