From aa4533639971d772ce35cf5f39bee4c4a3628b7d Mon Sep 17 00:00:00 2001 From: David Plowman Date: Wed, 5 Jan 2022 15:55:37 +0000 Subject: include: linux: Update kernel headers to version v5.16-rc7 Updated kernel headers to v5.16-rc7 using utils/update-kernel-headers.sh and re-instating libcamera local modifications. Signed-off-by: David Plowman Reviewed-by: Laurent Pinchart Signed-off-by: Laurent Pinchart --- include/linux/dma-buf.h | 50 ++++++++++++++++++++++++++++++++++++++++++++++++- 1 file changed, 49 insertions(+), 1 deletion(-) (limited to 'include/linux/dma-buf.h') diff --git a/include/linux/dma-buf.h b/include/linux/dma-buf.h index 7f30393b..8e4a2ca0 100644 --- a/include/linux/dma-buf.h +++ b/include/linux/dma-buf.h @@ -22,8 +22,56 @@ #include -/* begin/end dma-buf functions used for userspace mmap. */ +/** + * 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; }; -- cgit v1.2.1