[PATCH] drm/gem-cma-helper: Change the level of the allocation failure message

[Daniel Vetter]

On Wed, Oct 04, 2017 at 03:08:39PM +0200, Boris Brezillon wrote:
> drm_gem_cma_create() prints an error message when dma_alloc_wc() fails to
> allocate the amount of memory we requested. This can lead to annoying
> error messages when CMA is only one possible source of memory for the BO
> allocation.
> 
> Turn this error message into a debug one and add a __must_check specifier
> to make sure all callers are checking the return value.
> 
> Signed-off-by: Boris Brezillon <boris.brezillon at free-electrons.com>

Assuming gcc doesn't spot any driver that now stumbles over the
__must_check:

Reviewed-by: Daniel Vetter <daniel.vetter at ffwll.ch>

Would be good to get Laurent's ack too.
-Daniel

> ---
> Hello,
> 
> This problem happens with the VC4 driver which can flush its internal
> cache if case of CMA allocation failures. We should only complain if the
> last CMA allocation fails (the one happening after all internal caches
> have been flushed).
> 
> Regards,
> 
> Boris
> ---
>  drivers/gpu/drm/drm_gem_cma_helper.c | 4 ++--
>  include/drm/drm_gem_cma_helper.h     | 4 ++--
>  2 files changed, 4 insertions(+), 4 deletions(-)
> 
> diff --git a/drivers/gpu/drm/drm_gem_cma_helper.c b/drivers/gpu/drm/drm_gem_cma_helper.c
> index 373e33f22be4..e96c95c4fd23 100644
> --- a/drivers/gpu/drm/drm_gem_cma_helper.c
> +++ b/drivers/gpu/drm/drm_gem_cma_helper.c
> @@ -95,7 +95,7 @@ __drm_gem_cma_create(struct drm_device *drm, size_t size)
>   *
>   * Returns:
>   * A struct drm_gem_cma_object * on success or an ERR_PTR()-encoded negative
> - * error code on failure.
> + * error code on failure. Callers must check the return value.
>   */
>  struct drm_gem_cma_object *drm_gem_cma_create(struct drm_device *drm,
>  					      size_t size)
> @@ -112,7 +112,7 @@ struct drm_gem_cma_object *drm_gem_cma_create(struct drm_device *drm,
>  	cma_obj->vaddr = dma_alloc_wc(drm->dev, size, &cma_obj->paddr,
>  				      GFP_KERNEL | __GFP_NOWARN);
>  	if (!cma_obj->vaddr) {
> -		dev_err(drm->dev, "failed to allocate buffer with size %zu\n",
> +		dev_dbg(drm->dev, "failed to allocate buffer with size %zu\n",
>  			size);
>  		ret = -ENOMEM;
>  		goto error;
> diff --git a/include/drm/drm_gem_cma_helper.h b/include/drm/drm_gem_cma_helper.h
> index 58a739bf15f1..1b7d938a31a0 100644
> --- a/include/drm/drm_gem_cma_helper.h
> +++ b/include/drm/drm_gem_cma_helper.h
> @@ -77,8 +77,8 @@ int drm_gem_cma_dumb_create(struct drm_file *file_priv,
>  int drm_gem_cma_mmap(struct file *filp, struct vm_area_struct *vma);
>  
>  /* allocate physical memory */
> -struct drm_gem_cma_object *drm_gem_cma_create(struct drm_device *drm,
> -					      size_t size);
> +struct drm_gem_cma_object *
> +__must_check drm_gem_cma_create(struct drm_device *drm, size_t size);
>  
>  extern const struct vm_operations_struct drm_gem_cma_vm_ops;
>  
> -- 
> 2.11.0
> 

-- 
Daniel Vetter
Software Engineer, Intel Corporation
http://blog.ffwll.ch