linux-kernel - Re: [PATCH] spi: spi-gpio: Add check for cs-gpios dt property

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Date:	Wed, 13 Nov 2013 15:33:00 +0100
From:	Gerlando Falauto <gerlando.falauto@...mile.com>
To:	Mark Brown <broonie@...nel.org>
CC:	"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
	Maxime Ripard <maxime.ripard@...e-electrons.com>
Subject: Re: [PATCH] spi: spi-gpio: Add check for cs-gpios dt property

Hi Mark,

On 11/13/2013 02:33 PM, Mark Brown wrote:
> On Wed, Nov 13, 2013 at 09:02:28AM +0100, Gerlando Falauto wrote:
>> The bindings assumed that the cs-gpios property is always there.
>> However, a single SPI device can also work fine without an explicit chip select.
>> Use the SPI_GPIO_NO_CHIPSELECT mode when the property is not present or invaild.
>
> Given that for most systems a missing /CS would be an error it seems
> better to add an explicit property to enable this in order to help make
> problems with the more common case more obvious.
>

Thank you for your answer.
How about an empty

	cs-gpios;

property? To explicitly state we haven't just forgotten it -- we just 
know we don't have one instead. (There are plenty of empty "ranges;" 
properties in ARM DTSes -- I don't know if the use case is the same though).

Or else a null-valued

	cs-gpios = <0>;

property?

I'm open to other proposals of course.

Thanks again!
Gerlando
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