dma-buf.h (7321B) - Raw
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 */ 54 struct 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 */ 118 struct 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 */ 150 struct 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