[PATCH v2 1/2] drm/prime: reject DMA-BUF attach when get_sg_table is missing

[Thomas Zimmermann]

Hi

Am 02.03.23 um 15:35 schrieb Simon Ser:
> drm_gem_map_dma_buf() requires drm_gem_object_funcs.get_sg_table
> to be implemented, or else WARNs.
> 
> Allow drivers to leave this hook unimplemented to implement purely
> local DMA-BUFs (ie, DMA-BUFs which cannot be imported anywhere
> else but the device which allocated them). In that case, reject
> imports to other devices in drm_gem_map_attach().
> 
> v2: new patch
> 
> Signed-off-by: Simon Ser <contact at emersion.fr>
> Cc: Daniel Vetter <daniel.vetter at ffwll.ch>
> Cc: Thomas Zimmermann <tzimmermann at suse.de>
> Cc: Tian Tao <tiantao6 at hisilicon.com>
> Cc: Maxime Ripard <maxime at cerno.tech>
> Cc: Christian König <christian.koenig at amd.com>
> Cc: Hans de Goede <hdegoede at redhat.com>
> ---
>   drivers/gpu/drm/drm_prime.c | 6 +++++-
>   1 file changed, 5 insertions(+), 1 deletion(-)
> 
> diff --git a/drivers/gpu/drm/drm_prime.c b/drivers/gpu/drm/drm_prime.c
> index f924b8b4ab6b..ab1d21d63a03 100644
> --- a/drivers/gpu/drm/drm_prime.c
> +++ b/drivers/gpu/drm/drm_prime.c
> @@ -544,7 +544,8 @@ int drm_prime_handle_to_fd_ioctl(struct drm_device *dev, void *data,
>    * Optional pinning of buffers is handled at dma-buf attach and detach time in
>    * drm_gem_map_attach() and drm_gem_map_detach(). Backing storage itself is
>    * handled by drm_gem_map_dma_buf() and drm_gem_unmap_dma_buf(), which relies on
> - * &drm_gem_object_funcs.get_sg_table.
> + * &drm_gem_object_funcs.get_sg_table. If &drm_gem_object_funcs.get_sg_table is
> + * unimplemented, exports into another device are rejected.
>    *
>    * For kernel-internal access there's drm_gem_dmabuf_vmap() and
>    * drm_gem_dmabuf_vunmap(). Userspace mmap support is provided by
> @@ -583,6 +584,9 @@ int drm_gem_map_attach(struct dma_buf *dma_buf,
>   {
>   	struct drm_gem_object *obj = dma_buf->priv;
>   
> +	if (!obj->funcs->get_sg_table)
> +		return -EOPNOTSUPP;

-ENOSYS please.

Best regards
Thomas

> +
>   	return drm_gem_pin(obj);
>   }
>   EXPORT_SYMBOL(drm_gem_map_attach);

-- 
Thomas Zimmermann
Graphics Driver Developer
SUSE Software Solutions Germany GmbH
Maxfeldstr. 5, 90409 Nürnberg, Germany
(HRB 36809, AG Nürnberg)
Geschäftsführer: Ivo Totev
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