/* 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
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