Hi Bjorn,
On Wed, 25 Jul 2007 07:16:44 -0600 Bjorn Helgaas <[email protected]> wrote:
> On Wednesday 25 July 2007 01:45:54 am Sébastien Dugué wrote:
> > looks like the commit was dropped, nevertheless here is some more info
> > to try and understand what may be going on so it may benefit the posterity ;-)
>
> Thank you very much.
>
> Your machine does indeed describe both UARTs in ACPI, and the PNP probe
> finds them correctly. The only wrinkle is that the PNP probe names the
> ports in the order they appear in the ACPI namespace, and your firmware
> has them "backwards":
>
> Device (COMB)
> {
> Name (_HID, EisaId ("PNP0501"))
> Name (_DDN, "COM2")
> Name (_UID, 0x02)
>
> Device (COMA)
> {
> Name (_HID, EisaId ("PNP0501"))
> Name (_DDN, "COM1")
> Name (_UID, 0x01)
Yes, that's what I thought was weird in the DSDT, but thought the PnP layer
would map those devices according to UID or at least DDN. It seems that's
not the case.
>
> There's nothing illegal about this, but with the current PNPACPI,
> it causes the names to be reversed. The blind probe tries 0x3f8
> first, and names that ttyS0. But the PNP probe, using the namespace
> order, finds the "COM2" port at 0x2f8 first:
>
> 00:0b: ttyS0 at I/O 0x2f8 (irq = 3) is a 16550A
> 00:0c: ttyS1 at I/O 0x3f8 (irq = 4) is a 16550A
Oh I see, didn't notice this though.
>
> So I think your serial console would work without "legacy_serial.force"
> if you used "console=ttyS1" instead of "console=ttyS0". But you
> shouldn't have to do that, of course.
Will try ttyS1 just to confirm...
Waiting for reboot...
OK boots fine with the serial console fully operational again.
>
> The _DDN is a "DOS device name", and the _UID is a "logical device ID
> that does not change across reboots." Both are optional, and PNPACPI
> ignores them. But maybe we could change PNPACPI to sort by them if
> they are present. I'll think about this a bit.
That would be nice, but I wish you good luck with all those
crappy BIOSes out there.
Thanks,
Sébastien.
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