[Linaro-mm-sig] [PATCH] dma-buf: add vmap interface (v2)

[Sumit Semwal]

Hi Dave,

On 17 May 2012 16:01, Dave Airlie <airlied at gmail.com> wrote:
> From: Dave Airlie <airlied at redhat.com>
>
> The main requirement I have for this interface is for scanning out
> using the USB gpu devices. Since these devices have to read the
> framebuffer on updates and linearly compress it, using kmaps
> is a major overhead for every update.
>
> v2: fix warn issues pointed out by Sylwester Nawrocki.
>
> Signed-off-by: Dave Airlie <airlied at redhat.com>
> ---
>  drivers/base/dma-buf.c  |   34 ++++++++++++++++++++++++++++++++++
>  include/linux/dma-buf.h |   14 ++++++++++++++
>  2 files changed, 48 insertions(+), 0 deletions(-)
>
> diff --git a/drivers/base/dma-buf.c b/drivers/base/dma-buf.c
> index 07cbbc6..750f92c 100644
> --- a/drivers/base/dma-buf.c
> +++ b/drivers/base/dma-buf.c
> @@ -406,3 +406,37 @@ void dma_buf_kunmap(struct dma_buf *dmabuf, unsigned long page_num,
>                dmabuf->ops->kunmap(dmabuf, page_num, vaddr);
>  }
>  EXPORT_SYMBOL_GPL(dma_buf_kunmap);
> +
> +/**
> + * dma_buf_vmap - Create virtual mapping for the buffer object into kernel address space. The same restrictions as for vmap and friends apply.
> + * @dma_buf:   [in]    buffer to vmap
> + *
> + * This call may fail due to lack of virtual mapping address space.
> + * These calls are optional in drivers. The intended use for them
> + * is for mapping objects linear in kernel space for high use objects.
> + * Please attempt to use kmap/kunmap before thinking about these interfaces.
> + */
> +void *dma_buf_vmap(struct dma_buf *dmabuf)
> +{
> +       if (WARN_ON(!dmabuf))
> +               return NULL;
> +
> +       if (dmabuf->ops->vmap)
> +               return dmabuf->ops->vmap(dmabuf);
> +       return NULL;
> +}
> +EXPORT_SYMBOL(dma_buf_vmap);
I am afraid we don't yet have a clear consensus on the usage of
EXPORT_SYMBOL - till it is done, I would prefer that we use
EXPORT_SYMBOL_GPL for consistency. Once we reach agreement, we can
change them all in one go if required.
> +
<snip>
-- 
Thanks and regards,
~Sumit.