On 6/3/25 11:52, wangtao wrote:

First determine if dmabuf reads from or writes to the file. Then call exporter's rw_file callback function.

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

drivers/dma-buf/dma-buf.c | 32 ++++++++++++++++++++++++++++++++ include/linux/dma-buf.h | 16 ++++++++++++++++ 2 files changed, 48 insertions(+)

diff --git a/drivers/dma-buf/dma-buf.c b/drivers/dma-buf/dma-buf.c index 5baa83b85515..fc9bf54c921a 100644 --- a/drivers/dma-buf/dma-buf.c +++ b/drivers/dma-buf/dma-buf.c @@ -523,7 +523,38 @@ static void dma_buf_show_fdinfo(struct seq_file *m, struct file *file) spin_unlock(&dmabuf->name_lock); } +static ssize_t dma_buf_rw_file(struct dma_buf *dmabuf, loff_t my_pos,

• struct file *file, loff_t pos, size_t count, bool is_write)

+{

• if (!dmabuf->ops->rw_file)

• return -EINVAL;
  

• if (my_pos >= dmabuf->size)

• count = 0;
  

• else

• count = min_t(size_t, count, dmabuf->size - my_pos);
  

• if (!count)

• return 0;
  

• return dmabuf->ops->rw_file(dmabuf, my_pos, file, pos, count, is_write);

+}

+static ssize_t dma_buf_copy_file_range(struct file *file_in, loff_t pos_in,

• struct file *file_out, loff_t pos_out,
• size_t count, unsigned int flags)

+{

• if (is_dma_buf_file(file_in) && file_out->f_op->write_iter)

• return dma_buf_rw_file(file_in->private_data, pos_in,
  

• 		file_out, pos_out, count, true);
  

• else if (is_dma_buf_file(file_out) && file_in->f_op->read_iter)

• return dma_buf_rw_file(file_out->private_data, pos_out,
  

• 		file_in, pos_in, count, false);
  

• else

• return -EINVAL;
  

+}

static const struct file_operations dma_buf_fops = {

• .fop_flags = FOP_MEMORY_FILE, .release = dma_buf_file_release, .mmap = dma_buf_mmap_internal, .llseek = dma_buf_llseek,

@@ -531,6 +562,7 @@ static const struct file_operations dma_buf_fops = { .unlocked_ioctl = dma_buf_ioctl, .compat_ioctl = compat_ptr_ioctl, .show_fdinfo = dma_buf_show_fdinfo,

• .copy_file_range = dma_buf_copy_file_range,

}; /* diff --git a/include/linux/dma-buf.h b/include/linux/dma-buf.h index 36216d28d8bd..d3636e985399 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 +286,21 @@ struct dma_buf_ops { int (*vmap)(struct dma_buf *dmabuf, struct iosys_map *map); void (*vunmap)(struct dma_buf *dmabuf, struct iosys_map *map);

• /**

• * @rw_file:
  

• *
  

• * If an Exporter needs to support Direct I/O file operations, it can
  

• * implement this optional callback. The exporter must verify that no
  

• * other objects hold the sg_table, ensure exclusive access to the
  

• * dmabuf's sg_table, and only then proceed with the I/O operation.
  

Explain why and not what. E.g. something like "Allows direct I/O between this DMA-buf and the file".

Completely drop mentioning the sg_table, that is irrelevant. Exclusive access depends on how the exporter implements the whole thing.

Regards, Christian.

• *
  

• * Returns:
  

• *
  

• * 0 on success or a negative error code on failure.
  

• */
  

• ssize_t (*rw_file)(struct dma_buf *dmabuf, loff_t my_pos,

• struct file *file, loff_t pos, size_t count, bool is_write);
  

}; /**