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use of volatile in iounmap()?

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From: Sam Ravnborg <sam@...>
To: LKML <linux-kernel@...>
Cc: Ingo Molnar <mingo@...>
Subject: use of volatile in iounmap()?
Date: Friday, March 28, 2008 - 4:34 pm

While reviewing some CAN driver I stumbled on iounmap
which has following prototype on x86:

extern void iounmap(volatile void __iomem *addr);

I argued that the driver should not use volatile
but then I cannot explain why the argument to
iounmap takes a volatile.

The same goes for many other functions in
the io*.h headers.

Grepping the other archs they mostly follow
same pattern.

Can anyone explain the rational for volatile in this case.

Thanks,
	Sam
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Messages in current thread:
use of volatile in iounmap()?, Sam Ravnborg, (Fri Mar 28, 4:34 pm)
Re: use of volatile in iounmap()?, Al Viro, (Fri Mar 28, 5:17 pm)
Re: use of volatile in iounmap()?, H. Peter Anvin, (Fri Mar 28, 4:51 pm)
Re: use of volatile in iounmap()?, Sam Ravnborg, (Fri Mar 28, 5:04 pm)
Re: use of volatile in iounmap()?, H. Peter Anvin, (Fri Mar 28, 5:07 pm)