3 files changed, 253 insertions, 0 deletions

diff --git a/drivers/base/Kconfig b/drivers/base/Kconfig
index a5e6d750b716..dc8d213d9933 100644
--- a/drivers/base/Kconfig
+++ b/drivers/base/Kconfig
@@ -253,4 +253,14 @@ config CMA_ALIGNMENT
 
 endif
 
+config DMA_SHARED_BUFFER
+	bool "Buffer framework to be shared between drivers"
+	default n
+	depends on ANON_INODES
+	help
+	  This option enables the framework for buffer-sharing between
+	  multiple drivers. A buffer is associated with a file using driver
+	  APIs extension; the file's descriptor can then be passed on to other
+	  driver.
+
 endmenu
diff --git a/drivers/base/Makefile b/drivers/base/Makefile
index 794546f18406..8c57b68cc459 100644
--- a/drivers/base/Makefile
+++ b/drivers/base/Makefile
@@ -9,6 +9,7 @@ obj-$(CONFIG_CMA) += dma-contiguous.o
 obj-y			+= power/
 obj-$(CONFIG_HAS_DMA)	+= dma-mapping.o
 obj-$(CONFIG_HAVE_GENERIC_DMA_COHERENT) += dma-coherent.o
+obj-$(CONFIG_DMA_SHARED_BUFFER) += dma-buf.o
 obj-$(CONFIG_ISA)	+= isa.o
 obj-$(CONFIG_FW_LOADER)	+= firmware_class.o
 obj-$(CONFIG_NUMA)	+= node.o
diff --git a/drivers/base/dma-buf.c b/drivers/base/dma-buf.c
new file mode 100644
index 000000000000..58c51a03309f
--- /dev/null
+++ b/drivers/base/dma-buf.c
@@ -0,0 +1,242 @@
+/*
+ * Framework for buffer objects that can be shared across devices/subsystems.
+ *
+ * Copyright(C) 2011 Linaro Limited. All rights reserved.
+ * Author: Sumit Semwal <sumit.semwal@ti.com>
+ *
+ * Many thanks to linaro-mm-sig list, and specially
+ * Arnd Bergmann <arnd@arndb.de>, Rob Clark <rob@ti.com> and
+ * Daniel Vetter <daniel@ffwll.ch> for their support in creation and
+ * refining of this idea.
+ *
+ * This program is free software; you can redistribute it and/or modify it
+ * under the terms of the GNU General Public License version 2 as published by
+ * the Free Software Foundation.
+ *
+ * This program is distributed in the hope that it will be useful, but WITHOUT
+ * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
+ * FITNESS FOR A PARTICULAR PURPOSE.  See the GNU General Public License for
+ * more details.
+ *
+ * You should have received a copy of the GNU General Public License along with
+ * this program.  If not, see <http://www.gnu.org/licenses/>.
+ */
+
+#include <linux/fs.h>
+#include <linux/slab.h>
+#include <linux/dma-buf.h>
+#include <linux/anon_inodes.h>
+
+static inline int is_dma_buf_file(struct file *);
+
+static int dma_buf_mmap(struct file *file, struct vm_area_struct *vma)
+{
+	struct dma_buf *dmabuf;
+
+	if (!is_dma_buf_file(file))
+		return -EINVAL;
+
+	dmabuf = file->private_data;
+
+	if (!dmabuf->ops->mmap)
+		return -EINVAL;
+
+	return dmabuf->ops->mmap(dmabuf, vma);
+}
+
+static int dma_buf_release(struct inode *inode, struct file *file)
+{
+	struct dma_buf *dmabuf;
+
+	if (!is_dma_buf_file(file))
+		return -EINVAL;
+
+	dmabuf = file->private_data;
+
+	dmabuf->ops->release(dmabuf);
+	kfree(dmabuf);
+	return 0;
+}
+
+static const struct file_operations dma_buf_fops = {
+	.mmap		= dma_buf_mmap,
+	.release	= dma_buf_release,
+};
+
+/*
+ * is_dma_buf_file - Check if struct file* is associated with dma_buf
+ */
+static inline int is_dma_buf_file(struct file *file)
+{
+	return file->f_op == &dma_buf_fops;
+}
+
+/**
+ * dma_buf_export - Creates a new dma_buf, and associates an anon file
+ * with this buffer,so it can be exported.
+ * Also connect the allocator specific data and ops to the buffer.
+ *
+ * @priv:	[in]	Attach private data of allocator to this buffer
+ * @ops:	[in]	Attach allocator-defined dma buf ops to the new buffer.
+ * @flags:	[in]	mode flags for the file.
+ *
+ * Returns, on success, a newly created dma_buf object, which wraps the
+ * supplied private data and operations for dma_buf_ops. On failure to
+ * allocate the dma_buf object, it can return NULL.
+ *
+ */
+struct dma_buf *dma_buf_export(void *priv, struct dma_buf_ops *ops,
+				int flags)
+{
+	struct dma_buf *dmabuf;
+	struct file *file;
+
+	BUG_ON(!priv || !ops);
+
+	dmabuf = kzalloc(sizeof(struct dma_buf), GFP_KERNEL);
+	if (dmabuf == NULL)
+		return dmabuf;
+
+	dmabuf->priv = priv;
+	dmabuf->ops = ops;
+
+	file = anon_inode_getfile("dmabuf", &dma_buf_fops, dmabuf, flags);
+
+	dmabuf->file = file;
+
+	mutex_init(&dmabuf->lock);
+	INIT_LIST_HEAD(&dmabuf->attachments);
+
+	return dmabuf;
+}
+EXPORT_SYMBOL(dma_buf_export);
+
+
+/**
+ * dma_buf_fd - returns a file descriptor for the given dma_buf
+ * @dmabuf:	[in]	pointer to dma_buf for which fd is required.
+ *
+ * On success, returns an associated 'fd'. Else, returns error.
+ */
+int dma_buf_fd(struct dma_buf *dmabuf)
+{
+	int error, fd;
+
+	if (!dmabuf->file)
+		return -EINVAL;
+
+	error = get_unused_fd_flags(0);
+	if (error < 0)
+		return error;
+	fd = error;
+
+	fd_install(fd, dmabuf->file);
+
+	return fd;
+}
+EXPORT_SYMBOL(dma_buf_fd);
+
+/**
+ * dma_buf_get - returns the dma_buf structure related to an fd
+ * @fd:	[in]	fd associated with the dma_buf to be returned
+ *
+ * On success, returns the dma_buf structure associated with an fd; uses
+ * file's refcounting done by fget to increase refcount. returns ERR_PTR
+ * otherwise.
+ */
+struct dma_buf *dma_buf_get(int fd)
+{
+	struct file *file;
+
+	file = fget(fd);
+
+	if (!file)
+		return ERR_PTR(-EBADF);
+
+	if (!is_dma_buf_file(file)) {
+		fput(file);
+		return ERR_PTR(-EINVAL);
+	}
+
+	return file->private_data;
+}
+EXPORT_SYMBOL(dma_buf_get);
+
+/**
+ * dma_buf_put - decreases refcount of the buffer
+ * @dmabuf:	[in]	buffer to reduce refcount of
+ *
+ * Uses file's refcounting done implicitly by fput()
+ */
+void dma_buf_put(struct dma_buf *dmabuf)
+{
+	BUG_ON(!dmabuf->file);
+
+	fput(dmabuf->file);
+
+	return;
+}
+EXPORT_SYMBOL(dma_buf_put);
+
+/**
+ * dma_buf_attach - Add the device to dma_buf's attachments list; optionally,
+ * calls attach() of dma_buf_ops to allow device-specific attach functionality
+ * @dmabuf:	[in]	buffer to attach device to.
+ * @dev:	[in]	device to be attached.
+ *
+ * Returns struct dma_buf_attachment * for this attachment; may return NULL.
+ *
+ */
+struct dma_buf_attachment *dma_buf_attach(struct dma_buf *dmabuf,
+						struct device *dev)
+{
+	struct dma_buf_attachment *attach;
+	int ret;
+
+	BUG_ON(!dmabuf || !dev);
+
+	mutex_lock(&dmabuf->lock);
+
+	attach = kzalloc(sizeof(struct dma_buf_attachment), GFP_KERNEL);
+	if (attach == NULL)
+		goto err_alloc;
+
+	attach->dev = dev;
+	if (dmabuf->ops->attach) {
+		ret = dmabuf->ops->attach(dmabuf, dev, attach);
+		if (!ret)
+			goto err_attach;
+	}
+	list_add(&attach->node, &dmabuf->attachments);
+
+err_alloc:
+	mutex_unlock(&dmabuf->lock);
+	return attach;
+err_attach:
+	kfree(attach);
+	mutex_unlock(&dmabuf->lock);
+	return ERR_PTR(ret);
+}
+EXPORT_SYMBOL(dma_buf_attach);
+
+/**
+ * dma_buf_detach - Remove the given attachment from dmabuf's attachments list;
+ * optionally calls detach() of dma_buf_ops for device-specific detach
+ * @dmabuf:	[in]	buffer to detach from.
+ * @attach:	[in]	attachment to be detached; is free'd after this call.
+ *
+ */
+void dma_buf_detach(struct dma_buf *dmabuf, struct dma_buf_attachment *attach)
+{
+	BUG_ON(!dmabuf || !attach);
+
+	mutex_lock(&dmabuf->lock);
+	list_del(&attach->node);
+	if (dmabuf->ops->detach)
+		dmabuf->ops->detach(dmabuf, attach);
+
+	kfree(attach);
+	mutex_unlock(&dmabuf->lock);
+	return;
+}
+EXPORT_SYMBOL(dma_buf_detach);