Date:	Wed, 04 Feb 2015 14:50:47 +0100
From:	"Rafael J. Wysocki" <rjw@...ysocki.net>
To:	al.stone@...aro.org
Cc:	lenb@...nel.org, catalin.marinas@....com, will.deacon@....com,
	robert.moore@...el.com, tony.luck@...el.com, fenghua.yu@...el.com,
	linux-ia64@...r.kernel.org, linux-kernel@...r.kernel.org,
	linux-acpi@...r.kernel.org, devel@...ica.org,
	linux-arm-kernel@...ts.infradead.org, linaro-acpi@...ts.linaro.org,
	linaro-kernel@...ts.linaro.org, patches@...aro.org
Subject: Re: [PATCH v2 1/5] ACPI: move acpi_os_handler() so it can be made arch-dependent later

On Tuesday, February 03, 2015 05:21:40 PM al.stone@...aro.org wrote:
> From: Al Stone <al.stone@...aro.org>
> 
> In order to deprecate the use of _OSI for arm64 or other new architectures,
> we need to make the default handler something we can change for various
> platforms.  This patch moves the definition of acpi_osi_handler() -- the
> function used by ACPICA as a callback for evaluating _OSI -- into a separate
> file.  Subsequent patches will change which files get built so that we can
> then build the version of _OSI we need for a particular architecture.
> 
> There is no functional change.
> 
> Signed-off-by: Al Stone <al.stone@...aro.org>
> ---
>  drivers/acpi/Makefile |   2 +-
>  drivers/acpi/osi.c    | 100 ++++++++++++++++++++++++++++++++++++++++++++++++++
>  drivers/acpi/osl.c    |  24 ------------
>  include/linux/acpi.h  |   1 +
>  4 files changed, 102 insertions(+), 25 deletions(-)
>  create mode 100644 drivers/acpi/osi.c
> 
> diff --git a/drivers/acpi/Makefile b/drivers/acpi/Makefile
> index c346011..df348b3 100644
> --- a/drivers/acpi/Makefile
> +++ b/drivers/acpi/Makefile
> @@ -18,7 +18,7 @@ obj-y				+= acpi.o \
>  					acpica/
>  
>  # All the builtin files are in the "acpi." module_param namespace.
> -acpi-y				+= osl.o utils.o reboot.o
> +acpi-y				+= osl.o utils.o reboot.o osi.o
>  acpi-y				+= nvs.o
>  
>  # Power management related files
> diff --git a/drivers/acpi/osi.c b/drivers/acpi/osi.c
> new file mode 100644
> index 0000000..fff2b0c
> --- /dev/null
> +++ b/drivers/acpi/osi.c
> @@ -0,0 +1,100 @@
> +/*
> + *  osi.c - _OSI implementation (moved from drivers/acpi/osl.c)
> + *
> + *  Copyright (C) 2000       Andrew Henroid
> + *  Copyright (C) 2001, 2002 Andy Grover <andrew.grover@...el.com>
> + *  Copyright (C) 2001, 2002 Paul Diefenbaugh <paul.s.diefenbaugh@...el.com>
> + *  Copyright (c) 2008 Intel Corporation
> + *   Author: Matthew Wilcox <willy@...ux.intel.com>
> + *
> + * ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
> + *
> + *  This program is free software; you can redistribute it and/or modify
> + *  it under the terms of the GNU General Public License as published by
> + *  the Free Software Foundation; either version 2 of the License, or
> + *  (at your option) any later version.
> + *
> + *  This program is distributed in the hope that it will be useful,
> + *  but WITHOUT ANY WARRANTY; without even the implied warranty of
> + *  MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
> + *  GNU General Public License for more details.

Nit: The street address of the FSF is not really useful here.  What if they move? :-)

> + *
> + *  You should have received a copy of the GNU General Public License
> + *  along with this program; if not, write to the Free Software
> + *  Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA  02111-1307  USA
> + *
> + * ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
> + *
> + */
> +
> +#include <linux/acpi.h>
> +
> +#define _COMPONENT		ACPI_OS_SERVICES
> +ACPI_MODULE_NAME("osl");
> +
> +#define PREFIX			"ACPI: "
> +
> +/*
> + * The story of _OSI(Linux)
> + *
> + * From pre-history through Linux-2.6.22,
> + * Linux responded TRUE upon a BIOS OSI(Linux) query.
> + *
> + * Unfortunately, reference BIOS writers got wind of this
> + * and put OSI(Linux) in their example code, quickly exposing
> + * this string as ill-conceived and opening the door to
> + * an un-bounded number of BIOS incompatibilities.
> + *
> + * For example, OSI(Linux) was used on resume to re-POST a
> + * video card on one system, because Linux at that time
> + * could not do a speedy restore in its native driver.
> + * But then upon gaining quick native restore capability,
> + * Linux has no way to tell the BIOS to skip the time-consuming
> + * POST -- putting Linux at a permanent performance disadvantage.
> + * On another system, the BIOS writer used OSI(Linux)
> + * to infer native OS support for IPMI!  On other systems,
> + * OSI(Linux) simply got in the way of Linux claiming to
> + * be compatible with other operating systems, exposing
> + * BIOS issues such as skipped device initialization.
> + *
> + * So "Linux" turned out to be a really poor chose of
> + * OSI string, and from Linux-2.6.23 onward we respond FALSE.
> + *
> + * BIOS writers should NOT query _OSI(Linux) on future systems.
> + * Linux will complain on the console when it sees it, and return FALSE.
> + * To get Linux to return TRUE for your system  will require
> + * a kernel source update to add a DMI entry,
> + * or boot with "acpi_osi=Linux"
> + */
> +
> +static struct osi_linux {
> +	unsigned int	enable:1;
> +	unsigned int	dmi:1;
> +	unsigned int	cmdline:1;
> +	unsigned int	default_disabling:1;
> +} osi_linux = {0, 0, 0, 0};
> +
> +u32 acpi_osi_handler(acpi_string interface, u32 supported)
> +{
> +	if (!strcmp("Linux", interface)) {
> +
> +		printk_once(KERN_NOTICE FW_BUG PREFIX
> +			"BIOS _OSI(Linux) query %s%s\n",
> +			osi_linux.enable ? "honored" : "ignored",
> +			osi_linux.cmdline ? " via cmdline" :
> +			osi_linux.dmi ? " via DMI" : "");
> +	}
> +
> +	if (!strcmp("Darwin", interface)) {
> +		/*
> +		 * Apple firmware will behave poorly if it receives positive
> +		 * answers to "Darwin" and any other OS. Respond positively
> +		 * to Darwin and then disable all other vendor strings.
> +		 */
> +		acpi_update_interfaces(ACPI_DISABLE_ALL_VENDOR_STRINGS);
> +		supported = ACPI_UINT32_MAX;
> +	}
> +
> +	return supported;
> +}
> +
> diff --git a/drivers/acpi/osl.c b/drivers/acpi/osl.c
> index f9eeae8..c7f1cd6 100644
> --- a/drivers/acpi/osl.c
> +++ b/drivers/acpi/osl.c
> @@ -141,30 +141,6 @@ static struct osi_linux {
>  	unsigned int	default_disabling:1;
>  } osi_linux = {0, 0, 0, 0};
>  
> -static u32 acpi_osi_handler(acpi_string interface, u32 supported)
> -{
> -	if (!strcmp("Linux", interface)) {
> -
> -		printk_once(KERN_NOTICE FW_BUG PREFIX
> -			"BIOS _OSI(Linux) query %s%s\n",
> -			osi_linux.enable ? "honored" : "ignored",
> -			osi_linux.cmdline ? " via cmdline" :
> -			osi_linux.dmi ? " via DMI" : "");
> -	}
> -
> -	if (!strcmp("Darwin", interface)) {
> -		/*
> -		 * Apple firmware will behave poorly if it receives positive
> -		 * answers to "Darwin" and any other OS. Respond positively
> -		 * to Darwin and then disable all other vendor strings.
> -		 */
> -		acpi_update_interfaces(ACPI_DISABLE_ALL_VENDOR_STRINGS);
> -		supported = ACPI_UINT32_MAX;
> -	}
> -
> -	return supported;
> -}
> -
>  static void __init acpi_request_region (struct acpi_generic_address *gas,
>  	unsigned int length, char *desc)
>  {
> diff --git a/include/linux/acpi.h b/include/linux/acpi.h
> index 87f365e..ec18ab0 100644
> --- a/include/linux/acpi.h
> +++ b/include/linux/acpi.h
> @@ -271,6 +271,7 @@ static inline int acpi_video_display_switch_support(void)
>  extern int acpi_blacklisted(void);
>  extern void acpi_dmi_osi_linux(int enable, const struct dmi_system_id *d);
>  extern void acpi_osi_setup(char *str);
> +extern u32 acpi_osi_handler(acpi_string interface, u32 supported);
>  
>  #ifdef CONFIG_ACPI_NUMA
>  int acpi_get_node(acpi_handle handle);
> 

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