linux-kernel - Re: [PATCH v10 00/21] Introduce ACPI for ARM64 based on ACPI 5.1

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Message-ID: <550F3500.1040608@linaro.org>
Date:	Sun, 22 Mar 2015 21:32:48 +0000
From:	Julien Grall <julien.grall@...aro.org>
To:	"Rafael J. Wysocki" <rjw@...ysocki.net>
CC:	Naresh Bhat <naresh.bhat@...aro.org>,
	Hanjun Guo <guohanjun@...wei.com>,
	Hanjun Guo <hanjun.guo@...aro.org>,
	Jon Fraser <jfraser@...adcom.com>,
	Parth Dixit <parth.dixit@...aro.org>,
	Stefano Stabellini <stefano.stabellini@...citrix.com>,
	Catalin Marinas <Catalin.Marinas@....com>,
	Olof Johansson <olof@...om.net>,
	"grant.likely@...aro.org" <grant.likely@...aro.org>,
	Lorenzo Pieralisi <Lorenzo.Pieralisi@....com>,
	Arnd Bergmann <arnd@...db.de>,
	Mark Rutland <Mark.Rutland@....com>,
	"graeme.gregory@...aro.org" <graeme.gregory@...aro.org>,
	Sudeep Holla <Sudeep.Holla@....com>,
	"jcm@...hat.com" <jcm@...hat.com>,
	Marc Zyngier <Marc.Zyngier@....com>,
	Mark Brown <broonie@...nel.org>,
	Robert Richter <rric@...nel.org>,
	Timur Tabi <timur@...eaurora.org>,
	Ashwin Chaugule <ashwinc@...eaurora.org>,
	"suravee.suthikulpanit@....com" <suravee.suthikulpanit@....com>,
	"linux-acpi@...r.kernel.org" <linux-acpi@...r.kernel.org>,
	"linux-arm-kernel@...ts.infradead.org" 
	<linux-arm-kernel@...ts.infradead.org>,
	"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
	"linaro-acpi@...ts.linaro.org" <linaro-acpi@...ts.linaro.org>,
	Ian Campbell <Ian.Campbell@...rix.com>
Subject: Re: [PATCH v10 00/21] Introduce ACPI for ARM64 based on ACPI 5.1



On 22/03/2015 21:49, Rafael J. Wysocki wrote:
> On Sunday, March 22, 2015 09:05:21 PM Julien Grall wrote:
>> Hello,
>>
>> On 21/03/2015 12:09, Naresh Bhat wrote:
>>>       From 268dcdafa34a690e2f99c0784ca33a6d2352ecf5 Mon Sep 17 00:00:00 2001
>>>      From: Hanjun Guo <hanjun.guo@...aro.org <mailto:hanjun.guo@...aro.org>>
>>>      Date: Sat, 21 Mar 2015 14:43:54 +0800
>>>      Subject: [PATCH] XEN / ACPI: Make XEN ACPI depend on X86
>>>
>>>      When ACPI is enabled on ARM64, XEN ACPI will also compiled
>>>      into the kernel, but XEN ACPI is x86 dependent, so introduce
>>>      CONFIG_XEN_ACPI to make it depend on x86 before XEN ACPI is
>>>      functional on ARM64.
>>>
>>>      Signed-off-by: Hanjun Guo <hanjun.guo@...aro.org
>>>      <mailto:hanjun.guo@...aro.org>>
>>>      ---
>>>        drivers/xen/Kconfig  | 4 ++++
>>>        drivers/xen/Makefile | 2 +-
>>>        2 files changed, 5 insertions(+), 1 deletion(-)
>>>
>>>      diff --git a/drivers/xen/Kconfig b/drivers/xen/Kconfig
>>>      index b812462..a31cd29 100644
>>>      --- a/drivers/xen/Kconfig
>>>      +++ b/drivers/xen/Kconfig
>>>      @@ -253,4 +253,8 @@ config XEN_EFI
>>>            def_bool y
>>>            depends on X86_64 && EFI
>>>
>>>      +config XEN_ACPI
>>>      +    def_bool y
>>>      +    depends on X86 && ACPI
>>>      +
>>>        endmenu
>>>      diff --git a/drivers/xen/Makefile b/drivers/xen/Makefile
>>>      index 2ccd359..f4622ab 100644
>>>      --- a/drivers/xen/Makefile
>>>      +++ b/drivers/xen/Makefile
>>>      @@ -13,7 +13,7 @@ CFLAGS_efi.o                += -fshort-wchar
>>>
>>>        dom0-$(CONFIG_PCI) += pci.o
>>>        dom0-$(CONFIG_USB_SUPPORT) += dbgp.o
>>>      -dom0-$(CONFIG_ACPI) += acpi.o $(xen-pad-y)
>>>      +dom0-$(CONFIG_XEN_ACPI) += acpi.o $(xen-pad-y)
>>>        xen-pad-$(CONFIG_X86) += xen-acpi-pad.o
>>>        dom0-$(CONFIG_X86) += pcpu.o
>>>        obj-$(CONFIG_XEN_DOM0)            += $(dom0-y)
>>
>> [..]
>>
>>>
>>> AFAIK,  There is already a kernel patch exists to fix this issue.  I
>>> think  Julien or Parth is a right person to ask.  Hence I am CCed Julien
>>> Grall too.
>>
>> The ACPI support for Xen is not ready. So I think avoiding to compile
>> drivers/xen/acpi.c on ARM64/ARM seems the better solution for now.
>>
>> Although, rather than introducing a new CONFIG option, I would use the
>> same trick we use within the Makefile to avoid hotplug.c on ARM/ARM64.
>>
>> ifeq ($(filter y, $(CONFIG_ARM) $(CONFIG_ARM64)), )
>> dom0-$(CONFIG_ACPI) += acpi.o $(xen-pad-y)
>> endif
>
> Well, is avoiding an extra CONFIG_ option worth the ugliness of this?

When the support of ACPI for Xen will come, the CONFIG_ option will be 
an alias to CONFIG_XEN.

In this case the CONFIG_ option won't bring much improvement to the code 
and add an extra indirection.

The "ugliness" option has, at least, the advantage to be tiny and 
self-contained.

Regards,

-- 
Julien Grall
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