Extend write_buf documentation

diff --git a/include/fuse_lowlevel.h b/include/fuse_lowlevel.h
index 3cc9db574518fe4c4e34fb2bd39d1ad8ed8104a8..32908cb7677d028eeb35146ed131b22026241c39 100644 (file)
--- a/include/fuse_lowlevel.h
+++ b/include/fuse_lowlevel.h
@@ -932,6 +932,11 @@ struct fuse_lowlevel_ops {
         * kernel supports splicing from the fuse device, then the
         * data will be made available in pipe for supporting zero
         * copy data transfer.
+         *
+         * buf->count is guaranteed to be one (and thus buf->idx is
+         * always zero). The write_buf handler must ensure that
+         * bufv->off is correctly updated (reflecting the number of
+         * bytes read from bufv->buf[0]).
         *
         * Introduced in version 2.9
         *