[Linaro-mm-sig] [PATCH] dma-buf: add initial vmap documentation

[Chris Wilson]

On Tue, 22 May 2012 13:34:38 +0100, Dave Airlie <airlied at gmail.com> wrote:
> From: Dave Airlie <airlied at redhat.com>

Inline comment for one sentence that made no sense.

> Signed-off-by: Dave Airlie <airlied at redhat.com>
> ---
>  Documentation/dma-buf-sharing.txt |   11 +++++++++++
>  1 files changed, 11 insertions(+), 0 deletions(-)
> 
> diff --git a/Documentation/dma-buf-sharing.txt b/Documentation/dma-buf-sharing.txt
> index 3bbd5c5..98e9fa0 100644
> --- a/Documentation/dma-buf-sharing.txt
> +++ b/Documentation/dma-buf-sharing.txt
> @@ -300,6 +300,17 @@ Access to a dma_buf from the kernel context involves three steps:
>     Note that these calls need to always succeed. The exporter needs to complete
>     any preparations that might fail in begin_cpu_access.
>  
> +   For some circumstances the overhead of kmap can be too high, a vmap interface
> +   is introduced. This interface shouldn't be used very carefully, as vmalloc
This interface should be used carefully.

Sparingly would also be appropriate, though in less regular usage than
carefully.

> +   space is a limited resources on many architectures.
> +
> +   Interfaces:
> +      void *dma_buf_vmap(struct dma_buf *dmabuf)
> +      void dma_buf_vunmap(struct dma_buf *dmabuf, void *vaddr)
> +
> +   This call can fail if there is no vmap support in the exporter, or if it
> +   runs out of vmalloc space. Fallback to kmap should be implemented.
> +
>  3. Finish access

-- 
Chris Wilson, Intel Open Source Technology Centre