[PATCH] dma-buf: add vmap interface (v3)

[Dave Airlie]

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.

v3: fix compile !CONFIG_DMA_SHARED_BUFFER and add _GPL for now

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..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