NAME

cy — Cyclades Cyclom-{4, 8, 16}Y asynchronous comms board device driver

SYNOPSIS

cy0 at isa? iomem 0xd4000 irq 12
cy* at pci?

DESCRIPTION

This driver provides an interface to Cyclades Cyclom-4Y, Cyclom-8Y and Cyclom-16Y asynchronous multiport serial boards. These boards are based around Cirrus Logic CD1400 communication controllers.

The device minor numbers for this driver are encoded as follows:

    d c c u u u u u	- bits in the minor device number

    bits    meaning
    ----    -------
    uuuuu   physical serial line (i.e., unit) to use
		0-7 on a cyclom-8Y, 0-15 on a cyclom-16Y

    cc      card number

    d       dial-out flag

DIAGNOSTICS

cy0: tty input queue overflow

Incoming characters have been discarded due to a buffer overflow. This is caused by the process in control of the device not read(2)'ing characters fast enough.

cy0: receive fifo overrun

Incoming characters have been discarded due to a CD1400 channel overrun. This is caused by interrupts not being serviced sufficiently quickly to prevent the 12 byte receive FIFO on a serial channel from overflowing. Reducing the value of the RxFifoThreshold #define from 8 to something smaller may help slow machines avoid this problem. The driver must have been compiled with the LogOverruns option defined (the default) in order for this condition to be logged.

SEE ALSO

com(4), intro(4), isa(4), pci(4), termios(4), tty(4)

HISTORY

Some ideas for the architecture of this driver's two-layer processing model were derived from the fas 2.10 driver by Uwe Doering <gemini@geminix.in-berlin.de> and the high-performance com driver by Bruce Evans <bde@kralizec.zeta.org.au>.

This work was made possible through the donation of a Cyclom-8Y board by the manufacturer, Cyclades Corporation. However, neither Cyclades nor the author make any warranties regarding this software, nor guarantees of support.

AUTHORS

The driver was written by Andrew Herbert <andrew@werple.apana.org.au>.

BUGS

There is currently no BREAK handling - breaks are ignored. There is no support for bad-character reporting, except via PARMRK. The Cyclom-[48]Y boards do not listen to the RTS signal for receiver flow control. FIFO overruns are only logged when the termios IGNPAR setting is enabled.