Re: [PATCH v2 0/6] drm: consolidate self-imported PRIME dma-buf detection

[Niranjana Vishwanathapura <niranjana.vishwanathapura@intel.com>]

On Wed, Oct 14, 2026 at 09:31:00AM +0200, Thomas Zimmermann wrote:
>Hi
>
>Am 13.10.26 um 20:29 schrieb Niranjana Vishwanathapura:
>>On Tue, Oct 13, 2026 at 09:17:17AM +0200, Thomas Zimmermann wrote:
>>>Hi,
>>>
>>>I don't think we should merge this series.
>>>
>>>Testing for the functions struct is a hack, which we do because it 
>>>works in practice. We don't any other good identifier for the 
>>>source of the imported dma_buf. We want to hide this from the 
>>>outside world as much as possible. Putting it into an exported 
>>>interface goes in the wrong direction.
>>>
>>
>>Ok, I understand. Given it is just a utility function that is helpful
>>across drivers, would defining drm_gem_prime_self_import() as a static
>>inline helper in drm_prime.h is permissible?
>
>It's not about the EXPORT_SYMBOL. Please see my reply to Matthew for 
>details.
>
>I think it would be OK to do something like this in the header file:
>
>static inline bool __drm_gem_is_exported_dma_buf(dev, ops, dma_buf)
>{
>    /* do the prime test here, but with the given ops. */
>}
>
>Double-underscore prefix in symbols means 'implementation detail'. The 
>existing drm_gem_is_prime_exported_dma_buf() can be implemented on 
>top; existing callers should continue to use 
>drm_gem_prime_eported_dma_buf().  Other drivers can use the new helper 
>for the test, as they use the same logic internally.
>

drm_gem_is_prime_exported_dma_buf() do not take object reference.
The code duplicated in multliple drivers take object reference. So, we
need the helper routine to take object reference.

Niranjana

>Best regards
>Thomas
>
>
>>
>>Niranjana
>>
>>>Best regards
>>>Thomas
>>>
>>>
>>>Am 13.10.26 um 03:06 schrieb Niranjana Vishwanathapura:
>>>>Detecting that a PRIME dma-buf being imported was exported by the same
>>>>DRM device is a pattern currently open-coded in many drivers (compare
>>>>dma_buf->ops against the driver's own ops, check obj->dev == dev, then
>>>>return the GEM object with an extra reference). This series adds 
>>>>generic
>>>>helpers for it and converts several drivers to use them.
>>>>
>>>>Patch 1 adds drm_gem_prime_self_import(dev, dma_buf, ops): for a 
>>>>dma-buf
>>>>self-exported via the given ops, it returns the backing GEM object with
>>>>a reference, letting a driver short-circuit the generic PRIME 
>>>>import and
>>>>skip the extra dma-buf file reference. Patch 2 converts Xe to it.
>>>>
>>>>Patch 3 adds drm_gem_prime_dma_buf_to_gem(), a thin wrapper that 
>>>>uses the
>>>>core PRIME ops, and replaces the 
>>>>drm_gem_is_prime_exported_dma_buf() bool
>>>>predicate with it so the shmem importer resolves the object directly
>>>>(the sole caller already wanted the referenced object).
>>>>
>>>>Patches 4-6 convert panthor, panfrost and amdgpu to
>>>>drm_gem_prime_self_import(), removing the duplicated open-coded checks.
>>>>
>>>>No intended functional change.
>>>>
>>>>Assisted-by: GitHub-Copilot:claude-opus-4.8
>>>>Signed-off-by: Niranjana Vishwanathapura 
>>>><niranjana.vishwanathapura@intel.com>
>>>>
>>>>Farah Kassabri (2):
>>>>  drm/gem: add helper to detect self-imported PRIME dma-bufs
>>>>  drm/xe/dma-buf: Use drm helper to detect dma-buf self-import
>>>>
>>>>Niranjana Vishwanathapura (4):
>>>>  drm/gem: add drm_gem_prime_dma_buf_to_gem() self-import helper
>>>>  drm/panthor: use drm_gem_prime_self_import() helper
>>>>  drm/panfrost: use drm_gem_prime_self_import() helper
>>>>  drm/amdgpu: use drm_gem_prime_self_import() helper
>>>>
>>>> drivers/gpu/drm/amd/amdgpu/amdgpu_dma_buf.c | 14 +---
>>>> drivers/gpu/drm/drm_gem_shmem_helper.c      | 14 ++--
>>>> drivers/gpu/drm/drm_prime.c                 | 74 +++++++++++++++------
>>>> drivers/gpu/drm/panfrost/panfrost_gem.c     | 10 +--
>>>> drivers/gpu/drm/panthor/panthor_gem.c       | 10 +--
>>>> drivers/gpu/drm/xe/xe_dma_buf.c             | 23 ++++---
>>>> drivers/gpu/drm/xe/xe_dma_buf.h             |  2 +
>>>> include/drm/drm_prime.h                     |  8 ++-
>>>> 8 files changed, 91 insertions(+), 64 deletions(-)
>>>>
>>>
>>>-- 
>>>-- 
>>>Thomas Zimmermann
>>>Graphics Driver Developer
>>>SUSE Software Solutions Germany GmbH
>>>Frankenstr. 146, 90461 Nürnberg, Germany, www.suse.com
>>>GF: Stefan Gaiser, Jochen Jaser, Abhinav Puri, (HRB 36809, AG Nürnberg)
>>>
>>>
>
>-- 
>--
>Thomas Zimmermann
>Graphics Driver Developer
>SUSE Software Solutions Germany GmbH
>Frankenstr. 146, 90461 Nürnberg, Germany, www.suse.com
>GF: Stefan Gaiser, Jochen Jaser, Abhinav Puri, (HRB 36809, AG Nürnberg)
>
>