Hi, 

> From: Hanjun Guo [mailto:hanjun.guo@linaro.org]
> Sent: Thursday, June 05, 2014 12:11 PM
> To: Zheng, Lv; Lee Jones; Rafael J. Wysocki
> 
> On 2014-6-5 9:14, Zheng, Lv wrote:
> > Hi, Lee
> >
> >> From: Lee Jones [mailto:lee.jones@linaro.org]
> >> Sent: Wednesday, June 04, 2014 8:52 PM
> >> To: Rafael J. Wysocki
> >>
> >> On Wed, 04 Jun 2014, Rafael J. Wysocki wrote:
> >>
> >>> On Wednesday, June 04, 2014 01:09:50 PM Lee Jones wrote:
> >>>> Any drivers which support ACPI and Device Tree probing need to include
> >>>> both respective header files.  Without this patch, if a driver is being
> >>>> used on a platform which does not support ACPI and subsequently does not
> >>>> have the config option enabled, but includes linux/acpi.h the build
> >>>> breaks with:
> >>>>
> >>>>   In file included from ../include/acpi/platform/acenv.h:150:0,
> >>>>                    from ../include/acpi/acpi.h:56,
> >>>>                    from ../include/linux/match.h:2,
> >>>>                    from ../drivers/i2c/i2c-core.c:43:
> >>>>   ../include/acpi/platform/aclinux.h:73:23:
> >>>>    fatal error: asm/acenv.h: No such file or directory
> >>>>    #include <asm/acenv.h>
> >>>>                        ^
> >
> > Note that:
> > In our tree:
> > <asm/acenv.h> is only included by <acpi/acpi.h>.
> > And <acpi/acpi.h> is only included by
> > 1. <linux/acpi.h> when CONFIG_ACPI enabled
> > 2. <linux/sfi_acpi.h> - this is x86 specific, we'll clean it up by implementing stubs for all ACPI external interfaces.
> > So there is no case we need to exclude <asm/acenv.h> when CONFIG_ACPI is not enabled.
> >
> > I cannot find linux/match.h here.
> > If <linux/match.h> want to include ACPI features, it shouldn't include <acpi/acpi.h>, but should include <linux/acpi.h>.
> > Please refer to:
> > https://git.kernel.org/cgit/linux/kernel/git/torvalds/linux.git/commit/?id=8b48463f
> > And stop including <acpi/acpi.h> directly in any cases.
> 
> Ah, I agree, please ignore my previous email,
> sorry for the noise.
> 
> Since it is very important to include <linux/acpi.h> but not <acpi/acpi.h>,
> can we document it somewhere as the guidance? Then people will not
> make such mistake :)

After I test the ACPICA stubs and remove the only abnormal direct <acpi/acpi.h> inclusion from <linux/sfi_acpi.h>.
We could have a commit to add something like:

#ifndef _LINUX_ACPI_H
#error ....
#endif
To the <acpi/platform/aclinux.h> (the Linux OSL for ACPICA headers, it is included by <acpi/acpi.h>).
Hope this can be the hint to prevent future mistakes.

Thanks and best regards
-Lv


> 
> Thanks
> Hanjun