1/* SPDX-License-Identifier: GPL-2.0 WITH Linux-syscall-note */
  2/*
  3 * Framework for buffer objects that can be shared across devices/subsystems.
  4 *
  5 * Copyright(C) 2015 Intel Ltd
  6 *
  7 * This program is free software; you can redistribute it and/or modify it
  8 * under the terms of the GNU General Public License version 2 as published by
  9 * the Free Software Foundation.
 10 *
 11 * This program is distributed in the hope that it will be useful, but WITHOUT
 12 * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
 13 * FITNESS FOR A PARTICULAR PURPOSE.  See the GNU General Public License for
 14 * more details.
 15 *
 16 * You should have received a copy of the GNU General Public License along with
 17 * this program.  If not, see <http://www.gnu.org/licenses/>.
 18 */
 19
 20#ifndef _DMA_BUF_UAPI_H_
 21#define _DMA_BUF_UAPI_H_
 22
 23#include <linux/types.h>
 24
 25/**
 26 * struct dma_buf_sync - Synchronize with CPU access.
 27 *
 28 * When a DMA buffer is accessed from the CPU via mmap, it is not always
 29 * possible to guarantee coherency between the CPU-visible map and underlying
 30 * memory.  To manage coherency, DMA_BUF_IOCTL_SYNC must be used to bracket
 31 * any CPU access to give the kernel the chance to shuffle memory around if
 32 * needed.
 33 *
 34 * Prior to accessing the map, the client must call DMA_BUF_IOCTL_SYNC
 35 * with DMA_BUF_SYNC_START and the appropriate read/write flags.  Once the
 36 * access is complete, the client should call DMA_BUF_IOCTL_SYNC with
 37 * DMA_BUF_SYNC_END and the same read/write flags.
 38 *
 39 * The synchronization provided via DMA_BUF_IOCTL_SYNC only provides cache
 40 * coherency.  It does not prevent other processes or devices from
 41 * accessing the memory at the same time.  If synchronization with a GPU or
 42 * other device driver is required, it is the client's responsibility to
 43 * wait for buffer to be ready for reading or writing before calling this
 44 * ioctl with DMA_BUF_SYNC_START.  Likewise, the client must ensure that
 45 * follow-up work is not submitted to GPU or other device driver until
 46 * after this ioctl has been called with DMA_BUF_SYNC_END?
 47 *
 48 * If the driver or API with which the client is interacting uses implicit
 49 * synchronization, waiting for prior work to complete can be done via
 50 * poll() on the DMA buffer file descriptor.  If the driver or API requires
 51 * explicit synchronization, the client may have to wait on a sync_file or
 52 * other synchronization primitive outside the scope of the DMA buffer API.
 53 */
 54struct dma_buf_sync {
 55	/**
 56	 * @flags: Set of access flags
 57	 *
 58	 * DMA_BUF_SYNC_START:
 59	 *     Indicates the start of a map access session.
 60	 *
 61	 * DMA_BUF_SYNC_END:
 62	 *     Indicates the end of a map access session.
 63	 *
 64	 * DMA_BUF_SYNC_READ:
 65	 *     Indicates that the mapped DMA buffer will be read by the
 66	 *     client via the CPU map.
 67	 *
 68	 * DMA_BUF_SYNC_WRITE:
 69	 *     Indicates that the mapped DMA buffer will be written by the
 70	 *     client via the CPU map.
 71	 *
 72	 * DMA_BUF_SYNC_RW:
 73	 *     An alias for DMA_BUF_SYNC_READ | DMA_BUF_SYNC_WRITE.
 74	 */
 75	__u64 flags;
 76};
 77
 78#define DMA_BUF_SYNC_READ      (1 << 0)
 79#define DMA_BUF_SYNC_WRITE     (2 << 0)
 80#define DMA_BUF_SYNC_RW        (DMA_BUF_SYNC_READ | DMA_BUF_SYNC_WRITE)
 81#define DMA_BUF_SYNC_START     (0 << 2)
 82#define DMA_BUF_SYNC_END       (1 << 2)
 83#define DMA_BUF_SYNC_VALID_FLAGS_MASK \
 84	(DMA_BUF_SYNC_RW | DMA_BUF_SYNC_END)
 85
 86#define DMA_BUF_NAME_LEN	32
 87
 88/**
 89 * struct dma_buf_export_sync_file - Get a sync_file from a dma-buf
 90 *
 91 * Userspace can perform a DMA_BUF_IOCTL_EXPORT_SYNC_FILE to retrieve the
 92 * current set of fences on a dma-buf file descriptor as a sync_file.  CPU
 93 * waits via poll() or other driver-specific mechanisms typically wait on
 94 * whatever fences are on the dma-buf at the time the wait begins.  This
 95 * is similar except that it takes a snapshot of the current fences on the
 96 * dma-buf for waiting later instead of waiting immediately.  This is
 97 * useful for modern graphics APIs such as Vulkan which assume an explicit
 98 * synchronization model but still need to inter-operate with dma-buf.
 99 *
100 * The intended usage pattern is the following:
101 *
102 *  1. Export a sync_file with flags corresponding to the expected GPU usage
103 *     via DMA_BUF_IOCTL_EXPORT_SYNC_FILE.
104 *
105 *  2. Submit rendering work which uses the dma-buf.  The work should wait on
106 *     the exported sync file before rendering and produce another sync_file
107 *     when complete.
108 *
109 *  3. Import the rendering-complete sync_file into the dma-buf with flags
110 *     corresponding to the GPU usage via DMA_BUF_IOCTL_IMPORT_SYNC_FILE.
111 *
112 * Unlike doing implicit synchronization via a GPU kernel driver's exec ioctl,
113 * the above is not a single atomic operation.  If userspace wants to ensure
114 * ordering via these fences, it is the respnosibility of userspace to use
115 * locks or other mechanisms to ensure that no other context adds fences or
116 * submits work between steps 1 and 3 above.
117 */
118struct dma_buf_export_sync_file {
119	/**
120	 * @flags: Read/write flags
121	 *
122	 * Must be DMA_BUF_SYNC_READ, DMA_BUF_SYNC_WRITE, or both.
123	 *
124	 * If DMA_BUF_SYNC_READ is set and DMA_BUF_SYNC_WRITE is not set,
125	 * the returned sync file waits on any writers of the dma-buf to
126	 * complete.  Waiting on the returned sync file is equivalent to
127	 * poll() with POLLIN.
128	 *
129	 * If DMA_BUF_SYNC_WRITE is set, the returned sync file waits on
130	 * any users of the dma-buf (read or write) to complete.  Waiting
131	 * on the returned sync file is equivalent to poll() with POLLOUT.
132	 * If both DMA_BUF_SYNC_WRITE and DMA_BUF_SYNC_READ are set, this
133	 * is equivalent to just DMA_BUF_SYNC_WRITE.
134	 */
135	__u32 flags;
136	/** @fd: Returned sync file descriptor */
137	__s32 fd;
138};
139
140/**
141 * struct dma_buf_import_sync_file - Insert a sync_file into a dma-buf
142 *
143 * Userspace can perform a DMA_BUF_IOCTL_IMPORT_SYNC_FILE to insert a
144 * sync_file into a dma-buf for the purposes of implicit synchronization
145 * with other dma-buf consumers.  This allows clients using explicitly
146 * synchronized APIs such as Vulkan to inter-op with dma-buf consumers
147 * which expect implicit synchronization such as OpenGL or most media
148 * drivers/video.
149 */
150struct dma_buf_import_sync_file {
151	/**
152	 * @flags: Read/write flags
153	 *
154	 * Must be DMA_BUF_SYNC_READ, DMA_BUF_SYNC_WRITE, or both.
155	 *
156	 * If DMA_BUF_SYNC_READ is set and DMA_BUF_SYNC_WRITE is not set,
157	 * this inserts the sync_file as a read-only fence.  Any subsequent
158	 * implicitly synchronized writes to this dma-buf will wait on this
159	 * fence but reads will not.
160	 *
161	 * If DMA_BUF_SYNC_WRITE is set, this inserts the sync_file as a
162	 * write fence.  All subsequent implicitly synchronized access to
163	 * this dma-buf will wait on this fence.
164	 */
165	__u32 flags;
166	/** @fd: Sync file descriptor */
167	__s32 fd;
168};
169
170#define DMA_BUF_BASE		'b'
171#define DMA_BUF_IOCTL_SYNC	_IOW(DMA_BUF_BASE, 0, struct dma_buf_sync)
172
173/* 32/64bitness of this uapi was botched in android, there's no difference
174 * between them in actual uapi, they're just different numbers.
175 */
176#define DMA_BUF_SET_NAME	_IOW(DMA_BUF_BASE, 1, const char *)
177#define DMA_BUF_SET_NAME_A	_IOW(DMA_BUF_BASE, 1, __u32)
178#define DMA_BUF_SET_NAME_B	_IOW(DMA_BUF_BASE, 1, __u64)
179#define DMA_BUF_IOCTL_EXPORT_SYNC_FILE	_IOWR(DMA_BUF_BASE, 2, struct dma_buf_export_sync_file)
180#define DMA_BUF_IOCTL_IMPORT_SYNC_FILE	_IOW(DMA_BUF_BASE, 3, struct dma_buf_import_sync_file)
181
182#endif