summaryrefslogtreecommitdiff
path: root/include/linux/dma-buf.h
blob: 58725f890b5b6185cda07d48591d9f1162f78c3d (plain)
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
93
94
95
96
97
98
99
100
101
102
103
104
105
106
107
108
109
110
111
112
113
114
115
116
117
118
119
120
121
122
123
124
125
126
127
128
129
130
131
132
133
134
135
136
137
138
139
140
141
142
143
144
145
146
147
148
149
150
151
152
153
154
155
156
157
158
159
160
161
162
163
164
165
166
167
168
169
170
171
172
173
174
175
176
177
178
179
180
181
182
183
184
185
186
187
188
189
190
191
192
193
194
195
196
197
198
199
200
201
202
203
204
205
206
207
208
209
210
211
212
213
214
215
216
217
218
219
220
221
222
223
224
225
226
227
228
229
230
231
232
233
234
235
236
237
238
239
240
241
242
243
244
245
246
247
248
249
250
251
252
253
254
255
256
257
258
259
260
261
262
263
264
265
266
267
268
269
270
271
272
273
274
275
276
277
278
279
280
281
282
283
284
285
286
287
288
289
290
291
292
293
294
295
296
297
298
299
300
301
302
303
304
305
306
307
308
309
310
311
312
313
314
315
316
317
318
319
320
321
322
323
324
325
326
327
328
329
330
331
332
333
334
335
336
337
338
339
340
341
342
343
344
345
346
347
348
349
350
351
352
353
354
355
356
357
358
359
360
361
362
363
364
365
366
367
368
369
370
371
372
373
374
375
376
377
378
379
380
381
382
383
384
385
386
387
388
389
390
391
392
393
394
395
396
397
398
399
400
401
402
/*
 * 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/scatterlist.h>
#include <linux/list.h>
#include <linux/dma-mapping.h>
#include <linux/fs.h>
#include <linux/dma-fence.h>
#include <linux/wait.h>

struct device;
struct dma_buf;
struct dma_buf_attachment;

/**
 * struct dma_buf_ops - operations possible on struct dma_buf
 * @map_atomic: [optional] maps a page from the buffer into kernel address
 *		space, users may not block until the subsequent unmap call.
 *		This callback must not sleep.
 * @unmap_atomic: [optional] unmaps a atomically mapped page from the buffer.
 *		  This Callback must not sleep.
 * @map: [optional] maps a page from the buffer into kernel address space.
 * @unmap: [optional] unmaps a page from the buffer.
 * @vmap: [optional] creates a virtual mapping for the buffer into kernel
 *	  address space. Same restrictions as for vmap and friends apply.
 * @vunmap: [optional] unmaps a vmap from the buffer
 */
struct dma_buf_ops {
	/**
	 * @attach:
	 *
	 * This is called from dma_buf_attach() to make sure that a given
	 * &dma_buf_attachment.dev can access the provided &dma_buf. Exporters
	 * which support buffer objects in special locations like VRAM or
	 * device-specific carveout areas should check whether the buffer could
	 * be move to system memory (or directly accessed by the provided
	 * device), and otherwise need to fail the attach operation.
	 *
	 * The exporter should also in general check whether the current
	 * allocation fullfills the DMA constraints of the new device. If this
	 * is not the case, and the allocation cannot be moved, it should also
	 * fail the attach operation.
	 *
	 * Any exporter-private housekeeping data can be stored in the
	 * &dma_buf_attachment.priv pointer.
	 *
	 * This callback is optional.
	 *
	 * Returns:
	 *
	 * 0 on success, negative error code on failure. It might return -EBUSY
	 * to signal that backing storage is already allocated and incompatible
	 * with the requirements of requesting device.
	 */
	int (*attach)(struct dma_buf *, struct dma_buf_attachment *);

	/**
	 * @detach:
	 *
	 * This is called by dma_buf_detach() to release a &dma_buf_attachment.
	 * Provided so that exporters can clean up any housekeeping for an
	 * &dma_buf_attachment.
	 *
	 * This callback is optional.
	 */
	void (*detach)(struct dma_buf *, struct dma_buf_attachment *);

	/**
	 * @map_dma_buf:
	 *
	 * This is called by dma_buf_map_attachment() and is used to map a
	 * shared &dma_buf into device address space, and it is mandatory. It
	 * can only be called if @attach has been called successfully. This
	 * essentially pins the DMA buffer into place, and it cannot be moved
	 * any more
	 *
	 * This call may sleep, e.g. when the backing storage first needs to be
	 * allocated, or moved to a location suitable for all currently attached
	 * devices.
	 *
	 * Note that any specific buffer attributes required for this function
	 * should get added to device_dma_parameters accessible via
	 * &device.dma_params from the &dma_buf_attachment. The @attach callback
	 * should also check these constraints.
	 *
	 * If this is being called for the first time, the exporter can now
	 * choose to scan through the list of attachments for this buffer,
	 * collate the requirements of the attached devices, and choose an
	 * appropriate backing storage for the buffer.
	 *
	 * Based on enum dma_data_direction, it might be possible to have
	 * multiple users accessing at the same time (for reading, maybe), or
	 * any other kind of sharing that the exporter might wish to make
	 * available to buffer-users.
	 *
	 * Returns:
	 *
	 * A &sg_table scatter list of or the backing storage of the DMA buffer,
	 * already mapped into the device address space of the &device attached
	 * with the provided &dma_buf_attachment.
	 *
	 * On failure, returns a negative error value wrapped into a pointer.
	 * May also return -EINTR when a signal was received while being
	 * blocked.
	 */
	struct sg_table * (*map_dma_buf)(struct dma_buf_attachment *,
					 enum dma_data_direction);
	/**
	 * @unmap_dma_buf:
	 *
	 * This is called by dma_buf_unmap_attachment() and should unmap and
	 * release the &sg_table allocated in @map_dma_buf, and it is mandatory.
	 * It should also unpin the backing storage if this is the last mapping
	 * of the DMA buffer, it the exporter supports backing storage
	 * migration.
	 */
	void (*unmap_dma_buf)(struct dma_buf_attachment *,
			      struct sg_table *,
			      enum dma_data_direction);

	/* TODO: Add try_map_dma_buf version, to return immed with -EBUSY
	 * if the call would block.
	 */

	/**
	 * @release:
	 *
	 * Called after the last dma_buf_put to release the &dma_buf, and
	 * mandatory.
	 */
	void (*release)(struct dma_buf *);

	/**
	 * @begin_cpu_access:
	 *
	 * This is called from dma_buf_begin_cpu_access() and allows the
	 * exporter to ensure that the memory is actually available for cpu
	 * access - the exporter might need to allocate or swap-in and pin the
	 * backing storage. The exporter also needs to ensure that cpu access is
	 * coherent for the access direction. The direction can be used by the
	 * exporter to optimize the cache flushing, i.e. access with a different
	 * direction (read instead of write) might return stale or even bogus
	 * data (e.g. when the exporter needs to copy the data to temporary
	 * storage).
	 *
	 * This callback is optional.
	 *
	 * FIXME: This is both called through the DMA_BUF_IOCTL_SYNC command
	 * from userspace (where storage shouldn't be pinned to avoid handing
	 * de-factor mlock rights to userspace) and for the kernel-internal
	 * users of the various kmap interfaces, where the backing storage must
	 * be pinned to guarantee that the atomic kmap calls can succeed. Since
	 * there's no in-kernel users of the kmap interfaces yet this isn't a
	 * real problem.
	 *
	 * Returns:
	 *
	 * 0 on success or a negative error code on failure. This can for
	 * example fail when the backing storage can't be allocated. Can also
	 * return -ERESTARTSYS or -EINTR when the call has been interrupted and
	 * needs to be restarted.
	 */
	int (*begin_cpu_access)(struct dma_buf *, enum dma_data_direction);

	/**
	 * @end_cpu_access:
	 *
	 * This is called from dma_buf_end_cpu_access() when the importer is
	 * done accessing the CPU. The exporter can use this to flush caches and
	 * unpin any resources pinned in @begin_cpu_access.
	 * The result of any dma_buf kmap calls after end_cpu_access is
	 * undefined.
	 *
	 * This callback is optional.
	 *
	 * Returns:
	 *
	 * 0 on success or a negative error code on failure. Can return
	 * -ERESTARTSYS or -EINTR when the call has been interrupted and needs
	 * to be restarted.
	 */
	int (*end_cpu_access)(struct dma_buf *, enum dma_data_direction);
	void *(*map)(struct dma_buf *, unsigned long);
	void (*unmap)(struct dma_buf *, unsigned long, void *);

	/**
	 * @mmap:
	 *
	 * This callback is used by the dma_buf_mmap() function
	 *
	 * Note that the mapping needs to be incoherent, userspace is expected
	 * to braket CPU access using the DMA_BUF_IOCTL_SYNC interface.
	 *
	 * Because dma-buf buffers have invariant size over their lifetime, the
	 * dma-buf core checks whether a vma is too large and rejects such
	 * mappings. The exporter hence does not need to duplicate this check.
	 * Drivers do not need to check this themselves.
	 *
	 * If an exporter needs to manually flush caches and hence needs to fake
	 * coherency for mmap support, it needs to be able to zap all the ptes
	 * pointing at the backing storage. Now linux mm needs a struct
	 * address_space associated with the struct file stored in vma->vm_file
	 * to do that with the function unmap_mapping_range. But the dma_buf
	 * framework only backs every dma_buf fd with the anon_file struct file,
	 * i.e. all dma_bufs share the same file.
	 *
	 * Hence exporters need to setup their own file (and address_space)
	 * association by setting vma->vm_file and adjusting vma->vm_pgoff in
	 * the dma_buf mmap callback. In the specific case of a gem driver the
	 * exporter could use the shmem file already provided by gem (and set
	 * vm_pgoff = 0). Exporters can then zap ptes by unmapping the
	 * corresponding range of the struct address_space associated with their
	 * own file.
	 *
	 * This callback is optional.
	 *
	 * Returns:
	 *
	 * 0 on success or a negative error code on failure.
	 */
	int (*mmap)(struct dma_buf *, struct vm_area_struct *vma);

	void *(*vmap)(struct dma_buf *);
	void (*vunmap)(struct dma_buf *, void *vaddr);
};

/**
 * 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.
 * @lock: used internally to serialize list manipulation, attach/detach and vmap/unmap
 * @vmapping_counter: used internally to refcnt the vmaps
 * @vmap_ptr: the current vmap ptr if vmapping_counter > 0
 * @exp_name: name of the exporter; useful for debugging.
 * @owner: pointer to exporter module; used for refcounting when exporter is a
 *         kernel module.
 * @list_node: node for dma_buf accounting and debugging.
 * @priv: exporter specific private data for this buffer object.
 * @resv: reservation object linked to this dma-buf
 * @poll: for userspace poll support
 * @cb_excl: for userspace poll support
 * @cb_shared: for userspace poll support
 *
 * This represents a shared buffer, created by calling dma_buf_export(). The
 * userspace representation is a normal file descriptor, which can be created by
 * calling dma_buf_fd().
 *
 * Shared dma buffers are reference counted using dma_buf_put() and
 * get_dma_buf().
 *
 * Device DMA access is handled by the separate &struct dma_buf_attachment.
 */
struct dma_buf {
	size_t size;
	struct file *file;
	struct list_head attachments;
	const struct dma_buf_ops *ops;
	struct mutex lock;
	unsigned vmapping_counter;
	void *vmap_ptr;
	const char *exp_name;
	struct module *owner;
	struct list_head list_node;
	void *priv;
	struct reservation_object *resv;

	/* poll support */
	wait_queue_head_t poll;

	struct dma_buf_poll_cb_t {
		struct dma_fence_cb cb;
		wait_queue_head_t *poll;

		__poll_t active;
	} cb_excl, cb_shared;
};

/**
 * 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.
 *
 * An attachment is created by calling dma_buf_attach(), and released again by
 * calling dma_buf_detach(). The DMA mapping itself needed to initiate a
 * transfer is created by dma_buf_map_attachment() and freed again by calling
 * dma_buf_unmap_attachment().
 */
struct dma_buf_attachment {
	struct dma_buf *dmabuf;
	struct device *dev;
	struct list_head node;
	void *priv;
};

/**
 * struct dma_buf_export_info - holds information needed to export a dma_buf
 * @exp_name:	name of the exporter - useful for debugging.
 * @owner:	pointer to exporter module - used for refcounting kernel module
 * @ops:	Attach allocator-defined dma buf ops to the new buffer
 * @size:	Size of the buffer
 * @flags:	mode flags for the file
 * @resv:	reservation-object, NULL to allocate default one
 * @priv:	Attach private data of allocator to this buffer
 *
 * This structure holds the information required to export the buffer. Used
 * with dma_buf_export() only.
 */
struct dma_buf_export_info {
	const char *exp_name;
	struct module *owner;
	const struct dma_buf_ops *ops;
	size_t size;
	int flags;
	struct reservation_object *resv;
	void *priv;
};

/**
 * DEFINE_DMA_BUF_EXPORT_INFO - helper macro for exporters
 * @name: export-info name
 *
 * DEFINE_DMA_BUF_EXPORT_INFO macro defines the &struct dma_buf_export_info,
 * zeroes it out and pre-populates exp_name in it.
 */
#define DEFINE_DMA_BUF_EXPORT_INFO(name)	\
	struct dma_buf_export_info name = { .exp_name = KBUILD_MODNAME, \
					 .owner = THIS_MODULE }

/**
 * get_dma_buf - convenience wrapper for get_file.
 * @dmabuf:	[in]	pointer to dma_buf
 *
 * Increments the reference count on the dma-buf, needed in case of drivers
 * that either need to create additional references to the dmabuf on the
 * kernel side.  For example, an exporter that needs to keep a dmabuf ptr
 * so that subsequent exports don't create a new dmabuf.
 */
static inline void get_dma_buf(struct dma_buf *dmabuf)
{
	get_file(dmabuf->file);
}

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(const struct dma_buf_export_info *exp_info);

int dma_buf_fd(struct dma_buf *dmabuf, int flags);
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 *,
				enum dma_data_direction);
int dma_buf_begin_cpu_access(struct dma_buf *dma_buf,
			     enum dma_data_direction dir);
int dma_buf_end_cpu_access(struct dma_buf *dma_buf,
			   enum dma_data_direction dir);
void *dma_buf_kmap(struct dma_buf *, unsigned long);
void dma_buf_kunmap(struct dma_buf *, unsigned long, void *);

int dma_buf_mmap(struct dma_buf *, struct vm_area_struct *,
		 unsigned long);
void *dma_buf_vmap(struct dma_buf *);
void dma_buf_vunmap(struct dma_buf *, void *vaddr);
#endif /* __DMA_BUF_H__ */