Fix pts(4) error codes when slave device is closed.

Unlike pre-MPSAFE TTY, the pts(4) driver always returned ENXIO when a
read() or write() was performed on a pseudo-terminal master device when
the slave device was not opened. The old implementation had different
semantics:

- When the slave device had not been opened yet, read() and write() just
  blocked.
- When the slave device had been closed, a read() call would return 0
  bytes length.
- When the slave device had been closed, a write() call would return
  EIO.

Change the new implementation to return 0 and EIO as well. We don't
implement the first rule, but I suspect this is not needed, because
routines like openpty() also open the slave device node. posix_openpt()
users also do similar things.

Reported by:	rink
Tested by:	rink

0 files changed, 0 insertions, 0 deletions