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    SubjectRe: [PATCH] PnP Changes for 2.5.72
    On Fri, 20 Jun 2003, Andrey Panin wrote:

    > On 171, 06 20, 2003 at 06:55:47AM +0100, Russell King wrote:
    > > On Thu, Jun 19, 2003 at 11:42:49PM +0000, Adam Belay wrote:
    > > > I removed avoid_irq_share because the current pnp code, like the previous, does
    > > > not allow irq sharing. Also it corrupts the device rule structure by replacing
    > > > it with modified values that may not apply after devices are disabled etc.
    > > > Is there a set of conditions I could follow to determine if a serial pnp device
    > > > is capable of irq sharing, and also with which other devices can a capable
    > > > device share an irq? If so, I could have the resource manager handle this type
    > > > of situation when few irqs are available.
    > >
    > > The problem is one of a lack of historical information on why it was
    > > added. The driver itself allows serial ports to share interrupts between
    > > themselves. Maybe tytso knows why the "Rockwell 56K ACF II Fax+Data+Voice
    > > Modem" is unable to share IRQs?
    >
    > It was me who added this crappy quirk.
    >
    > My ELine modem which identified itself "Rockwell 56K ACF II Fax+Data+Voice Modem"
    > was going mad when its IRQ was shared with any device. So I decided to add this
    > quirk.
    >
    > Personally I think that ISA IRQ sharing should be absolutely last resort technic,
    > because ISA bus was never designed to support IRQ sharing sanely. If you have to
    > enable ISA PnP device and do not have enough IRQ, you must print BIG FAT WARNING
    > before doing this. May be kernel config options must be added for brave guys
    > wanting to use ISA IRQ sharing.

    But dumb multiport boards support sharing just fine:

    0: uart:16550A port:3F8 irq:4 baud:1200 tx:6 rx:9587 RTS|CTS|DTR|DSR
    1: uart:16550A port:2F8 irq:3 baud:9600 tx:9 rx:2 brk:2
    2: uart:unknown port:3E8 irq:4
    3: uart:unknown port:2E8 irq:3
    4: uart:16550A port:1A0 irq:5 baud:9600 tx:0 rx:0 CTS
    5: uart:16550A port:1A8 irq:5 baud:9600 tx:0 rx:0
    6: uart:16550A port:1B0 irq:5 baud:9600 tx:0 rx:0
    7: uart:16550A port:1B8 irq:5 baud:9600 tx:0 rx:0

    There's more to it than just "it doesn't work." I note that 2.5.70 still
    sets the NIC and AHA1540 to the same irq, while 2.4.18 doesn't. I gave up
    on that, I can't change the hardware (specialty hardware) so I run 2.4
    kernels. Someday I'll fight with it.

    --
    bill davidsen <davidsen@tmr.com>
    CTO, TMR Associates, Inc
    Doing interesting things with little computers since 1979.
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