+ return relay_file_read_subbufs(filp, ppos, subbuf_read_actor,
+ NULL, &desc);
+}
+
+static void relay_consume_bytes(struct rchan_buf *rbuf, int bytes_consumed)
+{
+ rbuf->bytes_consumed += bytes_consumed;
+
+ if (rbuf->bytes_consumed >= rbuf->chan->subbuf_size) {
+ relay_subbufs_consumed(rbuf->chan, rbuf->cpu, 1);
+ rbuf->bytes_consumed %= rbuf->chan->subbuf_size;
+ }
+}
+
+static void relay_pipe_buf_release(struct pipe_inode_info *pipe,
+ struct pipe_buffer *buf)
+{
+ struct rchan_buf *rbuf;
+
+ rbuf = (struct rchan_buf *)page_private(buf->page);
+ relay_consume_bytes(rbuf, buf->private);
+}
+
+static const struct pipe_buf_operations relay_pipe_buf_ops = {
+ .can_merge = 0,
+ .map = generic_pipe_buf_map,
+ .unmap = generic_pipe_buf_unmap,
+ .confirm = generic_pipe_buf_confirm,
+ .release = relay_pipe_buf_release,
+ .steal = generic_pipe_buf_steal,
+ .get = generic_pipe_buf_get,
+};
+
+static void relay_page_release(struct splice_pipe_desc *spd, unsigned int i)
+{
+}
+
+/*
+ * subbuf_splice_actor - splice up to one subbuf's worth of data
+ */
+static ssize_t subbuf_splice_actor(struct file *in,
+ loff_t *ppos,
+ struct pipe_inode_info *pipe,
+ size_t len,
+ unsigned int flags,
+ int *nonpad_ret)
+{
+ unsigned int pidx, poff, total_len, subbuf_pages, nr_pages;
+ struct rchan_buf *rbuf = in->private_data;
+ unsigned int subbuf_size = rbuf->chan->subbuf_size;
+ uint64_t pos = (uint64_t) *ppos;
+ uint32_t alloc_size = (uint32_t) rbuf->chan->alloc_size;
+ size_t read_start = (size_t) do_div(pos, alloc_size);
+ size_t read_subbuf = read_start / subbuf_size;
+ size_t padding = rbuf->padding[read_subbuf];
+ size_t nonpad_end = read_subbuf * subbuf_size + subbuf_size - padding;
+ struct page *pages[PIPE_BUFFERS];
+ struct partial_page partial[PIPE_BUFFERS];
+ struct splice_pipe_desc spd = {
+ .pages = pages,
+ .nr_pages = 0,
+ .partial = partial,
+ .flags = flags,
+ .ops = &relay_pipe_buf_ops,
+ .spd_release = relay_page_release,
+ };
+ ssize_t ret;
+
+ if (rbuf->subbufs_produced == rbuf->subbufs_consumed)
+ return 0;
+
+ /*
+ * Adjust read len, if longer than what is available
+ */
+ if (len > (subbuf_size - read_start % subbuf_size))
+ len = subbuf_size - read_start % subbuf_size;