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SubjectRe: Bogus serial port ttyS02
On Wed, 13 Aug 2003, Richard B. Johnson wrote:
> On Wed, 13 Aug 2003, Geert Uytterhoeven wrote:
> > Linux always finds 3 serial ports instead of 2:
> >
> > | ttyS00 at 0x03f8 (irq = 4) is a 16550A
> > | ttyS01 at 0x02f8 (irq = 3) is a 16550A
> > | ttyS02 at 0x03e8 (irq = 4) is a 16450
> >
> > The last one is bogus.
>
> First, this looks like ix86 stuff, not m68k. Drivers for ix86

It's PPC, not m68k. Both PReP and CHRP have PC-style serial ports.

> machines probe the de facto addresses for up to a maximum of
> 4 8250-type UARTS. Those addresses are:
>
> (0) 0x3f8
> (1) 0x2f8
> (2) 0x3e8
> (3) 0x328
>
> (from the Phoenix SYSTEM BIOS book)
>
> Usually, there are several bits that are permanently 0 in
> some of the registers. This is used to "positively" identify
> the chip. Note that many IR devices are also connected
> to 8250-type UARTS.
>
> I would guess that you have two serial ports, plus another
> UART that's used for IR (maybe a IR keyboard???).

No, the Super I/O has only two serial ports, of which one can be used for IRDA.

> You can do `od /dev/ttyS2` from the root account and see
> what happends.

Nothing, it just waits for data. The same for `echo hello > /dev/ttyS2'. So the
serial driver things it has to wait to accept/send data.
Gr{oetje,eeting}s,
Geert

--
Geert Uytterhoeven -- There's lots of Linux beyond ia32 -- geert@linux-m68k.org

In personal conversations with technical people, I call myself a hacker. But
when I'm talking to journalists I just say "programmer" or something like that.
-- Linus Torvalds

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