libhw_generic: io.h: Clarify that sum lenghts of iovecs must not be 0

1 files changed, 6 insertions, 0 deletions

diff --git a/libhw_generic/include/libhw/generic/io.h b/libhw_generic/include/libhw/generic/io.h
index 6adce8c..96680bb 100644
--- a/libhw_generic/include/libhw/generic/io.h
+++ b/libhw_generic/include/libhw/generic/io.h
@@ -58,6 +58,8 @@ void io_slice_wr_to_duplex(struct duplex_iovec *dst, const struct iovec *src, in
 /**
  * Return bytes-read on success, 0 on EOF, -errno on error; a short
  * read is *not* an error.
+ *
+ * It is invalid to call readv when the sum length of iovecs is 0.
  */
 #define io_reader_LO_IFACE \
 	LO_FUNC(ssize_t, readv, const struct iovec *iov, int iovcnt)
@@ -71,6 +73,8 @@ LO_INTERFACE(io_reader);
  *
  * Writes are *not* guaranteed to be atomic, so if you have concurrent
  * writers then you should arrange for a mutex to protect the writer.
+ *
+ * It is invalid to call writev when the sum length of iovecs is 0.
  */
 #define io_writer_LO_IFACE \
 	LO_FUNC(ssize_t, writev, const struct iovec *iov, int iovcnt)
@@ -100,6 +104,8 @@ LO_INTERFACE(io_bidi_closer);
 /**
  * Return bytes-read and bytes-written on success, -errno on error; a
  * short read/write *is* an error.
+ *
+ * It is invalid to call readwritev when the sum length of iovecs is 0.
  */
 #define io_duplex_readwriter_LO_IFACE \
 	LO_FUNC(void, readwritev, const struct duplex_iovec *iov, int iovcnt)