linux-kernel - Re: [RFC 1/2] ACPI: activate&export acpi_os_get_physical

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Date:	Fri, 01 May 2015 03:45:52 +0200
From:	"Rafael J. Wysocki" <rjw@...ysocki.net>
To:	Darren Hart <dvhart@...radead.org>,
	Matthew Garrett <mjg59@...f.ucam.org>
Cc:	Kast Bernd <kastbernd@....de>, corentin.chary@...il.com,
	lenb@...nel.org, linux-acpi@...r.kernel.org,
	linux-kernel@...r.kernel.org, acpi4asus-user@...ts.sourceforge.net,
	platform-driver-x86@...r.kernel.org
Subject: Re: [RFC 1/2] ACPI: activate&export acpi_os_get_physical_address

On Friday, May 01, 2015 03:32:29 AM Rafael J. Wysocki wrote:
> On Thursday, April 30, 2015 11:10:25 AM Darren Hart wrote:
> > On Wed, Apr 22, 2015 at 04:12:24PM +0200, Kast Bernd wrote:
> > > acpi_os_get_physical_address will be needed by an acpi driver (asus-wmi.c).
> > > Additionally it could  be used by dell-laptop.c instead of directly calling virt_to_phys.
> > > 
> > > acpi_os_get_physical_address gets exported and ACPI_FUTURE_USAGE is removed
> > > 
> > 
> > Hrm, well... this doesn't get rid of virt_to_phys, it just wraps it really. I'm
> > not sure that makes this any more acceptable than the original from Felipe - but
> > that's not my call.
> 
> Use virt_to_phys() if you need to.
> 
> This one is in case ACPICA needs to get the virtual-to-physical mapping (hence
> ACPI_FUTURE_USAGE).

More to the point, the reason why virt_to_phys() needs to be used in patch [2/2]
seems to be a nasty hack in the ASUS AML that pretty much expects us to provide
the physical address as an argument.

And I don't really understand the Matthew's comment regarding limiting
operation regions to system memory.  This is about a specific operation
region (which BTW only seems to be used as a means to access system memory
at the location pointed to by the arg) in that particular method.

Matthew?


-- 
I speak only for myself.
Rafael J. Wysocki, Intel Open Source Technology Center.
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