linux-kernel - RE: [PATCH] ACPI: allow compilation with bare metal compilers

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Date:   Tue, 15 Nov 2016 15:43:46 +0000
From:   "Moore, Robert" <robert.moore@...el.com>
To:     Al Stone <ahs3@...hat.com>,
        "linux-acpi@...r.kernel.org" <linux-acpi@...r.kernel.org>,
        "devel@...ica.org" <devel@...ica.org>,
        "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>
CC:     "Rafael J . Wysocki" <rjw@...ysocki.net>,
        Len Brown <lenb@...nel.org>, "Zheng, Lv" <lv.zheng@...el.com>
Subject: RE: [PATCH] ACPI: allow compilation with bare metal compilers

The design for all of this is as follows:

1) OS-dependent includes
2) Compiler-specific includes
3) acenv.h is the master file that pulls in the correct headers (one compiler, and one OS)

So, I think I see a couple of possible solutions for you:

1) If you are using GCC, the __GNUC__ symbol should already be defined.

2) If "aclinux.h" works for you, we can either add a conditional case that would apply to your environment, or:
2a) You could define _LINUX in your gcc invocations.

Because ACPICA supports many different environments, we don't want to have a "default" case which in a sense would only be an attempt to guess what the user intended. We want to have a clear error that tells the user that something important needs to be done before the code can be compiled.

Bob


> -----Original Message-----
> From: Al Stone [mailto:ahs3@...hat.com]
> Sent: Monday, November 14, 2016 3:09 PM
> To: linux-acpi@...r.kernel.org; devel@...ica.org; linux-
> kernel@...r.kernel.org
> Cc: Al Stone <ahs3@...hat.com>; Rafael J . Wysocki <rjw@...ysocki.net>;
> Len Brown <lenb@...nel.org>; Moore, Robert <robert.moore@...el.com>;
> Zheng, Lv <lv.zheng@...el.com>
> Subject: [PATCH] ACPI: allow compilation with bare metal compilers
> 
> The ACPICA subsystem of the ACPI driver sets up a compilation
> environment for itself, adding in multiple typedefs unique to ACPICA
> that depend on where ACPICA will be used.
> 
> The vast majority of such environments (Linux, QNX, ...) have an
> environment defined by the acenv.h header file.  When using a Linaro
> compiler [1] specifically built to be used in an embedded environment
> with perhaps a kernel and an init process as the only things running,
> there is no environment defined for ACPICA so the typedefs it needs are
> not set up, causing compilation to fail badly unless ACPI is completely
> disabled.
> Since ACPI is enabled in the default config for the kernel, the
> compilation failure is fairly obvious.
> 
> This may not be the optimal solution, but add in to the ACPI header file
> include/acpi/platform/acenv.h a default so that if GCC is being used,
> and all else fails, assume that we are going to be in a Linux-like
> environment and re-use the environment definition for Linux.  This
> allows us to build a kernel using this compiler [1] with or without
> ACPI.
> 
> [1]
> https://releases.linaro.org/components/toolchain/binaries/latest/aarch64
> -elff/gcc-linaro-6.1.1-2016-08-x86_64_aarch64-elf.tar.xz
> 
> Signed-off-by: Al Stone <ahs3@...hat.com>
> Cc: Rafael J. Wysocki <rjw@...ysocki.net>
> Cc: Len Brown <lenb@...nel.org>
> Cc: Robert Moore <robert.moore@...el.com>
> Cc: Lv Zheng <lv.zheng@...el.com>
> ---
>  include/acpi/platform/acenv.h | 15 +++++++++++++++
>  1 file changed, 15 insertions(+)
> 
> diff --git a/include/acpi/platform/acenv.h
> b/include/acpi/platform/acenv.h index 34cce72..cdd1cd6 100644
> --- a/include/acpi/platform/acenv.h
> +++ b/include/acpi/platform/acenv.h
> @@ -234,6 +234,21 @@
>  #elif defined(_AED_EFI) || defined(_GNU_EFI) || defined(_EDK2_EFI)
> #include "acefi.h"
> 
> +/*
> + * Up to this point, we've been looking for specific environments.  In
> + * some cases, there is no environment, and we're just working on bare
> + * metal.  However, since we're compiling the Linux kernel, let's just
> + * pretend we're in a Linux environment.
> + */
> +#elif defined(__GNUC__) && !defined(__INTEL_COMPILER) #if
> +!defined(_LINUX) #define _LINUX #endif #if !defined(__linux__) #define
> +__linux__ #endif #include <acpi/platform/aclinux.h>
> +
>  #else
> 
>  /* Unknown environment */
> --
> 2.10.2