[PATCH v3 8/9] ACPI: arm64: use an arch-specific ACPI _OSI method and ACPI blacklist

[Rafael J. Wysocki]

On Monday, March 02, 2015 12:00:21 PM Al Stone wrote:
> On 03/02/2015 10:29 AM, Will Deacon wrote:
> > Hi Al,
> > 
> > On Wed, Feb 25, 2015 at 12:36:24AM +0000, al.stone at linaro.org wrote:
> >> diff --git a/arch/arm64/kernel/acpi-blacklist.c b/arch/arm64/kernel/acpi-blacklist.c
> >> new file mode 100644
> >> index 0000000..1be6a56
> >> --- /dev/null
> >> +++ b/arch/arm64/kernel/acpi-blacklist.c
> >> @@ -0,0 +1,20 @@
> >> +/*
> >> + *  ARM64 Specific ACPI Blacklist Support
> >> + *
> >> + *  Copyright (C) 2015, Linaro Ltd.
> >> + *	Author: Al Stone <al.stone at linaro.org>
> >> + *
> >> + *  This program is free software; you can redistribute it and/or modify
> >> + *  it under the terms of the GNU General Public License version 2 as
> >> + *  published by the Free Software Foundation.
> >> + */
> >> +
> >> +#define pr_fmt(fmt) "ACPI: " fmt
> >> +
> >> +#include <linux/acpi.h>
> >> +
> >> +/* The arm64 ACPI blacklist is currently empty.  */
> >> +int __init acpi_blacklisted(void)
> >> +{
> >> +	return 0;
> >> +}
> >> diff --git a/arch/arm64/kernel/acpi-osi.c b/arch/arm64/kernel/acpi-osi.c
> >> new file mode 100644
> >> index 0000000..bb351f4
> >> --- /dev/null
> >> +++ b/arch/arm64/kernel/acpi-osi.c
> >> @@ -0,0 +1,25 @@
> >> +/*
> >> + *  ARM64 Specific ACPI _OSI Support
> >> + *
> >> + *  Copyright (C) 2015, Linaro Ltd.
> >> + *	Author: Al Stone <al.stone at linaro.org>
> >> + *
> >> + *  This program is free software; you can redistribute it and/or modify
> >> + *  it under the terms of the GNU General Public License version 2 as
> >> + *  published by the Free Software Foundation.
> >> + */
> >> +
> >> +#define pr_fmt(fmt) "ACPI: " fmt
> >> +
> >> +#include <linux/acpi.h>
> >> +
> >> +/*
> >> + * Consensus is to deprecate _OSI for all new ACPI-supported architectures.
> >> + * So, for arm64, reduce _OSI to a warning message, and tell the firmware
> >> + * nothing of value.
> >> + */
> >> +u32 acpi_osi_handler(acpi_string interface, u32 supported)
> >> +{
> >> +	pr_warn("_OSI was called, but is deprecated for this architecture.\n");
> >> +	return false;
> >> +}
> > 
> > This kinda feels backwards to me. If _OSI is going away, then the default
> > should be "the architecture doesn't need to do anything", rather than have
> > new architectures defining a bunch of empty, useless stub code.
> > 
> > Anyway we could make this the default in core code and have architectures
> > that *do* want _OSI override that behaviour, instead of the other way around?
> > 
> > Cheers,
> > 
> > Will
> > 
> 
> We could do that; I personally don't have a strong preference either way,
> so I'm inclined to make it whatever structure Rafael thinks is proper since
> it affects ACPI code most.  That being said, the current patch structure
> made sense to me since it wasn't distorting existing code much -- and given
> the pure number of x86/ia64 machines vs ARM machines using ACPI, that seemed
> the more cautious approach.
> 
> @Rafael: do you have an opinion/preference?

My preference is to avoid changes in the existing code at least for the time
being.  Especially if the changes in question are going to affect ia64, unless
you have an Itanium machine where you can readily test those, that is. :-)


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