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
dma_buf_attach(struct dma_buf * dmabuf,struct device * dev)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
dma_buf_detach(struct dma_buf * dmabuf,struct dma_buf_attachment * dmabuf_attach)134 static inline void dma_buf_detach(struct dma_buf *dmabuf,
135 struct dma_buf_attachment *dmabuf_attach)
136 {
137 return;
138 }
139
dma_buf_export(void * priv,struct dma_buf_ops * ops,size_t size,int flags)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
dma_buf_fd(struct dma_buf * dmabuf)147 static inline int dma_buf_fd(struct dma_buf *dmabuf)
148 {
149 return -ENODEV;
150 }
151
dma_buf_get(int fd)152 static inline struct dma_buf *dma_buf_get(int fd)
153 {
154 return ERR_PTR(-ENODEV);
155 }
156
dma_buf_put(struct dma_buf * dmabuf)157 static inline void dma_buf_put(struct dma_buf *dmabuf)
158 {
159 return;
160 }
161
dma_buf_map_attachment(struct dma_buf_attachment * attach,enum dma_data_direction write)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
dma_buf_unmap_attachment(struct dma_buf_attachment * attach,struct sg_table * sg)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__ */
177