Re: [patch 7/7] acpi: remove old blacklist entries

[Len Brown <lenb@kernel.org>]

On Wed, 17 Feb 2010, Matthew Garrett wrote:

> On Tue, Feb 16, 2010 at 09:49:03PM -0500, Len Brown wrote:
> 
> > In the future, I'll consider deleting the "acpi=ht"
> > option all together, and the blacklist with it,
> > but such changes are always harder than expected.
> 
> We seem to have no good history of where these blacklist entries came 
> from, and we know that at least one of them is actively harmful. Perhaps 
> replace them with a debug statement on affected machines telling people 
> what they need to pass to restore the blacklist behaviour, and to let us 
> know if it's necessary?

Actually, it wasn't actively harmful until we broke "acpi=ht".
Indeed, it was actively helpful in pointing out that regression:-)

Yes, I think that a warning for a release or so before deleting
some of these entries would make sense -- good idea.

Re: history...
unfortunately old-2.6-bkcvs history is nearly useless,
but bkbits still seems to work.

It shows I pulled this DMI list from Linux-2.4 to Linux-2.6
on 2003-08-09, and that it originally came from Suse:

"pull DMI blacklist from UnitedLinux via 2.4 for disabling ACPI on bad 
BIOS boxes.  This also sets ACPI_BLACKLIST_CUTOFF_YEAR = 2001"

http://linux.bkbits.net:8080/linux-2.6.11-stable/arch/i386/kernel/dmi_scan.c?PAGE=diffs&REV=3f35b565a8XFxBnmR2yf-97PQRqW3Q

I think that move was a short term good idea,
but a long term bad idea.

It looks like we have added no forc_acpi_ht entries since 2003,
but we have deleted a bunch of them.  So it may indeed be time
for the force_acpi_ht, and perhaps the "acpi=ht" option to go.

The other entries in today's acpi_dmi_table[] are less clear
and should probably be modified only with some care...

I'll spin a patch for the acpi=ht part.

thanks,
-Len Brown, Intel Open Source Technology Center