[PATCH 3/3] drm/i915: Use CPU mapping for userspace dma-buf mmap()

[Chris Wilson]

On Wed, Aug 05, 2015 at 07:13:11PM -0300, Tiago Vignatti wrote:
> Userspace is the one in charge of flush CPU by wrapping mmap with
> begin{,end}_cpu_access.
> 
> v2: Remove LLC check cause we have dma-buf sync providers now. Also, fix return
> before transferring ownership when mmap fails.

i915 doesn't implement end_cpu_access() as required for your sync ioctl.
 
> Signed-off-by: Tiago Vignatti <tiago.vignatti at intel.com>
> ---
>  drivers/gpu/drm/i915/i915_gem_dmabuf.c | 18 +++++++++++++++++-
>  1 file changed, 17 insertions(+), 1 deletion(-)
> 
> diff --git a/drivers/gpu/drm/i915/i915_gem_dmabuf.c b/drivers/gpu/drm/i915/i915_gem_dmabuf.c
> index e9c2bfd..b608f67 100644
> --- a/drivers/gpu/drm/i915/i915_gem_dmabuf.c
> +++ b/drivers/gpu/drm/i915/i915_gem_dmabuf.c
> @@ -193,7 +193,23 @@ static void i915_gem_dmabuf_kunmap(struct dma_buf *dma_buf, unsigned long page_n
>  
>  static int i915_gem_dmabuf_mmap(struct dma_buf *dma_buf, struct vm_area_struct *vma)
>  {
> -	return -EINVAL;
> +	struct drm_i915_gem_object *obj = dma_buf_to_obj(dma_buf);
> +	int ret;
> +
> +	if (obj->base.size < vma->vm_end - vma->vm_start)
> +		return -EINVAL;
> +
> +	if (WARN_ON(!obj->base.filp))
> +		return -EINVAL;

So long as Linus is not watching, ENODEV - since we could support it,
but we just have not implemented it yet.

> +	ret = obj->base.filp->f_op->mmap(obj->base.filp, vma);
> +	if (IS_ERR_VALUE(ret))
> +		return -EINVAL;

The return is 0 on success or error otherwise. Always propagate the
original error unless you have good reason not to (in which case you
document it). So

if (ret)
  return ret;

> +
> +	fput(vma->vm_file);
> +	vma->vm_file = get_file(obj->base.filp);
> +
> +	return ret;

return 0;

>  }
>  
>  static int i915_gem_begin_cpu_access(struct dma_buf *dma_buf, size_t start, size_t length, enum dma_data_direction direction)
> -- 
> 2.1.0
> 

-- 
Chris Wilson, Intel Open Source Technology Centre