linux-kernel - Re: [PATCH] [9/11] x86: Replace NSC/Cyrix specific chipset access macros by inlined functions.

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Date:	Sat, 21 Jul 2007 16:00:01 +0400
From:	Alexey Dobriyan <adobriyan@...il.com>
To:	Andi Kleen <ak@...e.de>
Cc:	juergen@...uzholzen.de, patches@...-64.org,
	linux-kernel@...r.kernel.org
Subject: Re: [PATCH] [9/11] x86: Replace NSC/Cyrix specific chipset access macros by inlined functions.

On Fri, Jul 20, 2007 at 05:32:53PM +0200, Andi Kleen wrote:
> --- /dev/null
> +++ linux/include/asm-i386/processor-cyrix.h
> @@ -0,0 +1,30 @@
> +/*
> + * NSC/Cyrix CPU indexed register access. Must be inlined instead of
> + * macros to ensure correct access ordering
> + * Access order is always 0x22 (=offset), 0x23 (=value)
> + *
> + * When using the old macros a line like
> + *   setCx86(CX86_CCR2, getCx86(CX86_CCR2) | 0x88);
> + * gets expanded to:
> + *  do {
> + *    outb((CX86_CCR2), 0x22);
> + *    outb((({
> + *        outb((CX86_CCR2), 0x22);
> + *        inb(0x23);
> + *    }) | 0x88), 0x23);
> + *  } while (0);
> + *
> + * which in fact violates the access order (= 0x22, 0x22, 0x23, 0x23).
> + */
> +
> +static inline u8 getCx86(u8 reg)
> +{
> +	outb(reg, 0x22);
> +	return inb(0x23);
> +}
> +
> +static inline void setCx86(u8 reg, u8 data)
> +{
> +	outb(reg, 0x22);
> +	outb(data, 0x23);
> +}

Why bother with new header, just make static inline in asm/processor.h.

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