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SubjectRe: PNPACPI probes serial twice, messes up serial console
Bjorn Helgaas (on Wed, 21 Mar 2007 10:35:38 -0600) wrote:
>On Tuesday 20 March 2007 08:32, Bjorn Helgaas wrote:
>> On Tuesday 20 March 2007 00:46, Keith Owens wrote:
>> > Booting with 'console=tty console=ttyS0,9600'. The serial console on
>> > ttyS0 (0x3f8, irq 4) is probed twice, once from serial8250_init() and
>> > again from serial_pnp_probe().
>> I played with this last summer, but was too timid to finish it
>> and post it. My plan was to remove the legacy SERIAL_PORT_DFNS,
>> make platform devices for them, and only register the platform
>> devices in the absence of PNP.
>> My motivation at the time was to prevent 8250 from claiming IRDA
>> devices that happened to live at legacy UART addresses. I also
>> wanted to make IRDA (smsc-ircc2 in my case) smart enough to use
>> PNP to locate its devices, since 8250 would no longer claim them.
>> Here's the dusty patch (against 2.6.18-rc1-mm2). If it seems
>> like a reasonable thing to do, I can update it, polish it up,
>> add a changelog, and post it.
>Keith, does this patch help? Russell didn't complain about it, so
>if it fixes your problem, maybe we could put it in -mm and see if
>it breaks anything else.

The aim of the patch looks sensible, but it will not compile for
2.6.21-rc4. 8250_x86.c tests pnp_platform_devices, which does not
exist. Also the combination of CONFIG_SERIAL_8250_X86=y and
CONFIG_SERIAL_8250_PNP=m would result in 8250_x86.o being built into
vmlinux but referring to serial8250_nopnp in module 8250_pnp.o, kernel
to module references are tricky.

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