dma-buf.h
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/*
* 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__ */