[Intel-gfx] [PATCH v2 3/5] drm/i915: Introduce DRM_I915_GEM_MMAP_OFFSET

[Bloomfield, Jon]

> -----Original Message-----
> From: Intel-gfx <intel-gfx-bounces at lists.freedesktop.org> On Behalf Of Abdiel
> Janulgue
> Sent: Monday, October 7, 2019 2:19 AM
> To: intel-gfx at lists.freedesktop.org
> Cc: Auld, Matthew <matthew.auld at intel.com>
> Subject: [Intel-gfx] [PATCH v2 3/5] drm/i915: Introduce
> DRM_I915_GEM_MMAP_OFFSET
> 
> This is really just an alias of mmap_gtt. Add a new CPU mmap
> implementation that allows multiple fault handlers that depends on
> the object's backing pages.
> 
> Note that we multiplex mmap_gtt and mmap_offset through the same ioctl,
> and use the zero extending behaviour of drm to differentiate between
> them, when we inspect the flags.
> 
> Signed-off-by: Abdiel Janulgue <abdiel.janulgue at linux.intel.com>
> Signed-off-by: Matthew Auld <matthew.auld at intel.com>
> Cc: Joonas Lahtinen <joonas.lahtinen at linux.intel.com>
> ---
>  drivers/gpu/drm/i915/gem/i915_gem_mman.c      | 36 +++++++++++++++++--
>  .../gpu/drm/i915/gem/i915_gem_object_types.h  |  3 ++
>  drivers/gpu/drm/i915/i915_drv.c               |  2 +-
>  include/uapi/drm/i915_drm.h                   | 28 +++++++++++++++
>  4 files changed, 66 insertions(+), 3 deletions(-)

How does the label 'offset' fit into this API if it's really about multiple fault handlers?
Could do with a much better description here I think. Who would use this, and why, would help a lot.