This calculates a proper timeout value for blocking writes on the
given serial port, for the given number of bytes. Timeout is based
on a fixed 10ms OS overhead, baud rate, data bits and stop bits.
Set this new parameter to 0 (no timeout) at every call site. This is
consistent with previous behaviour, so cannot cause any regressions.
Waiting forever for a serial operation is clearly always wrong. Without
specific knowledge of each device and driver however, I can't choose
appropriate timeouts for each call. The maintainers of these drivers
will need to do so, and also add appropriate handling of timeouts.
When this commit is merged, a bug should be entered for each driver
that is touched by it.
This code implements its own waiting based on baudrate, so the read itself
should be nonblocking. In general it will have been already, since drivers
almost universally use the SERIAL_NONBLOCK flag.
Uwe Hermann
Aurelien Jacobs
Uffe Jakobsen
Bert Vermeulen
Martin Ling