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From: Bjorn Helgaas <bjorn.helgaas@hp.com>
To: Len Brown <lenb@kernel.org>
Subject: Re: ISA -> ISA_ (Re: [GIT PATCH] ACPI patches for 2.6.25-rc6)
Date: Wed, 26 Mar 2008 09:56:53 -0600
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Cc: Ingo Molnar <mingo@elte.hu>, Corentin CHARY <corentincj@iksaif.net>,
       Linus Torvalds <torvalds@linux-foundation.org>,
       Andrew Morton <akpm@linux-foundation.org>, linux-acpi@vger.kernel.org,
       linux-kernel@vger.kernel.org, linux-pm@lists.linux-foundation.org
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On Wednesday 26 March 2008 09:32:20 am Len Brown wrote:
> >  /* Here we go */
> > -#define A1x_PREFIX "\\_SB.PCI0.ISA.EC0."
> > +#define A1x_PREFIX "\\_SB.PCI0.ISA_.EC0."
> 
> From an AML point of view, ISA is just as legal as "ISA_"
> The NameString paramter to Device() can be 1 to 4 characters.
> 
> So if this is correct or not depends on what the BIOS programmer
> for the Asus A1x choose to write.  Perhaps Corentin 'Iksaif' CHARY
> can confirm if the driver is working properly on that system.

I'm curious about how this works.  I disassembled the DSDT from
http://bugzilla.kernel.org/show_bug.cgi?id=4773 (I attached the disassembly
at http://bugzilla.kernel.org/attachment.cgi?id=15448&action=view), and
the _PRT contains "_SB" and "ISA" (no trailing underscores):

                Package (0x04)
                {
                    0x000DFFFF, 
                    0x00, 
                    \_SB.PCI0.ISA.LNKA, 
                    0x00
                }

But by the time we get to acpi_pci_irq_add_entry(), we've added the
underscores somewhere (see
http://bugzilla.kernel.org/attachment.cgi?id=15423&action=view):

  0000:00:0d[A] -> \_SB_.PCI0.ISA_.LNKA

I don't know where this happens, but it certainly confused me, and
it seems like it could lead to other bugs.

Bjorn