Re: [PATCH] Stop pmac_zilog from abusing 8250's device numbers.

David Woodhouse
2007-04-03T23:29:18Z

On Wed, 2007-04-04 at 09:14 +1000, Paul Mackerras wrote:
> Sigh. I guess this is inevitable, but IMNSHO this exposes a weakness
> in our serial subsystem.
>
> The problem is that this means that a user has to know "oh, the serial
> port on my computer is implemented with a Z85C30 chip, therefore it's
> /dev/ttyPZ0 not /dev/ttyS0, like it would be if the designers had used
> a 16C550".
>
> Plus I'm sure this is going to mean that people using gui ppp dialers
> on powermacs will suddenly find that the gui can no longer find their
> serial port and they have no idea why.

> Why should a user know or care about that? It really should be "it's
> the built-in serial port on my computer therefore it's /dev/ttyS0".

I agree to a certain extent -- but then again, why should a user know or
care about the name /dev/ttyS0 _either_? A GUI PPP dialer should be
listing the available serial ports in the system whatever their names
are.

And nobody _forces_ you to use the name ttyPZ0. If you really want, you
can call it ttyS0.... just mknod /dev/ttyS0 204 192

You could even have udev rules which share the /dev/ttyS$N namespace
between _all_ kinds of serial ports, if you really want to.

Abusing the 8250 device numbers prevents the 8250 module from being
loaded at the same time as pmac_zilog, and means you can't have both
internal port and PCMCIA or PCI 8250 ports active at the same time.

--
dwmw2