Re: [PATCH] drm/msm: Replace custom dumb_map_offset with generic helper

[Dmitry Baryshkov]

On Mon, Dec 15, 2025 at 02:28:50AM +0000, Swaraj Gaikwad wrote:
> The msm driver implements a custom dumb_map_offset callback. This
> implementation acquires the msm_gem_lock, but the underlying
> drm_gem_create_mmap_offset() function is already thread-safe regarding
> the VMA offset manager (it acquires the mgr->vm_lock internally).

Other pieces are using msm_gem_lock() / msm_gem_unlock(), which
translates to dma_resv_lock() / dma_resv_unlock(), so you need to
describe, why it's still safe wrt. that code.

> 
> Switching to the generic drm_gem_dumb_map_offset() helper provides
> several benefits:
> 1. Removes the unnecessary locking overhead (locking leftovers).
> 2. Adds a missing check to reject mapping of imported objects, which is
>    invalid for dumb buffers.
> 3. Allows for the removal of the msm_gem_dumb_map_offset() wrapper and
>    the msm_gem_mmap_offset() helper function.
> 
> The logic from msm_gem_mmap_offset() has been inlined into
> msm_ioctl_gem_info() to maintain functionality without the separate
> helper.
> 
> This addresses the TODO:
> "Documentation/gpu/todo.rst: Remove custom dumb_map_offset implementations"
> 
> Signed-off-by: Swaraj Gaikwad <swarajgaikwad1925@xxxxxxxxx>
> ---
> 
>  Compile-tested only.
> 

-- 
With best wishes
Dmitry