From: Andrew Morton <akpm-de/tnXTf+JLsfHDXvbKv3WD2FQJk+8+b@public.gmane.org>
Subject: Re: [patch 2.6.31-rc7] spi: Freescale STMP
	driver
Date: Wed, 2 Sep 2009 09:42:39 -0700
Message-ID: <20090902094239.d9d91680.akpm@linux-foundation.org>
References: <200908271847.43226.david-b@pacbell.net>
	<20090901135112.58f50b30.akpm@linux-foundation.org>
	<200909020847.18907.david-b@pacbell.net>
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Cc: spi-devel-general-5NWGOfrQmneRv+LV9MX5uipxlwaOVQ5f@public.gmane.org, dpervushin-L1vi/lXTdtvkgf6YlCu6wwC/G2K4zDHf@public.gmane.org
To: David Brownell <david-b-yBeKhBN/0LDR7s880joybQ@public.gmane.org>
In-Reply-To: <200909020847.18907.david-b-yBeKhBN/0LDR7s880joybQ@public.gmane.org>
Errors-To: spi-devel-general-bounces-5NWGOfrQmneRv+LV9MX5uipxlwaOVQ5f@public.gmane.org

On Wed, 2 Sep 2009 08:47:18 -0700 David Brownell <david-b-yBeKhBN/0LDR7s880joybQ@public.gmane.org> wrote:

> On Tuesday 01 September 2009, Andrew Morton wrote:
> > > +#define busy_wait(cond)____________________________________________________________________________________________________________\
> > > +__________({____________________________________________________________________________________________________________________________\
> > > +__________unsigned long end_jiffies = jiffies + STMP_SPI_TIMEOUT;__________________\
> > > +__________bool succeeded = false;__________________________________________________________________________________\
> > > +__________do {________________________________________________________________________________________________________________________\
> > > +__________________________if (cond) {__________________________________________________________________________________________\
> > > +__________________________________________succeeded = true;______________________________________________________________\
> > > +__________________________________________break;____________________________________________________________________________________\
> > > +__________________________}______________________________________________________________________________________________________________\
> > > +__________________________cpu_relax();________________________________________________________________________________________\
> > > +__________} while (time_before(end_jiffies, jiffies));________________________________________\
> > > +__________succeeded;____________________________________________________________________________________________________________\
> > > +__________})

(^^ your email client turns 0x09's into 0xa0's)


> > Oh dear.
> 
> Bothered me a bit too, but ... compared to <linux/wait.h> and
> all the wait_event_*() macros, I couldn't object much.  :)

The use of a macro is a minor issue.

The "oh dear" issue is that this driver does so much busy-waiting.

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