linux-kernel - RE: [PATCH] [drivers] [SPI] SPI_GPIO: add support for controllers with missing MISO pin

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Message-id: <000901c9d79a$f36a86b0$da3f9410$%szyprowski@samsung.com>
Date:	Mon, 18 May 2009 11:27:59 +0200
From:	Marek Szyprowski <m.szyprowski@...sung.com>
To:	'Daniel Mack' <daniel@...aq.de>, 'Ben Dooks' <ben-linux@...ff.org>
Cc:	'LKML' <linux-kernel@...r.kernel.org>,
	linux-arm-kernel@...ts.arm.linux.org.uk, kyungmin.park@...sung.com
Subject: RE: [PATCH] [drivers] [SPI] SPI_GPIO: add support for controllers with
 missing MISO pin

Hello,

On Monday, May 18, 2009 10:57 AM Daniel Mack wrote:

> On Mon, May 18, 2009 at 09:34:12AM +0100, Ben Dooks wrote:
> > > > >  static inline int getmiso(const struct spi_device *spi)
> > > > >  {
> > > > > -	return !!gpio_get_value(SPI_MISO_GPIO);
> > > > > +	if (SPI_MISO_GPIO)
> > > > > +		return !!gpio_get_value(SPI_MISO_GPIO);
> > > > > +	else
> > > > > +		return 0;
> > > > >  }
> > > >
> > > > Is zero a good approximation for 'no gpio' ?
> > >
> > > Now I found that zero might be a valid gpio pin number on some
> architectures
> > > (it just means GPIO0 pin). This is imho a bit strange behavior of
> gpiolib as
> > > there should be also a special values for INVALID or NOGPIO cases.
> Does
> > > anyone have any ideas how such cases should be handled properly?
> >
> > I belive there is a gpio_is_valid() function to tell you precisely if
> > the given GPIO is valid.
> 
> And then -1 can be passed in from the platform data which will fail the
> gpio_is_valid() test.

Ok. I will update my patch. Thank you for the idea.

Best regards
--
Marek Szyprowski
Samsung Poland R&D Center


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