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

[Julien Grall]

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.

Regards,

--
Julien Grall
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