Re: [PATCH v3 2/3] ACPI / ARM64: add BAD_MADT_GICC_ENTRY() macro

From	Catalin Marinas <catalin.marinas@arm.com>
Newsgroups	linux.kernel
Subject	Re: [PATCH v3 2/3] ACPI / ARM64: add BAD_MADT_GICC_ENTRY() macro
Date	2015-07-03 16:10 +0200
Message-ID	<pI9Pc-13T-7@gated-at.bofh.it> (permalink)
References	<pHWoV-X2-1@gated-at.bofh.it> <pHWoV-X2-7@gated-at.bofh.it>
Organization	linux.* mail to news gateway

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On Thu, Jul 02, 2015 at 05:48:35PM -0600, Al Stone wrote:
> diff --git a/arch/arm64/include/asm/acpi.h b/arch/arm64/include/asm/acpi.h
> index 39248d3..a3c26a4 100644
> --- a/arch/arm64/include/asm/acpi.h
> +++ b/arch/arm64/include/asm/acpi.h
> @@ -19,6 +19,17 @@
>  #include <asm/psci.h>
>  #include <asm/smp_plat.h>
>  
> +/* Macros for consistency checks of the GICC subtable of MADT */
> +#define ACPI_MADT_GICC_51_LENGTH       76
> +#define ACPI_MADT_GICC_60_LENGTH       80
> +
> +#define BAD_MADT_GICC_ENTRY(entry, end) (                                   \
> +		(!entry) || (unsigned long)entry + sizeof(*entry) > end ||  \
> +		((ACPI_FADT_SPEC_VERSION == ACPI_FADT_SPEC_VERSION_51) &&   \
> +		 (entry->header.length != ACPI_MADT_GICC_51_LENGTH))    ||  \
> +		((ACPI_FADT_SPEC_VERSION == ACPI_FADT_SPEC_VERSION_60) &&   \
> +		 (entry->header.length != ACPI_MADT_GICC_60_LENGTH)))

This looks ugly but, well, we could live with this.

However, I'd like to avoid having to extend this macro every time we get
a new spec released, like 6.1 defining another 80 or 84 etc. So, how
about we only update this when there is an actual change in the length?
Something like:

#define ACPI_MADT_GICC_LENGTH	({					\
	u8 length;							\
	if (ACPI_FADT_SPEC_VERSION < ACPI_FADT_SPEC_VERSION_6_0)	\
		length = 76;						\
	else								\
		length = 80;						\
	length;								\
})

or just:

#define ACPI_MADT_GICC_LENGTH	\
	(ACPI_FADT_SPEC_VERSION < ACPI_FADT_SPEC_VERSION_6_0 ? 76 : 80)

(the latter is simpler but may not look nice if we change it again in
6.1; though we could re-write this macro when needed, not a problem)

-- 
Catalin
--
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Thread

[PATCH v3 0/3] Correct for ACPI 5.1->6.0 spec changes in MADT GICC entries Al Stone <al.stone@linaro.org> - 2015-07-03 01:50 +0200
  [PATCH v3 3/3] ACPI / ARM64 : use the new BAD_MADT_GICC_ENTRY macro Al Stone <al.stone@linaro.org> - 2015-07-03 01:50 +0200
  [PATCH v3 2/3] ACPI / ARM64: add BAD_MADT_GICC_ENTRY() macro Al Stone <al.stone@linaro.org> - 2015-07-03 01:50 +0200
    Re: [PATCH v3 2/3] ACPI / ARM64: add BAD_MADT_GICC_ENTRY() macro Catalin Marinas <catalin.marinas@arm.com> - 2015-07-03 16:10 +0200
      Re: [PATCH v3 2/3] ACPI / ARM64: add BAD_MADT_GICC_ENTRY() macro Al Stone <ahs3@redhat.com> - 2015-07-06 23:30 +0200
  [PATCH v3 1/3] ACPI : introduce macros for using the ACPI specification version Al Stone <al.stone@linaro.org> - 2015-07-03 01:50 +0200
    Re: [PATCH v3 1/3] ACPI : introduce macros for using the ACPI specification version "Rafael J. Wysocki" <rjw@rjwysocki.net> - 2015-07-03 02:00 +0200
  Re: [PATCH v3 1/3] ACPI : introduce macros for using the ACPI specification  version Al Stone <ahs3@redhat.com> - 2015-07-07 00:00 +0200
    Re: [PATCH v3 1/3] ACPI : introduce macros for using the ACPI specification version "Rafael J. Wysocki" <rjw@rjwysocki.net> - 2015-07-07 00:20 +0200

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