[Intel-gfx] [PATCH] drm/i915: disable set/get_tiling ioctl on gen12+

[Brian Welty]

On 8/28/2019 11:50 PM, Daniel Vetter wrote:
> On Wed, Aug 28, 2019 at 08:31:27PM +0000, Souza, Jose wrote:
>> On Wed, 2019-08-28 at 21:13 +0100, Chris Wilson wrote:
>>> Quoting Souza, Jose (2019-08-28 21:11:53)
>>>> Reviewed-by: José Roberto de Souza <jose.souza at intel.com>
>>>
>>> It's using a non-standard for i915 error code, and get_tiling is not
>>
>> Huum should it use ENOTSUPP then?!
> 
> https://dri.freedesktop.org/docs/drm/gpu/drm-uapi.html#recommended-ioctl-return-values
> 
> Per above "feature not supported" -> EOPNOTSUPP.
> 
>>> affected, it will always return LINEAR. You cannot set tiling as 
>>
>> Following this set_tiling() LINEAR should be allowed too.
>> I prefer the current approach of returning error.
> 
> I'm not seeing the value in keeping get_tiling supported. Either userspace
> still uses the legacy backhannel and dri2, in which case it needs to be
> fixed no matter what. Or it's using modifiers, in which case this is dead
> code. Only other user I can think of is takeover for fastboot, but if you
> get anything else than untiled it's also broken (we don't have an ioctl to
> read out the modifiers, heck even all the planes, there's no getfb2).
> 
> So really not seeing the point in keeping that working.

Daniel,  I came across usage of GET_TILING in libdrm.
Is used in drm_intel_bo_gem_create_from_name() and drm_intel_bo_gem_create_from_prime().
Should these be updated so they don't fail when EOPNOTSUPP is returned on gen12+?
Maybe libdrm should just set tiling_mode to 0 on EOPNOTSUPP error instead of those calls failing?

-Brian