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

[Hanjun Guo]

On 2015/3/23 6:11, Rafael J. Wysocki wrote:
> On Sunday, March 22, 2015 09:32:48 PM Julien Grall wrote:
>> 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@xxxxxxxxxx <mailto:hanjun.guo@xxxxxxxxxx>>
>>>>>      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@xxxxxxxxxx
>>>>>      <mailto:hanjun.guo@xxxxxxxxxx>>
>>>>>      ---
>>>>>        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.
> Oh well, not really.  You're moving a config-time check to compile time
> which means that it will be done every time this Makefile is executed
> and for all architectures that execute it.  Not nice.
>
> Also I think that ia64 is missing from the list, but I may be wrong.

In commit d52eefb47d (ia64/xen: Remove Xen support for ia64), XEN is
not supported anymore on ia64 now.

>
> Not to mention the fact that the dependency will be rather difficult to find
> for tools like xconfig ...

I also think introducing a CONFIG_ option is a better idea.

Thanks
Hanjun

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