Re: [PATCH 0/3] embed drm_gem_object into radeon_bo

[Thomas Hellstrom <thomas@shipmail.org>]

Hi, Daniel,

My main concerns previously for embedding GEM objects as user-space 
references for TTM has been twofold and implementation specific.

1) The locking has been using global mutexes where local spin- or RCU 
locks have been more appropriate. It looks like this has finally been / 
is finally going to be addressed.

2) The gem object is too specialized for general purpose use:
a) The shmem member has no natural use with TTM except possibly as a 
persistent swap storage, but in an ideal world, TTM would talk to the 
swap cache directly so in the longer term there is no need for the shmem 
object at all.
b) Implementations may want to use other user-space visible objects than 
buffer objects:
For example fence objects or CPU synchronization objects. The common 
traits of / operations on these are user-space visibility, inter-process 
visibility, refcounting and destruction when the relevant file is closed.

Hence a class that provides only the user-space handles, naming (flink), 
refcounting and registering with a file handle would be the best choice 
of a "base" class. Traditional Gem objects could derive from those and 
provide any extra *generic* members needed for buffer objects.

This doesn't really affect your work though. Just some comments on why 
vmwgfx don't use GEM objects by default and how they could be made 
optimal for TTM-aware drivers.

Thanks,
/Thomas


On 11/13/2010 09:57 PM, Daniel Vetter wrote:
> Hi all,
>
> This patch series embeds drm_gem_object into struct radeon_bo and adjusts
> any references. I've decided against embedding the gem stuff into struct
> ttm_bo because
> - vmwgfx doesn't use gem and
> - ttm is used for implementing the memory management, whereas gem provides
>    the userspace interface (I know, there's some overlap there, but that's
>    not really a new problem).
>
> Please review and consider merging for -next.
>
> Yours, Daniel
>
> Daniel Vetter (3):
>    drm/radeon: embed struct drm_gem_object
>    drm/radeon: introduce gem_to_radeon_bo helper
>    drm/radeon: kill radeon_bo->gobj pointer
>
>   drivers/gpu/drm/radeon/atombios_crtc.c      |    8 ++--
>   drivers/gpu/drm/radeon/evergreen_blit_kms.c |    2 +-
>   drivers/gpu/drm/radeon/r600.c               |    2 +-
>   drivers/gpu/drm/radeon/r600_blit_kms.c      |    2 +-
>   drivers/gpu/drm/radeon/radeon.h             |    3 +-
>   drivers/gpu/drm/radeon/radeon_benchmark.c   |    4 +-
>   drivers/gpu/drm/radeon/radeon_cs.c          |    2 +-
>   drivers/gpu/drm/radeon/radeon_device.c      |    4 +-
>   drivers/gpu/drm/radeon/radeon_fb.c          |   10 +++---
>   drivers/gpu/drm/radeon/radeon_gart.c        |    2 +-
>   drivers/gpu/drm/radeon/radeon_gem.c         |   43 ++++++++++++---------------
>   drivers/gpu/drm/radeon/radeon_legacy_crtc.c |    4 +-
>   drivers/gpu/drm/radeon/radeon_object.c      |   24 +++++++--------
>   drivers/gpu/drm/radeon/radeon_object.h      |    2 +-
>   drivers/gpu/drm/radeon/radeon_ring.c        |    4 +-
>   drivers/gpu/drm/radeon/radeon_test.c        |    4 +-
>   drivers/gpu/drm/radeon/radeon_ttm.c         |    2 +-
>   drivers/gpu/drm/radeon/rv770.c              |    2 +-
>   18 files changed, 59 insertions(+), 65 deletions(-)
>
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