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    SubjectBogus serial port ttyS02

    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.

    This is not exactly a new problem, and it happens with (and is not limited to)
    both 2.4.21 and 2.6.0-test3. System is a PPC box (CHRP LongTrail) with a
    National Semiconductor PC78308VUL SuperI/O, which has 2 internal 16550As.

    Anyone with a clue? I know nothing about serial chip probing.

    Ah, I still have some old dmesg outputs for that machine in my local CVS repo:

    2.2.7: OK
    2.3.18: OK
    2.3.22: OK
    2.3.42: not OK
    2.3.47: not OK
    2.3.48: not OK
    2.3.50: not OK
    2.3.51: not OK
    2.3.99-pre3: not OK
    2.4.0-test1: not OK
    2.4.0-test1-ac7: OK
    2.4.0-test1-ac10: OK
    2.4.0-test11: not OK
    2.4.0-test13-pre3: not OK
    2.4.0-prerelease-ac5: not OK
    2.4.0: not OK
    2.4.1-pre2: not OK
    2.4.1-pre10: not OK
    2.4.1: not OK

    So the problem was introduced between 2.3.22 and 2.3.42, and temporarily solved
    in 2.4.0-test1-ac7 and 2.4.0-test1-ac10.

    2.4.0-test1 has serial driver version 4.93 (2000-03-20)
    2.4.0-test1-ac7 and 2.4.0-test1-ac10 have version 5.01 (2000-05-29)
    2.4.0-test11 has version 5.02 (2000-08-09)

    All are with MANY_PORTS SHARE_IRQ SERIAL_PCI enabled. Looking at the diffs
    between 2.4.0-test1 and 2.4.0-test1-ac7, and 2.4.0-test1-ac7 and 2.4.0-test11
    I couldn't find anything suspicious.



    Geert Uytterhoeven -- There's lots of Linux beyond ia32 --

    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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