[Linaro-mm-sig] Re: [PATCH 1/2] dmabuf: add DMA_BUF_IOCTL_RW_FILE

On 5/13/25 11:27, wangtao wrote:

Add DMA_BUF_IOCTL_RW_FILE to save/restore data from/to a dma-buf.

Similar approach where rejected before in favor of using udmabuf.

Is there any reason you can't use that approach as well?

Regards, Christian.

Signed-off-by: wangtao tao.wangtao@honor.com

drivers/dma-buf/dma-buf.c | 8 ++++++++ include/linux/dma-buf.h | 3 +++ include/uapi/linux/dma-buf.h | 29 +++++++++++++++++++++++++++++ 3 files changed, 40 insertions(+)

diff --git a/drivers/dma-buf/dma-buf.c b/drivers/dma-buf/dma-buf.c index 5baa83b85515..95d8b0158ffd 100644 --- a/drivers/dma-buf/dma-buf.c +++ b/drivers/dma-buf/dma-buf.c @@ -460,6 +460,7 @@ static long dma_buf_ioctl(struct file *file, struct dma_buf *dmabuf; struct dma_buf_sync sync; enum dma_data_direction direction;

• struct dma_buf_rw_file kfile; int ret;

dmabuf = file->private_data; @@ -504,6 +505,13 @@ static long dma_buf_ioctl(struct file *file, return dma_buf_import_sync_file(dmabuf, (const void __user *)arg); #endif

• case DMA_BUF_IOCTL_RW_FILE:

• if (copy_from_user(&kfile, (void __user *) arg, sizeof(kfile)))
  

• 	return -EFAULT;
  

• if (!dmabuf->ops->rw_file)
  

• 	return -EINVAL;
  

• return dmabuf->ops->rw_file(dmabuf, &kfile);
  

• default: return -ENOTTY; }

diff --git a/include/linux/dma-buf.h b/include/linux/dma-buf.h index 36216d28d8bd..de236ba2094b 100644 --- a/include/linux/dma-buf.h +++ b/include/linux/dma-buf.h @@ -22,6 +22,7 @@ #include <linux/fs.h> #include <linux/dma-fence.h> #include <linux/wait.h> +#include <uapi/linux/dma-buf.h> struct device; struct dma_buf; @@ -285,6 +286,8 @@ struct dma_buf_ops { int (*vmap)(struct dma_buf *dmabuf, struct iosys_map *map); void (*vunmap)(struct dma_buf *dmabuf, struct iosys_map *map);

• int (*rw_file)(struct dma_buf *dmabuf, struct dma_buf_rw_file *file);

}; /** diff --git a/include/uapi/linux/dma-buf.h b/include/uapi/linux/dma-buf.h index 5a6fda66d9ad..ec9164b7b753 100644 --- a/include/uapi/linux/dma-buf.h +++ b/include/uapi/linux/dma-buf.h @@ -167,6 +167,29 @@ struct dma_buf_import_sync_file { __s32 fd; }; +/**

• • struct dma_buf_rw_file - read/write file associated with a dma-buf
• • Userspace can performs a DMA_BUF_IOCTL_BACK to save data from a dma-buf or
• • restore data to a dma-buf.
• */

+struct dma_buf_rw_file {

• /** @flags: Flags indicating read/write for this dma-buf. */
• __u32 flags;
• /** @fd: File descriptor of the file associated with this dma-buf. */
• __s32 fd;
• /** @file_offset: Offset within the file where this dma-buf starts.

• *
  

• *  Offset and Length must be page-aligned for direct I/O.
  

• */
  

• __u64 file_offset;
• /** @buf_offset: Offset within this dma-buf where the read/write starts. */
• __u64 buf_offset;
• /** @buf_len: Length of this dma-buf read/write. */
• __u64 buf_len;

+};

#define DMA_BUF_BASE 'b' #define DMA_BUF_IOCTL_SYNC _IOW(DMA_BUF_BASE, 0, struct dma_buf_sync) @@ -179,4 +202,10 @@ struct dma_buf_import_sync_file { #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) +#define DMA_BUF_RW_FLAGS_OP_MASK (0xFF << 0) +#define DMA_BUF_RW_FLAGS_READ (1 << 0) /* Restore dma-buf data */ +#define DMA_BUF_RW_FLAGS_WRITE (2 << 0) /* Save dma-buf data */ +#define DMA_BUF_RW_FLAGS_DIRECT (1u << 31) /* Direct read/write file */ +#define DMA_BUF_IOCTL_RW_FILE _IOW(DMA_BUF_BASE, 4, struct dma_buf_rw_file)

#endif