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    SubjectRe: wrong number of serial port detected
    >From: Bjorn Helgaas <>
    >To: "Jason Dravet" <>
    >Subject: Re: wrong number of serial port detected
    >Date: Fri, 9 Dec 2005 12:54:44 -0700
    >On Friday 09 December 2005 7:37 am, Jason Dravet wrote:
    > > The question I have
    > > is with all of this plug and play stuff in our PCs shouldn't it be
    > > to get the correct number of ports, ask the bios or the pci bus or
    > > something?
    >Yes. ACPI (or even PNPBIOS) should tell us about all the "legacy"
    >ports, and PCI or other bus enumeration should tell us about all the
    >So in theory, if we have some flavor of PNP, we should be able to
    >ignore all the compiled-in stuff in SERIAL_PORT_DFNS, which is what
    >leads to the duplicate port detection. I've considered doing that
    >(and ia64 already does it), but it would almost certainly break
    >systems because of BIOS bugs, so I'm not sure it's worth the risk.

    I agree that breaking things is bad, but it would be interesting to see what
    would happen and if anyone complains. A gut feeling is that very few people
    use more than the two serial ports that come on their motherboards. Where I
    work out of the 2,500 PCs on campus, only 3 or 4 PCs actually use a serial
    port. I think this would be a good survey for slashdot. I don't use the
    serial ports on my PCs. I do use the serial ports on my servers. The
    serial ports on the servers connect to a digi terminal server. One serial
    port is the management interface to the server, the other is setup for
    serial login.

    The reason I started this thread is because I wanted to know why/how I was
    seeing 32 serial ports in /dev when I have 0 enabled on my PC and I have 2
    serial ports on my servers. Thanks to the responses I have a better
    understanding of what is going on.

    >Having all the extra /dev/ttyS entries is a little different problem.
    >That is basically so "setserial /dev/ttySx" can be used to work around
    >the fact that the serial driver doesn't know about all existing devices.
    >If it did, setserial should be superfluous. Maybe there'd be a way to
    >implement that functionality via sysfs and get rid of the extra
    >/dev/ttyS entries. That'd be kind of cool.

    sysfs is way outside my area of understanding. Anything that moves to a
    more accurate /dev directory is good in my book.


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