include/linux/dma-buf.h

   1 /*
   2  * Header file for dma buffer sharing framework.
   3  *
   4  * Copyright(C) 2011 Linaro Limited. All rights reserved.
   5  * Author: Sumit Semwal <sumit.semwal@ti.com>
   6  *
   7  * Many thanks to linaro-mm-sig list, and specially
   8  * Arnd Bergmann <arnd@arndb.de>, Rob Clark <rob@ti.com> and
   9  * Daniel Vetter <daniel@ffwll.ch> for their support in creation and
  10  * refining of this idea.
  11  *
  12  * This program is free software; you can redistribute it and/or modify it
  13  * under the terms of the GNU General Public License version 2 as published by
  14  * the Free Software Foundation.
  15  *
  16  * This program is distributed in the hope that it will be useful, but WITHOUT
  17  * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
  18  * FITNESS FOR A PARTICULAR PURPOSE.  See the GNU General Public License for
  19  * more details.
  20  *
  21  * You should have received a copy of the GNU General Public License along with
  22  * this program.  If not, see <http://www.gnu.org/licenses/>.
  23  */
  24 #ifndef __DMA_BUF_H__
  25 #define __DMA_BUF_H__
  26
  27 #include <linux/file.h>
  28 #include <linux/err.h>
  29 #include <linux/device.h>
  30 #include <linux/scatterlist.h>
  31 #include <linux/list.h>
  32 #include <linux/dma-mapping.h>
  33
  34 struct dma_buf;
  35 struct dma_buf_attachment;
  36
  37 /**
  38  * struct dma_buf_ops - operations possible on struct dma_buf
  39  * @attach: [optional] allows different devices to 'attach' themselves to the
  40  *          given buffer. It might return -EBUSY to signal that backing storage
  41  *          is already allocated and incompatible with the requirements
  42  *          of requesting device.
  43  * @detach: [optional] detach a given device from this buffer.
  44  * @map_dma_buf: returns list of scatter pages allocated, increases usecount
  45  *               of the buffer. Requires atleast one attach to be called
  46  *               before. Returned sg list should already be mapped into
  47  *               _device_ address space. This call may sleep. May also return
  48  *               -EINTR. Should return -EINVAL if attach hasn't been called yet.
  49  * @unmap_dma_buf: decreases usecount of buffer, might deallocate scatter
  50  *                 pages.
  51  * @release: release this buffer; to be called after the last dma_buf_put.
  52  */
  53 struct dma_buf_ops {
  54         int (*attach)(struct dma_buf *, struct device *,
  55                         struct dma_buf_attachment *);
  56
  57         void (*detach)(struct dma_buf *, struct dma_buf_attachment *);
  58
  59         /* For {map,unmap}_dma_buf below, any specific buffer attributes
  60          * required should get added to device_dma_parameters accessible
  61          * via dev->dma_params.
  62          */
  63         struct sg_table * (*map_dma_buf)(struct dma_buf_attachment *,
  64                                                 enum dma_data_direction);
  65         void (*unmap_dma_buf)(struct dma_buf_attachment *,
  66                                                 struct sg_table *);
  67         /* TODO: Add try_map_dma_buf version, to return immed with -EBUSY
  68          * if the call would block.
  69          */
  70
  71         /* after final dma_buf_put() */
  72         void (*release)(struct dma_buf *);
  73
  74 };
  75
  76 /**
  77  * struct dma_buf - shared buffer object
  78  * @size: size of the buffer
  79  * @file: file pointer used for sharing buffers across, and for refcounting.
  80  * @attachments: list of dma_buf_attachment that denotes all devices attached.
  81  * @ops: dma_buf_ops associated with this buffer object.
  82  * @priv: exporter specific private data for this buffer object.
  83  */
  84 struct dma_buf {
  85         size_t size;
  86         struct file *file;
  87         struct list_head attachments;
  88         const struct dma_buf_ops *ops;
  89         /* mutex to serialize list manipulation and other ops */
  90         struct mutex lock;
  91         void *priv;
  92 };
  93
  94 /**
  95  * struct dma_buf_attachment - holds device-buffer attachment data
  96  * @dmabuf: buffer for this attachment.
  97  * @dev: device attached to the buffer.
  98  * @node: list of dma_buf_attachment.
  99  * @priv: exporter specific attachment data.
 100  *
 101  * This structure holds the attachment information between the dma_buf buffer
 102  * and its user device(s). The list contains one attachment struct per device
 103  * attached to the buffer.
 104  */
 105 struct dma_buf_attachment {
 106         struct dma_buf *dmabuf;
 107         struct device *dev;
 108         struct list_head node;
 109         void *priv;
 110 };
 111
 112 #ifdef CONFIG_DMA_SHARED_BUFFER
 113 struct dma_buf_attachment *dma_buf_attach(struct dma_buf *dmabuf,
 114                                                         struct device *dev);
 115 void dma_buf_detach(struct dma_buf *dmabuf,
 116                                 struct dma_buf_attachment *dmabuf_attach);
 117 struct dma_buf *dma_buf_export(void *priv, struct dma_buf_ops *ops,
 118                         size_t size, int flags);
 119 int dma_buf_fd(struct dma_buf *dmabuf);
 120 struct dma_buf *dma_buf_get(int fd);
 121 void dma_buf_put(struct dma_buf *dmabuf);
 122
 123 struct sg_table *dma_buf_map_attachment(struct dma_buf_attachment *,
 124                                         enum dma_data_direction);
 125 void dma_buf_unmap_attachment(struct dma_buf_attachment *, struct sg_table *);
 126 #else
 127
 128 static inline struct dma_buf_attachment *dma_buf_attach(struct dma_buf *dmabuf,
 129                                                         struct device *dev)
 130 {
 131         return ERR_PTR(-ENODEV);
 132 }
 133
 134 static inline void dma_buf_detach(struct dma_buf *dmabuf,
 135                                   struct dma_buf_attachment *dmabuf_attach)
 136 {
 137         return;
 138 }
 139
 140 static inline struct dma_buf *dma_buf_export(void *priv,
 141                                                 struct dma_buf_ops *ops,
 142                                                 size_t size, int flags)
 143 {
 144         return ERR_PTR(-ENODEV);
 145 }
 146
 147 static inline int dma_buf_fd(struct dma_buf *dmabuf)
 148 {
 149         return -ENODEV;
 150 }
 151
 152 static inline struct dma_buf *dma_buf_get(int fd)
 153 {
 154         return ERR_PTR(-ENODEV);
 155 }
 156
 157 static inline void dma_buf_put(struct dma_buf *dmabuf)
 158 {
 159         return;
 160 }
 161
 162 static inline struct sg_table *dma_buf_map_attachment(
 163         struct dma_buf_attachment *attach, enum dma_data_direction write)
 164 {
 165         return ERR_PTR(-ENODEV);
 166 }
 167
 168 static inline void dma_buf_unmap_attachment(struct dma_buf_attachment *attach,
 169                                                 struct sg_table *sg)
 170 {
 171         return;
 172 }
 173
 174 #endif /* CONFIG_DMA_SHARED_BUFFER */
 175
 176 #endif /* __DMA_BUF_H__ */