[Intel-gfx] [RFC PATCH 2/2] drm/i915: Account for platform without mappable aperture when returning size

[Chris Wilson]

Quoting Antonio Argenziano (2019-03-07 19:11:15)
> Some devices will not expose a mappable aperture anymore so we need to
> return an appropriate value in that case.
> 
> Signed-off-by: Antonio Argenziano <antonio.argenziano at intel.com>
> 
> Cc: Matthew Auld <matthew.auld at intel.com>
> Cc: Daniele Ceraolo Spurio <daniele.ceraolospurio at intel.com>
> Cc: Chris Wilson <chris at chris-wilson.co.uk>
> ---
>  drivers/gpu/drm/i915/i915_gem.c | 3 ++-
>  1 file changed, 2 insertions(+), 1 deletion(-)
> 
> diff --git a/drivers/gpu/drm/i915/i915_gem.c b/drivers/gpu/drm/i915/i915_gem.c
> index d109f6dbe992..5125a5329100 100644
> --- a/drivers/gpu/drm/i915/i915_gem.c
> +++ b/drivers/gpu/drm/i915/i915_gem.c
> @@ -221,7 +221,8 @@ i915_gem_get_aperture_ioctl(struct drm_device *dev, void *data,
>         args->aper_size = ggtt->vm.total;
>         args->aper_available_size = args->aper_size - pinned;
>  
> -       args->mappable_aperture_size = ggtt->mappable_end;
> +       args->mappable_aperture_size =
> +                       HAS_MAPPABLE_APERTURE(to_i915(dev)) ? ggtt->mappable_end : (__u64)-ENODEV;

Looking above, args->aper_size will also be 0 so that'll be a good clue
for ENODEV. So maybe we can get away with the ambiguous 0 here as we can
use aper_size to differentiate the classes of HW.
-Chris