linux-kernel - Re: [PATCH v5 01/14] x86/boot: enumerate documentation for the x86 hardware

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Message-ID: <20160413080132.GA9697@gmail.com>
Date:	Wed, 13 Apr 2016 10:01:32 +0200
From:	Ingo Molnar <mingo@...nel.org>
To:	"Luis R. Rodriguez" <mcgrof@...nel.org>
Cc:	bp@...en8.de, hpa@...or.com, tglx@...utronix.de, mingo@...hat.com,
	rusty@...tcorp.com.au, x86@...nel.org,
	linux-kernel@...r.kernel.org, luto@...capital.net,
	boris.ostrovsky@...cle.com, david.vrabel@...rix.com,
	konrad.wilk@...cle.com, xen-devel@...ts.xensource.com,
	lguest@...ts.ozlabs.org, andriy.shevchenko@...ux.intel.com,
	jlee@...e.com, glin@...e.com, matt@...eblueprint.co.uk,
	andrew.cooper3@...rix.com, rjw@...ysocki.net, lenb@...nel.org,
	robert.moore@...el.com, lv.zheng@...el.com, toshi.kani@...com,
	linux-acpi@...r.kernel.org, kozerkov@...allels.com,
	josh@...htriplett.org, joro@...tes.org, tiwai@...e.de
Subject: Re: [PATCH v5 01/14] x86/boot: enumerate documentation for the x86
 hardware_subarch


* Luis R. Rodriguez <mcgrof@...nel.org> wrote:

> Although hardware_subarch has been in place since the x86 boot
> protocol 2.07 it hasn't been used much. Enumerate current possible
> values to avoid misuses and help with semantics later at boot
> time should this be used further.
> 
> These enums should only ever be used by architecture x86 code,
> and all that code should be well contained and compartamentalized,
> clarify that as well.
> 
> v2: updates documentation further -- be a bit more pedantic about
>     annotating care and use of these guys.
> v3: Use s/SOC/SoC and also anntoate that both domU and dom0 are
>     both currently supported through the PV boot path.
> 
> Cc: Andy Shevchenko <andriy.shevchenko@...ux.intel.com>
> Signed-off-by: Luis R. Rodriguez <mcgrof@...nel.org>
> ---
>  arch/x86/include/uapi/asm/bootparam.h | 37 ++++++++++++++++++++++++++++++++++-
>  1 file changed, 36 insertions(+), 1 deletion(-)
> 
> diff --git a/arch/x86/include/uapi/asm/bootparam.h b/arch/x86/include/uapi/asm/bootparam.h
> index 329254373479..bf9fea2f4591 100644
> --- a/arch/x86/include/uapi/asm/bootparam.h
> +++ b/arch/x86/include/uapi/asm/bootparam.h
> @@ -157,7 +157,42 @@ struct boot_params {
>  	__u8  _pad9[276];				/* 0xeec */
>  } __attribute__((packed));
>  
> -enum {
> +/**
> + * enum x86_hardware_subarch - x86 hardware subarchitecture

Could you add some prominent warning here, like:

> + * WARNING: the 'x86 subarch flag' is only used for legacy hacks, for platform
> + *          features that are not easily enumerated or discoverable. You should
> + *          not ever use this for new features.

Thanks,

	Ingo