linux-kernel - Re: [PATCH 1/1] edac x38: new MC driver module

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Date:	Sun, 23 Nov 2008 15:52:23 -0800
From:	"H. Peter Anvin" <hpa@...or.com>
To:	Hitoshi Mitake <h.mitake@...il.com>
CC:	Russell King <rmk+lkml@....linux.org.uk>,
	Ralf Baechle <ralf@...ux-mips.org>,
	Andrew Morton <akpm@...ux-foundation.org>,
	Doug Thompson <norsk5@...oo.com>, dougthompson@...ssion.com,
	linux-kernel@...r.kernel.org, linux-arch@...r.kernel.org
Subject: Re: [PATCH 1/1] edac x38: new MC driver module

Hitoshi Mitake wrote:
> --- a/arch/x86/include/asm/io.h
> +++ b/arch/x86/include/asm/io.h
> @@ -57,6 +57,14 @@ build_mmio_write(__writeq, "q", unsigned long, "r", )
>  /* Let people know we have them */
>  #define readq readq
>  #define writeq writeq
> +
> +#else  /* CONFIG_X86_32 */
> +
> +static inline unsigned long readq(const volatile void __iomem *addr)
> +{
> +	return readl(addr) | (((u64)readl(addr + 4)) << 32);
> +}
> +
>  #endif
>  

Let's see:

* undefined ordering of operations (at least on x86, they really should
be performed in LSB first order.)

* Using "unsigned long" for a 64-bit number on a 32-bit architecture.

* Arithmetic on a void pointer.


Try something like:

static inline u64 readq(const volative void __iomem *addr)
{
	volatile u32 __iomem *__p = addr;
	u32 __l, __h;

	__l = readl(p);
	__h = readl(p+1);

	return __l + ((u64)__h << 32);
}

	-hpa
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