dma-buf: add vmap interface (v3)

From: Dave Airlie <airlied@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.

v3: fix compile !CONFIG_DMA_SHARED_BUFFER and add _GPL for now

Signed-off-by: Dave Airlie <airlied@redhat.com>
---
 drivers/base/dma-buf.c  |   34 ++++++++++++++++++++++++++++++++++
 include/linux/dma-buf.h |   14 ++++++++++++++
 2 files changed, 48 insertions(+), 0 deletions(-)

On Fri, May 18, 2012 at 12:44 PM, Dave Airlie <airlied@gmail.com> wrote:
> From: Dave Airlie <airlied@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.
>
> v3: fix compile !CONFIG_DMA_SHARED_BUFFER and add _GPL for now
>
> Signed-off-by: Dave Airlie <airlied@redhat.com>

Reviewed-by: Rob Clark <rob.clark@linaro.org>

> ---
>  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..0d8197e 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_GPL(dma_buf_vmap);
> +
> +/**
> + * dma_buf_vunmap - Unmap a vmap obtained by dma_buf_vmap.
> + * @dma_buf:   [in]    buffer to vmap
> + */
> +void dma_buf_vunmap(struct dma_buf *dmabuf, void *vaddr)
> +{
> +       if (WARN_ON(!dmabuf))
> +               return;
> +
> +       if (dmabuf->ops->vunmap)
> +               dmabuf->ops->vunmap(dmabuf, vaddr);
> +}
> +EXPORT_SYMBOL_GPL(dma_buf_vunmap);
> diff --git a/include/linux/dma-buf.h b/include/linux/dma-buf.h
> index 3efbfc2..d8c2865 100644
> --- a/include/linux/dma-buf.h
> +++ b/include/linux/dma-buf.h
> @@ -92,6 +92,9 @@ struct dma_buf_ops {
>        void (*kunmap_atomic)(struct dma_buf *, unsigned long, void *);
>        void *(*kmap)(struct dma_buf *, unsigned long);
>        void (*kunmap)(struct dma_buf *, unsigned long, void *);
> +
> +       void *(*vmap)(struct dma_buf *);
> +       void (*vunmap)(struct dma_buf *, void *vaddr);
>  };
>
>  /**
> @@ -167,6 +170,9 @@ void *dma_buf_kmap_atomic(struct dma_buf *, unsigned long);
>  void dma_buf_kunmap_atomic(struct dma_buf *, unsigned long, void *);
>  void *dma_buf_kmap(struct dma_buf *, unsigned long);
>  void dma_buf_kunmap(struct dma_buf *, unsigned long, void *);
> +
> +void *dma_buf_vmap(struct dma_buf *);
> +void dma_buf_vunmap(struct dma_buf *, void *vaddr);
>  #else
>
>  static inline struct dma_buf_attachment *dma_buf_attach(struct dma_buf *dmabuf,
> @@ -248,6 +254,14 @@ static inline void dma_buf_kunmap(struct dma_buf *dmabuf,
>                                  unsigned long pnum, void *vaddr)
>  {
>  }
> +
> +static inline void *dma_buf_vmap(struct dma_buf *dmabuf)
> +{
> +}
> +
> +static inline void dma_buf_vunmap(struct dma_buf *dmabuf, void *vaddr)
> +{
> +}
>  #endif /* CONFIG_DMA_SHARED_BUFFER */
>
>  #endif /* __DMA_BUF_H__ */
> --
> 1.7.6
>
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> dri-devel mailing list
> dri-devel@lists.freedesktop.org
> http://lists.freedesktop.org/mailman/listinfo/dri-devel

Hi Dave,

On 19 May 2012 12:48, Rob Clark <rob.clark@linaro.org> wrote:
> On Fri, May 18, 2012 at 12:44 PM, Dave Airlie <airlied@gmail.com> wrote:
>> From: Dave Airlie <airlied@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.

Thanks; rebased and applied to my for-next.

Would you care to write a small documentation patch like we have for
all the other interfaces?
>>
<snip>
Best regards,
~Sumit.