linux-kernel - Re: [PATCH v1 1/2] drm/amdgpu: make non-NULL out fence mandatory

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Message-ID: <f66cc34f-b54b-4f91-a6fe-11a146c516b2@amd.com>
Date: Tue, 16 Sep 2025 11:25:06 +0200
From: Christian König <christian.koenig@....com>
To: Pierre-Eric Pelloux-Prayer <pierre-eric.pelloux-prayer@....com>,
 Alex Deucher <alexander.deucher@....com>, David Airlie <airlied@...il.com>,
 Simona Vetter <simona@...ll.ch>, Sumit Semwal <sumit.semwal@...aro.org>
Cc: amd-gfx@...ts.freedesktop.org, dri-devel@...ts.freedesktop.org,
 linux-kernel@...r.kernel.org, linux-media@...r.kernel.org,
 linaro-mm-sig@...ts.linaro.org
Subject: Re: [PATCH v1 1/2] drm/amdgpu: make non-NULL out fence mandatory

On 16.09.25 09:08, Pierre-Eric Pelloux-Prayer wrote:
> amdgpu_ttm_copy_mem_to_mem has a single caller, make sure the out
> fence is non-NULL to simplify the code.
> Since none of the pointers should be NULL, we can enable
> __attribute__((nonnull))__.
> 
> While at it make the function static since it's only used from
> amdgpuu_ttm.c.
> 
> Signed-off-by: Pierre-Eric Pelloux-Prayer <pierre-eric.pelloux-prayer@....com>
> ---
>  drivers/gpu/drm/amd/amdgpu/amdgpu_ttm.c | 17 ++++++++---------
>  drivers/gpu/drm/amd/amdgpu/amdgpu_ttm.h |  6 ------
>  2 files changed, 8 insertions(+), 15 deletions(-)
> 
> diff --git a/drivers/gpu/drm/amd/amdgpu/amdgpu_ttm.c b/drivers/gpu/drm/amd/amdgpu/amdgpu_ttm.c
> index 27ab4e754b2a..70b817b5578d 100644
> --- a/drivers/gpu/drm/amd/amdgpu/amdgpu_ttm.c
> +++ b/drivers/gpu/drm/amd/amdgpu/amdgpu_ttm.c
> @@ -284,12 +284,13 @@ static int amdgpu_ttm_map_buffer(struct ttm_buffer_object *bo,
>   * move and different for a BO to BO copy.
>   *
>   */
> -int amdgpu_ttm_copy_mem_to_mem(struct amdgpu_device *adev,
> -			       const struct amdgpu_copy_mem *src,
> -			       const struct amdgpu_copy_mem *dst,
> -			       uint64_t size, bool tmz,
> -			       struct dma_resv *resv,
> -			       struct dma_fence **f)
> +__attribute__((nonnull))

That looks fishy.

> +static int amdgpu_ttm_copy_mem_to_mem(struct amdgpu_device *adev,
> +				      const struct amdgpu_copy_mem *src,
> +				      const struct amdgpu_copy_mem *dst,
> +				      uint64_t size, bool tmz,
> +				      struct dma_resv *resv,
> +				      struct dma_fence **f)

I'm not an expert for those, but looking at other examples that should be here and look something like:

__attribute__((nonnull(7)))

But I think for this case here it is also not a must have to have that.

Regards,
Christian.

>  {
>  	struct amdgpu_ring *ring = adev->mman.buffer_funcs_ring;
>  	struct amdgpu_res_cursor src_mm, dst_mm;
> @@ -363,9 +364,7 @@ int amdgpu_ttm_copy_mem_to_mem(struct amdgpu_device *adev,
>  	}
>  error:
>  	mutex_unlock(&adev->mman.gtt_window_lock);
> -	if (f)
> -		*f = dma_fence_get(fence);
> -	dma_fence_put(fence);
> +	*f = fence;
>  	return r;
>  }
>  
> diff --git a/drivers/gpu/drm/amd/amdgpu/amdgpu_ttm.h b/drivers/gpu/drm/amd/amdgpu/amdgpu_ttm.h
> index bb17987f0447..07ae2853c77c 100644
> --- a/drivers/gpu/drm/amd/amdgpu/amdgpu_ttm.h
> +++ b/drivers/gpu/drm/amd/amdgpu/amdgpu_ttm.h
> @@ -170,12 +170,6 @@ int amdgpu_copy_buffer(struct amdgpu_ring *ring, uint64_t src_offset,
>  		       struct dma_resv *resv,
>  		       struct dma_fence **fence, bool direct_submit,
>  		       bool vm_needs_flush, uint32_t copy_flags);
> -int amdgpu_ttm_copy_mem_to_mem(struct amdgpu_device *adev,
> -			       const struct amdgpu_copy_mem *src,
> -			       const struct amdgpu_copy_mem *dst,
> -			       uint64_t size, bool tmz,
> -			       struct dma_resv *resv,
> -			       struct dma_fence **f);
>  int amdgpu_ttm_clear_buffer(struct amdgpu_bo *bo,
>  			    struct dma_resv *resv,
>  			    struct dma_fence **fence);