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    SubjectRe: commit 7e92b4fc34 - x86, serial: convert legacy COM ports to platform devices - broke my serial console
    Andrew Morton wrote:
    > Well I queued up a tentative revert patch but then I re-read the changlog:
    >
    > x86, serial: convert legacy COM ports to platform devices
    >
    > Make x86 COM ports into platform devices and don't probe for them
    > if we have PNP.
    >
    > This prevents double discovery, where a device was found both by
    > the legacy probe and by 8250_pnp, e.g.,
    >
    > serial8250: ttyS0 at I/O 0x3f8 (irq = 4) is a 16550A
    > 00:02: ttyS0 at I/O 0x3f8 (irq = 4) is a 16550A

    If this actually causes a problem, then the drivers are buggy. We have
    standard APIs for checking this stuff...

    Turning off legacy serial probing is just a bandaid, the resource bug is
    still there [by definition, if double-probing problems exist].


    > This also means IRDA devices without a UART PNP ID will no longer be
    > claimed by the serial driver, which might require changes in IRDA
    > drivers and administration.

    This was completely unaddressed, I presume?


    > In addition to this patch, you may need to configure a setserial init
    > script, e.g., /etc/init.d/setserial, so it doesn't poke legacy UART
    > stuff back in. On Debian, "dpkg-reconfigure setserial" with the "kernel"
    > option does this.

    So this patch breaks some userspace too?


    > To force the old legacy probe behavior even when we have PNPBIOS or
    > ACPI, load the new legacy_serial module (or build 8250 static) with
    > the "legacy_serial.force" option.
    >
    > So 7e92b4fc345f5b6f57585fbe5ffdb0f24d7c9b26 fixed a bunch of longstanding
    > nasties while breaking Sebastien's machine (at least).
    >
    > We of course want the best of both worlds here, so I'll keep the revert
    > patch in -mm for a while, see what happens. Although I can't immediately
    > see any way in which this can be fixed...

    I see VERY few positives, a whole lot of trouble, and a couple band-aids.

    Jeff


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