[Intel-gfx] [RFC] drm/i915: Restrict legacy color key ioctl to pre-gen12

[Ville Syrjälä]

On Tue, Jan 14, 2020 at 02:45:08PM -0800, Matt Roper wrote:
> Since gen12 platform support isn't finalized yet, let's kill off the
> legacy color key ioctl for this platform; there's no userspace today
> that can run on this platform that utilizes this legacy ioctl, so we can
> safely kill it now before it becomes ABI.
> 
> Color key functionality never got integrated into the property / atomic
> interface, and the only known open source consumer was the Intel DDX
> which was never updated to run on platforms beyond gen9.  If color
> keying is desired going forward, it should really be exposed as a
> property so that it can be applied atomically with other display updates
> (and should probably be standardized in a way all drivers can choose to
> support rather than being i915-specific).
> 
> Arguably we might be able to prohibit this on gen10 and gen11 as well
> since no open source userspace exists for those platforms that utilizes
> these ioctls.  However there's always the very slight chance that
> unknown closed source software is actively utilizing the color key ioctl
> on those platforms, so we should maintain the support there to avoid
> breaking ABI.

Can't really see much point in this. The hardware hasn't changed so
arbitrarily cutting this off won't simplify anything.

> 
> Cc: Ville Syrjälä <ville.syrjala at linux.intel.com>
> Cc: Chris Wilson <chris at chris-wilson.co.uk>
> Cc: Daniel Vetter <daniel at ffwll.ch>
> Signed-off-by: Matt Roper <matthew.d.roper at intel.com>
> ---
>  drivers/gpu/drm/i915/display/intel_sprite.c | 8 ++++++++
>  1 file changed, 8 insertions(+)
> 
> diff --git a/drivers/gpu/drm/i915/display/intel_sprite.c b/drivers/gpu/drm/i915/display/intel_sprite.c
> index fca77ec1e0dd..6e8a4686a406 100644
> --- a/drivers/gpu/drm/i915/display/intel_sprite.c
> +++ b/drivers/gpu/drm/i915/display/intel_sprite.c
> @@ -2290,6 +2290,14 @@ int intel_sprite_set_colorkey_ioctl(struct drm_device *dev, void *data,
>  	struct drm_modeset_acquire_ctx ctx;
>  	int ret = 0;
>  
> +	/*
> +	 * Userspace that uses this legacy interface only exists up through
> +	 * gen9.  Discontinue support for the interface starting with gen12 so
> +	 * that it doesn't become ABI on newer platforms.
> +	 */
> +	if (INTEL_GEN(dev_priv) >= 12)
> +		return -EINVAL;
> +
>  	/* ignore the pointless "none" flag */
>  	set->flags &= ~I915_SET_COLORKEY_NONE;
>  
> -- 
> 2.23.0

-- 
Ville Syrjälä
Intel