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From: David Brownell <david-b@pacbell.net>
To: Nick Piggin <nickpiggin@yahoo.com.au>
Subject: Re: [patch 2.6.24-rc2 1/3] generic gpio -- gpio_chip support
Date: Wed, 14 Nov 2007 22:23:45 -0800
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Cc: Andrew Morton <akpm@linux-foundation.org>, Ingo Molnar <mingo@elte.hu>,
       Linux Kernel list <linux-kernel@vger.kernel.org>,
       Florian Fainelli <florian.fainelli@telecomint.eu>,
       Haavard Skinnemoen <hskinnemoen@atmel.com>
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On Tuesday 13 November 2007, Nick Piggin wrote:
> > > But these ones
> > > are raw locks rather than normal locks probably because that
> > > they are trivially an innermost and correct lock.
> >
> > As in the $SUBJECT case, I'd say.
> >
> > Although another point is related to "trivial":  the data
> > is being protected through an operation too trivial to be
> > worth paying for any of that priority logic.
> 
> A driver shouldn't get to decide that, IMO.

Not that I was talking about driver code...


> And if there is 
> some policy in the -rt tree allowing these decisions, then
> it's exactly the kind of thing we don't want upsream.

Making raw spinlocks available allows those decisions...

On the other hand, I can't see things working sanely
without them being available.  The problem seems to be
the usual one that crops up whenever anyone tries to
create a "bright line" decision algorithm in areas that
need flexibility.  Any "bright line" rule will lead to
wrong results.

- Dave