diff options
Diffstat (limited to 'include')
| -rw-r--r-- | include/linux/dma-buf.h | 25 |
1 files changed, 9 insertions, 16 deletions
diff --git a/include/linux/dma-buf.h b/include/linux/dma-buf.h index cf72699cb2bc..7eca37c8b10c 100644 --- a/include/linux/dma-buf.h +++ b/include/linux/dma-buf.h @@ -183,24 +183,19 @@ struct dma_buf_ops { * @begin_cpu_access: * * This is called from dma_buf_begin_cpu_access() and allows the - * exporter to ensure that the memory is actually available for cpu - * access - the exporter might need to allocate or swap-in and pin the - * backing storage. The exporter also needs to ensure that cpu access is - * coherent for the access direction. The direction can be used by the - * exporter to optimize the cache flushing, i.e. access with a different + * exporter to ensure that the memory is actually coherent for cpu + * access. The exporter also needs to ensure that cpu access is coherent + * for the access direction. The direction can be used by the exporter + * to optimize the cache flushing, i.e. access with a different * direction (read instead of write) might return stale or even bogus * data (e.g. when the exporter needs to copy the data to temporary * storage). * - * This callback is optional. + * Note that this is both called through the DMA_BUF_IOCTL_SYNC IOCTL + * command for userspace mappings established through @mmap, and also + * for kernel mappings established with @vmap. * - * FIXME: This is both called through the DMA_BUF_IOCTL_SYNC command - * from userspace (where storage shouldn't be pinned to avoid handing - * de-factor mlock rights to userspace) and for the kernel-internal - * users of the various kmap interfaces, where the backing storage must - * be pinned to guarantee that the atomic kmap calls can succeed. Since - * there's no in-kernel users of the kmap interfaces yet this isn't a - * real problem. + * This callback is optional. * * Returns: * @@ -216,9 +211,7 @@ struct dma_buf_ops { * * This is called from dma_buf_end_cpu_access() when the importer is * done accessing the CPU. The exporter can use this to flush caches and - * unpin any resources pinned in @begin_cpu_access. - * The result of any dma_buf kmap calls after end_cpu_access is - * undefined. + * undo anything else done in @begin_cpu_access. * * This callback is optional. * |