dma-buf: add vmap interface (v3)

From: Dave Airlie <[email protected]>

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 <[email protected]>

---
 drivers/base/dma-buf.c  |   34 ++++++++++++++++++++++++++++++++++ include/linux/dma-buf.h |   14 ++++++++++++++

 2 files changed, 48 insertions(+), 0 deletions(-)

drivers/base/dma-buf.c +34 -0

index 07cbbc6..0d8197e 100644
@@ -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);

include/linux/dma-buf.h +14 -1

index 3efbfc2..d8c2865 100644
@@ -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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Quoted 6 lines · Dave Airlie

From: Dave Airlie <[email protected]>

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.

Quoted 1 line