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 /* 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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