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Diffstat (limited to 'include/uapi/linux/dma-buf.h')
| -rw-r--r-- | include/uapi/linux/dma-buf.h | 182 |
1 files changed, 182 insertions, 0 deletions
diff --git a/include/uapi/linux/dma-buf.h b/include/uapi/linux/dma-buf.h new file mode 100644 index 0000000000..5a6fda66d9 --- /dev/null +++ b/include/uapi/linux/dma-buf.h @@ -0,0 +1,182 @@ +/* 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 { + /** + * @flags: Set of access flags + * + * DMA_BUF_SYNC_START: + * Indicates the start of a map access session. + * + * DMA_BUF_SYNC_END: + * Indicates the end of a map access session. + * + * DMA_BUF_SYNC_READ: + * Indicates that the mapped DMA buffer will be read by the + * client via the CPU map. + * + * DMA_BUF_SYNC_WRITE: + * Indicates that the mapped DMA buffer will be written by the + * client via the CPU map. + * + * DMA_BUF_SYNC_RW: + * An alias for DMA_BUF_SYNC_READ | DMA_BUF_SYNC_WRITE. + */ + __u64 flags; +}; + +#define DMA_BUF_SYNC_READ (1 << 0) +#define DMA_BUF_SYNC_WRITE (2 << 0) +#define DMA_BUF_SYNC_RW (DMA_BUF_SYNC_READ | DMA_BUF_SYNC_WRITE) +#define DMA_BUF_SYNC_START (0 << 2) +#define DMA_BUF_SYNC_END (1 << 2) +#define DMA_BUF_SYNC_VALID_FLAGS_MASK \ + (DMA_BUF_SYNC_RW | DMA_BUF_SYNC_END) + +#define DMA_BUF_NAME_LEN 32 + +/** + * 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 { + /** + * @flags: Read/write flags + * + * Must be DMA_BUF_SYNC_READ, DMA_BUF_SYNC_WRITE, or both. + * + * If DMA_BUF_SYNC_READ is set and DMA_BUF_SYNC_WRITE is not set, + * the returned sync file waits on any writers of the dma-buf to + * complete. Waiting on the returned sync file is equivalent to + * poll() with POLLIN. + * + * If DMA_BUF_SYNC_WRITE is set, the returned sync file waits on + * any users of the dma-buf (read or write) to complete. Waiting + * on the returned sync file is equivalent to poll() with POLLOUT. + * If both DMA_BUF_SYNC_WRITE and DMA_BUF_SYNC_READ are set, this + * is equivalent to just DMA_BUF_SYNC_WRITE. + */ + __u32 flags; + /** @fd: Returned sync file descriptor */ + __s32 fd; +}; + +/** + * 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 { + /** + * @flags: Read/write flags + * + * Must be DMA_BUF_SYNC_READ, DMA_BUF_SYNC_WRITE, or both. + * + * If DMA_BUF_SYNC_READ is set and DMA_BUF_SYNC_WRITE is not set, + * this inserts the sync_file as a read-only fence. Any subsequent + * implicitly synchronized writes to this dma-buf will wait on this + * fence but reads will not. + * + * If DMA_BUF_SYNC_WRITE is set, this inserts the sync_file as a + * write fence. All subsequent implicitly synchronized access to + * this dma-buf will wait on this fence. + */ + __u32 flags; + /** @fd: Sync file descriptor */ + __s32 fd; +}; + +#define DMA_BUF_BASE 'b' +#define DMA_BUF_IOCTL_SYNC _IOW(DMA_BUF_BASE, 0, struct dma_buf_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 _IOW(DMA_BUF_BASE, 1, const char *) +#define DMA_BUF_SET_NAME_A _IOW(DMA_BUF_BASE, 1, __u32) +#define DMA_BUF_SET_NAME_B _IOW(DMA_BUF_BASE, 1, __u64) +#define DMA_BUF_IOCTL_EXPORT_SYNC_FILE _IOWR(DMA_BUF_BASE, 2, struct dma_buf_export_sync_file) +#define DMA_BUF_IOCTL_IMPORT_SYNC_FILE _IOW(DMA_BUF_BASE, 3, struct dma_buf_import_sync_file) + +#endif |