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Date: Wed, 24 Aug 2005 19:31:31 +0200 (CEST)
From: moreau francis <francis_moreau2000@yahoo.fr>
Subject: Re: question on memory barrier
To: "linux-os \(Dick Johnson\)" <linux-os@analogic.com>
Cc: linux-kernel@vger.kernel.org
In-Reply-To: <Pine.LNX.4.61.0508240854550.28064@chaos.analogic.com>
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--- "linux-os (Dick Johnson)" <linux-os@analogic.com> a écrit :

> 
> On Wed, 24 Aug 2005, moreau francis wrote:
> 
> > Hi,
> >
> > I'm currently trying to write a USB driver for Linux. The device must be
> > configured by writing some values into the same register but I want to be
> > sure that the writing order is respected by either the compiler and the
> cpu.
> >
> > For example, here is a bit of driver's code:
> >
> > """
> > #include <asm/io.h>
> >
> > static inline void dev_out(u32 *reg, u32 value)
> > {
> >        writel(value, regs);
> > }
> >
> > void config_dev(void)
> > {
> >        dev_out(reg_a, 0x0); /* first io */
> >        dev_out(reg_a, 0xA); /* second io */
> > }
> >
> 
> This should be fine. The effect of the first bit of code
> plus all side-effects (if any) should be complete at the
> first effective sequence-point (;) but you need to

sorry but I'm not sure to understand you...Do you mean that the first write
into reg_a pointer will be completed before the second write because they're
separated by a (;) ?
Or because writes are encapsulated inside an inline function, therefore
compiler
must execute every single writes before returning from the inline function ?

Thanks.

            Francis


	

	
		
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