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

[Stefano Stabellini]

On Mon, 23 Mar 2015, Hanjun Guo wrote:
> 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.

Me too
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