Re: [PATCH v2 3/6] drm/gem: add drm_gem_prime_dma_buf_to_gem() self-import helper

[Matthew Brost <matthew.brost@intel.com>]

On Mon, Oct 12, 2026 at 06:06:15PM -0700, Niranjana Vishwanathapura wrote:
> drm_gem_is_prime_exported_dma_buf() is a bool predicate that open-codes
> the core PRIME self-import check. Its only caller, the shmem importer,
> then repeats the dma_buf->priv lookup and the reference get.
> 
> Replace it with drm_gem_prime_dma_buf_to_gem(), a thin wrapper around
> drm_gem_prime_self_import() that returns the backing GEM object -- with
> a reference taken -- for a core-PRIME self-export, or NULL otherwise.
> This consolidates self-import handling onto drm_gem_prime_self_import()
> and lets drm_gem_shmem_prime_import_no_map() reuse the object directly.
> 
> Unlike the removed predicate, the helper takes a reference on the
> returned object; the sole caller already wanted the referenced object.
> 
> Assisted-by: GitHub-Copilot:claude-opus-4.8

Assisted-by: LLM

I was going to suggest this last rev too as I noticed
drm_gem_shmem_prime_import_no_map called
drm_gem_is_prime_exported_dma_buf which should prefer the new helper but
shmem couldn't look at drm_gem_prime_dmabuf_ops.

This is a good cleanup:

Reviewed-by: Matthew Brost <matthew.brost@intel.com>

> Signed-off-by: Niranjana Vishwanathapura <niranjana.vishwanathapura@intel.com>
> ---
>  drivers/gpu/drm/drm_gem_shmem_helper.c | 14 ++++++--------
>  drivers/gpu/drm/drm_prime.c            | 26 +++++++++++++++-----------
>  include/drm/drm_prime.h                |  4 ++--
>  3 files changed, 23 insertions(+), 21 deletions(-)
> 
> diff --git a/drivers/gpu/drm/drm_gem_shmem_helper.c b/drivers/gpu/drm/drm_gem_shmem_helper.c
> index d654a22a30de..a0e161f2333e 100644
> --- a/drivers/gpu/drm/drm_gem_shmem_helper.c
> +++ b/drivers/gpu/drm/drm_gem_shmem_helper.c
> @@ -954,15 +954,13 @@ struct drm_gem_object *drm_gem_shmem_prime_import_no_map(struct drm_device *dev,
>  	size_t size;
>  	int ret;
>  
> -	if (drm_gem_is_prime_exported_dma_buf(dev, dma_buf)) {
> -		/*
> -		 * Importing dmabuf exported from our own gem increases
> -		 * refcount on gem itself instead of f_count of dmabuf.
> -		 */
> -		obj = dma_buf->priv;
> -		drm_gem_object_get(obj);
> +	/*
> +	 * Importing a dmabuf exported from our own gem increases the refcount
> +	 * on the gem itself instead of the f_count of the dmabuf.
> +	 */
> +	obj = drm_gem_prime_dma_buf_to_gem(dev, dma_buf);
> +	if (obj)
>  		return obj;
> -	}
>  
>  	attach = dma_buf_attach(dma_buf, dev->dev);
>  	if (IS_ERR(attach))
> diff --git a/drivers/gpu/drm/drm_prime.c b/drivers/gpu/drm/drm_prime.c
> index 588910c250b8..275c5661528d 100644
> --- a/drivers/gpu/drm/drm_prime.c
> +++ b/drivers/gpu/drm/drm_prime.c
> @@ -933,23 +933,27 @@ EXPORT_SYMBOL(drm_gem_prime_export);
>  
>  
>  /**
> - * drm_gem_is_prime_exported_dma_buf -
> - * checks if the DMA-BUF was exported from a GEM object belonging to @dev.
> + * drm_gem_prime_dma_buf_to_gem - GEM object backing a self-exported PRIME dma-buf
>   * @dev: drm_device to check against
>   * @dma_buf: dma-buf object to import
>   *
> - * Return: true if the DMA-BUF was exported from a GEM object belonging
> - * to @dev, false otherwise.
> + * If @dma_buf is a PRIME export of a GEM object that belongs to @dev and uses
> + * the core PRIME dma-buf ops, return that GEM object with an extra reference
> + * taken, so a self-import reuses the GEM object instead of referencing the
> + * dma-buf file. Returns NULL for a foreign dma-buf or one using driver-private
> + * ops; such drivers call drm_gem_prime_self_import() with their own ops.
> + *
> + * The returned object carries a reference the caller must drop with
> + * drm_gem_object_put().
> + *
> + * Return: the referenced GEM object on self-import, or NULL otherwise.
>   */
> -
> -bool drm_gem_is_prime_exported_dma_buf(struct drm_device *dev,
> -				       struct dma_buf *dma_buf)
> +struct drm_gem_object *drm_gem_prime_dma_buf_to_gem(struct drm_device *dev,
> +						    struct dma_buf *dma_buf)
>  {
> -	struct drm_gem_object *obj = dma_buf->priv;
> -
> -	return (dma_buf->ops == &drm_gem_prime_dmabuf_ops) && (obj->dev == dev);
> +	return drm_gem_prime_self_import(dev, dma_buf, &drm_gem_prime_dmabuf_ops);
>  }
> -EXPORT_SYMBOL(drm_gem_is_prime_exported_dma_buf);
> +EXPORT_SYMBOL(drm_gem_prime_dma_buf_to_gem);
>  
>  /**
>   * drm_gem_prime_import_dev - core implementation of the import callback
> diff --git a/include/drm/drm_prime.h b/include/drm/drm_prime.h
> index d378404f8ab4..02665205aed1 100644
> --- a/include/drm/drm_prime.h
> +++ b/include/drm/drm_prime.h
> @@ -101,8 +101,8 @@ struct dma_buf *drm_gem_prime_export(struct drm_gem_object *obj,
>  unsigned long drm_prime_get_contiguous_size(struct sg_table *sgt);
>  
>  /* helper functions for importing */
> -bool drm_gem_is_prime_exported_dma_buf(struct drm_device *dev,
> -				       struct dma_buf *dma_buf);
> +struct drm_gem_object *drm_gem_prime_dma_buf_to_gem(struct drm_device *dev,
> +						    struct dma_buf *dma_buf);
>  
>  struct drm_gem_object *drm_gem_prime_import_dev(struct drm_device *dev,
>  						struct dma_buf *dma_buf,
> -- 
> 2.43.0
>