ial case, according to the standard:

"Before any action described below is taken, and if nbyte is zero,
the read() function may detect and return errors as described below.
In the absence of errors, or if error detection is not performed,
the read() function shall return zero and have no other results."

Signed-off-by: David Herrmann <dh.herrmann@googlemail.com>
Signed-off-by: Dmitry Torokhov <dtor@mail.ru>