/* SPDX-License-Identifier: GPL-2.0 WITH Linux-syscall-note */ /* * Framework for buffer objects that can be shared across devices/subsystems. * * Copyright(C) 2015 Intel Ltd * * 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_UAPI_H_ #define _DMA_BUF_UAPI_H_ #include <linux/types.h> /** * struct dma_buf_sync - Synchronize with CPU access. * * When a DMA buffer is accessed from the CPU via mmap, it is not always * possible to guarantee coherency between the CPU-visible map and underlying * memory. To manage coherency, DMA_BUF_IOCTL_SYNC must be used to bracket * any CPU access to give the kernel the chance to shuffle memory around if * needed. * * Prior to accessing the map, the client must call DMA_BUF_IOCTL_SYNC * with DMA_BUF_SYNC_START and the appropriate read/write flags. Once the * access is complete, the client should call DMA_BUF_IOCTL_SYNC with * DMA_BUF_SYNC_END and the same read/write flags. * * The synchronization provided via DMA_BUF_IOCTL_SYNC only provides cache * coherency. It does not prevent other processes or devices from * accessing the memory at the same time. If synchronization with a GPU or * other device driver is required, it is the client's responsibility to * wait for buffer to be ready for reading or writing before calling this * ioctl with DMA_BUF_SYNC_START. Likewise, the client must ensure that * follow-up work is not submitted to GPU or other device driver until * after this ioctl has been called with DMA_BUF_SYNC_END? * * If the driver or API with which the client is interacting uses implicit * synchronization, waiting for prior work to complete can be done via * poll() on the DMA buffer file descriptor. If the driver or API requires * explicit synchronization, the client may have to wait on a sync_file or * other synchronization primitive outside the scope of the DMA buffer API. */ struct dma_buf_sync { … }; #define DMA_BUF_SYNC_READ … #define DMA_BUF_SYNC_WRITE … #define DMA_BUF_SYNC_RW … #define DMA_BUF_SYNC_START … #define DMA_BUF_SYNC_END … #define DMA_BUF_SYNC_VALID_FLAGS_MASK … #define DMA_BUF_NAME_LEN … /** * struct dma_buf_export_sync_file - Get a sync_file from a dma-buf * * Userspace can perform a DMA_BUF_IOCTL_EXPORT_SYNC_FILE to retrieve the * current set of fences on a dma-buf file descriptor as a sync_file. CPU * waits via poll() or other driver-specific mechanisms typically wait on * whatever fences are on the dma-buf at the time the wait begins. This * is similar except that it takes a snapshot of the current fences on the * dma-buf for waiting later instead of waiting immediately. This is * useful for modern graphics APIs such as Vulkan which assume an explicit * synchronization model but still need to inter-operate with dma-buf. * * The intended usage pattern is the following: * * 1. Export a sync_file with flags corresponding to the expected GPU usage * via DMA_BUF_IOCTL_EXPORT_SYNC_FILE. * * 2. Submit rendering work which uses the dma-buf. The work should wait on * the exported sync file before rendering and produce another sync_file * when complete. * * 3. Import the rendering-complete sync_file into the dma-buf with flags * corresponding to the GPU usage via DMA_BUF_IOCTL_IMPORT_SYNC_FILE. * * Unlike doing implicit synchronization via a GPU kernel driver's exec ioctl, * the above is not a single atomic operation. If userspace wants to ensure * ordering via these fences, it is the respnosibility of userspace to use * locks or other mechanisms to ensure that no other context adds fences or * submits work between steps 1 and 3 above. */ struct dma_buf_export_sync_file { … }; /** * struct dma_buf_import_sync_file - Insert a sync_file into a dma-buf * * Userspace can perform a DMA_BUF_IOCTL_IMPORT_SYNC_FILE to insert a * sync_file into a dma-buf for the purposes of implicit synchronization * with other dma-buf consumers. This allows clients using explicitly * synchronized APIs such as Vulkan to inter-op with dma-buf consumers * which expect implicit synchronization such as OpenGL or most media * drivers/video. */ struct dma_buf_import_sync_file { … }; #define DMA_BUF_BASE … #define DMA_BUF_IOCTL_SYNC … /* 32/64bitness of this uapi was botched in android, there's no difference * between them in actual uapi, they're just different numbers. */ #define DMA_BUF_SET_NAME … #define DMA_BUF_SET_NAME_A … #define DMA_BUF_SET_NAME_B … #define DMA_BUF_IOCTL_EXPORT_SYNC_FILE … #define DMA_BUF_IOCTL_IMPORT_SYNC_FILE … #endif
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