dma-buf: Introduce dma buffer sharing mechanism

source "drivers/base/regmap/Kconfig"

config DMA_SHARED_BUFFER

	bool "Buffer framework to be shared between drivers"

	default n

	select 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

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

/*

 * 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>

#include <linux/export.h>

static inline int is_dma_buf_file(struct file *);

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 = {

	.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.

 * @size:	[in]	Size of the 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 either missing

 * ops, or error in allocating struct dma_buf, will return negative error.

 *

 */

struct dma_buf *dma_buf_export(void *priv, struct dma_buf_ops *ops,

				size_t size, int flags)

{

	struct dma_buf *dmabuf;

	struct file *file;

	if (WARN_ON(!priv || !ops

			  || !ops->map_dma_buf

			  || !ops->unmap_dma_buf

			  || !ops->release)) {

		return ERR_PTR(-EINVAL);

	}

	dmabuf = kzalloc(sizeof(struct dma_buf), GFP_KERNEL);

	if (dmabuf == NULL)

		return ERR_PTR(-ENOMEM);

	dmabuf->priv = priv;

	dmabuf->ops = ops;

	dmabuf->size = size;

	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_GPL(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 || !dmabuf->file)

		return -EINVAL;

	error = get_unused_fd();

	if (error < 0)

		return error;

	fd = error;

	fd_install(fd, dmabuf->file);

	return fd;

}

EXPORT_SYMBOL_GPL(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_GPL(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)

{

	if (WARN_ON(!dmabuf || !dmabuf->file))

		return;

	fput(dmabuf->file);

}

EXPORT_SYMBOL_GPL(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 negative

 * error codes.

 *

 */

struct dma_buf_attachment *dma_buf_attach(struct dma_buf *dmabuf,

					  struct device *dev)

{

	struct dma_buf_attachment *attach;

	int ret;

	if (WARN_ON(!dmabuf || !dev || !dmabuf->ops))

		return ERR_PTR(-EINVAL);

	attach = kzalloc(sizeof(struct dma_buf_attachment), GFP_KERNEL);

	if (attach == NULL)

		goto err_alloc;

	mutex_lock(&dmabuf->lock);

	attach->dev = dev;

	attach->dmabuf = dmabuf;

	if (dmabuf->ops->attach) {

		ret = dmabuf->ops->attach(dmabuf, dev, attach);

		if (ret)

			goto err_attach;

	}

	list_add(&attach->node, &dmabuf->attachments);

	mutex_unlock(&dmabuf->lock);

	return attach;

err_alloc:

	return ERR_PTR(-ENOMEM);

err_attach:

	kfree(attach);

	mutex_unlock(&dmabuf->lock);

	return ERR_PTR(ret);

}

EXPORT_SYMBOL_GPL(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)

{

	if (WARN_ON(!dmabuf || !attach || !dmabuf->ops))

		return;

	mutex_lock(&dmabuf->lock);

	list_del(&attach->node);

	if (dmabuf->ops->detach)

		dmabuf->ops->detach(dmabuf, attach);

	mutex_unlock(&dmabuf->lock);

	kfree(attach);

}

EXPORT_SYMBOL_GPL(dma_buf_detach);

/**

 * dma_buf_map_attachment - Returns the scatterlist table of the attachment;

 * mapped into _device_ address space. Is a wrapper for map_dma_buf() of the

 * dma_buf_ops.

 * @attach:	[in]	attachment whose scatterlist is to be returned

 * @direction:	[in]	direction of DMA transfer

 *

 * Returns sg_table containing the scatterlist to be returned; may return NULL

 * or ERR_PTR.

 *

 */

struct sg_table *dma_buf_map_attachment(struct dma_buf_attachment *attach,

					enum dma_data_direction direction)

{

	struct sg_table *sg_table = ERR_PTR(-EINVAL);

	might_sleep();

	if (WARN_ON(!attach || !attach->dmabuf || !attach->dmabuf->ops))

		return ERR_PTR(-EINVAL);

	mutex_lock(&attach->dmabuf->lock);

	if (attach->dmabuf->ops->map_dma_buf)

		sg_table = attach->dmabuf->ops->map_dma_buf(attach, direction);

	mutex_unlock(&attach->dmabuf->lock);

	return sg_table;

}

EXPORT_SYMBOL_GPL(dma_buf_map_attachment);

/**

 * dma_buf_unmap_attachment - unmaps and decreases usecount of the buffer;might

 * deallocate the scatterlist associated. Is a wrapper for unmap_dma_buf() of

 * dma_buf_ops.

 * @attach:	[in]	attachment to unmap buffer from

 * @sg_table:	[in]	scatterlist info of the buffer to unmap

 *

 */

void dma_buf_unmap_attachment(struct dma_buf_attachment *attach,

				struct sg_table *sg_table)

{

	if (WARN_ON(!attach || !attach->dmabuf || !sg_table

			    || !attach->dmabuf->ops))

		return;

	mutex_lock(&attach->dmabuf->lock);

	if (attach->dmabuf->ops->unmap_dma_buf)

		attach->dmabuf->ops->unmap_dma_buf(attach, sg_table);

	mutex_unlock(&attach->dmabuf->lock);

}

EXPORT_SYMBOL_GPL(dma_buf_unmap_attachment);

/*

 * Header file for dma buffer sharing framework.

 *

 * 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/>.

 */

#ifndef __DMA_BUF_H__

#define __DMA_BUF_H__

#include <linux/file.h>

#include <linux/err.h>

#include <linux/device.h>

#include <linux/scatterlist.h>

#include <linux/list.h>

#include <linux/dma-mapping.h>

struct dma_buf;

struct dma_buf_attachment;

/**

 * struct dma_buf_ops - operations possible on struct dma_buf

 * @attach: [optional] allows different devices to 'attach' themselves to the

 *	    given buffer. It might return -EBUSY to signal that backing storage

 *	    is already allocated and incompatible with the requirements

 *	    of requesting device.

 * @detach: [optional] detach a given device from this buffer.

 * @map_dma_buf: returns list of scatter pages allocated, increases usecount

 *		 of the buffer. Requires atleast one attach to be called

 *		 before. Returned sg list should already be mapped into

 *		 _device_ address space. This call may sleep. May also return

 *		 -EINTR. Should return -EINVAL if attach hasn't been called yet.

 * @unmap_dma_buf: decreases usecount of buffer, might deallocate scatter

 *		   pages.

 * @release: release this buffer; to be called after the last dma_buf_put.

 */

struct dma_buf_ops {

	int (*attach)(struct dma_buf *, struct device *,

			struct dma_buf_attachment *);

	void (*detach)(struct dma_buf *, struct dma_buf_attachment *);

	/* For {map,unmap}_dma_buf below, any specific buffer attributes

	 * required should get added to device_dma_parameters accessible

	 * via dev->dma_params.

	 */

	struct sg_table * (*map_dma_buf)(struct dma_buf_attachment *,

						enum dma_data_direction);

	void (*unmap_dma_buf)(struct dma_buf_attachment *,

						struct sg_table *);

	/* TODO: Add try_map_dma_buf version, to return immed with -EBUSY

	 * if the call would block.

	 */

	/* after final dma_buf_put() */

	void (*release)(struct dma_buf *);

};

/**

 * struct dma_buf - shared buffer object

 * @size: size of the buffer

 * @file: file pointer used for sharing buffers across, and for refcounting.

 * @attachments: list of dma_buf_attachment that denotes all devices attached.

 * @ops: dma_buf_ops associated with this buffer object.

 * @priv: exporter specific private data for this buffer object.

 */

struct dma_buf {

	size_t size;

	struct file *file;

	struct list_head attachments;

	const struct dma_buf_ops *ops;

	/* mutex to serialize list manipulation and other ops */

	struct mutex lock;

	void *priv;

};

/**

 * struct dma_buf_attachment - holds device-buffer attachment data

 * @dmabuf: buffer for this attachment.

 * @dev: device attached to the buffer.

 * @node: list of dma_buf_attachment.

 * @priv: exporter specific attachment data.

 *

 * This structure holds the attachment information between the dma_buf buffer

 * and its user device(s). The list contains one attachment struct per device

 * attached to the buffer.

 */

struct dma_buf_attachment {

	struct dma_buf *dmabuf;

	struct device *dev;

	struct list_head node;

	void *priv;

};

#ifdef CONFIG_DMA_SHARED_BUFFER

struct dma_buf_attachment *dma_buf_attach(struct dma_buf *dmabuf,

							struct device *dev);

void dma_buf_detach(struct dma_buf *dmabuf,

				struct dma_buf_attachment *dmabuf_attach);

struct dma_buf *dma_buf_export(void *priv, struct dma_buf_ops *ops,

			size_t size, int flags);

int dma_buf_fd(struct dma_buf *dmabuf);

struct dma_buf *dma_buf_get(int fd);

void dma_buf_put(struct dma_buf *dmabuf);

struct sg_table *dma_buf_map_attachment(struct dma_buf_attachment *,

					enum dma_data_direction);

void dma_buf_unmap_attachment(struct dma_buf_attachment *, struct sg_table *);

#else

static inline struct dma_buf_attachment *dma_buf_attach(struct dma_buf *dmabuf,

							struct device *dev)

{

	return ERR_PTR(-ENODEV);

}

static inline void dma_buf_detach(struct dma_buf *dmabuf,

				  struct dma_buf_attachment *dmabuf_attach)

{

	return;

}

static inline struct dma_buf *dma_buf_export(void *priv,

						struct dma_buf_ops *ops,

						size_t size, int flags)

{

	return ERR_PTR(-ENODEV);

}

static inline int dma_buf_fd(struct dma_buf *dmabuf)

{

	return -ENODEV;

}

static inline struct dma_buf *dma_buf_get(int fd)

{

	return ERR_PTR(-ENODEV);

}

static inline void dma_buf_put(struct dma_buf *dmabuf)

{

	return;

}

static inline struct sg_table *dma_buf_map_attachment(

	struct dma_buf_attachment *attach, enum dma_data_direction write)

{

	return ERR_PTR(-ENODEV);

}

static inline void dma_buf_unmap_attachment(struct dma_buf_attachment *attach,

						struct sg_table *sg)

{

	return;

}

#endif /* CONFIG_DMA_SHARED_BUFFER */

#endif /* __DMA_BUF_H__ */