Re: [PATCH] drm/i915: disable set/get_tiling ioctl on gen12+

["Souza, Jose" <jose.souza@intel.com>]

On Thu, 2019-08-29 at 08:50 +0200, 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@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.

But like Chris said we are not using EOPNOTSUPP in i915,
i915_perf_open_ioctl() and other 2 perf ioctl uses ENOSUPP, should we
convert those to 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
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