linux-kernel - Re: [patch 2.6.20-rc2] gpio_direction

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Date:	Fri, 2 Mar 2007 10:45:21 -0800
From:	David Brownell <david-b@...bell.net>
To:	Andrew Victor <andrew@...people.com>
Cc:	Linux Kernel list <linux-kernel@...r.kernel.org>,
	Milan Svoboda <msvoboda@...rockwell.com>,
	Haavard Skinnemoen <hskinnemoen@...el.com>
Subject: Re: [patch 2.6.20-rc2] gpio_direction_output() needs an initial value

On Thursday 01 March 2007 9:48 pm, Andrew Victor wrote:
> hi David,
> 
> > It's been pointed out that output GPIOs should have an initial value, to
> > avoid signal glitching ... among other things, it can be some time before
> > a driver is ready.  This patch corrects that oversight, fixing
> 
> For the AT91 changes:
>   Acked-by: Andrew Victor <andrew@...people.com>
> 
> 
> > --- g26.orig/drivers/spi/atmel_spi.c	2007-02-28 12:47:43.000000000 -0800
> > +++ g26/drivers/spi/atmel_spi.c	2007-03-01 15:29:30.000000000 -0800
> 
> > -		gpio_direction_output(npcs_pin);
> > +		gpio_direction_output(npcs_pin, !(spi->mode & SPI_CS_HIGH));
> >  	}
> 
> As mentioned previously (by Walter Tuppa), wouldn't it be better to just
> change this to:
>      cs_deactivate(spi);

That *does* deactivate the chipselect, as the initial value.
Given this function signature change, some initial value must
be specified, and that expression uses the inactive value...
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