linux-kernel - Re: [RFC PATCH 1/4] spi: spidev: Add Google SPI flash compatible string

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Date:	Wed, 20 May 2015 13:21:53 +0200
From:	Javier Martinez Canillas <javier.martinez@...labora.co.uk>
To:	Mark Brown <broonie@...nel.org>
CC:	Kukjin Kim <kgene@...nel.org>,
	Krzysztof Kozlowski <k.kozlowski@...sung.com>,
	Olof Johansson <olof@...om.net>,
	Doug Anderson <dianders@...omium.org>,
	David Hendricks <dhendrix@...gle.com>,
	linux-samsung-soc@...r.kernel.org,
	linux-arm-kernel@...ts.infradead.org, linux-kernel@...r.kernel.org
Subject: Re: [RFC PATCH 1/4] spi: spidev: Add Google SPI flash compatible
 string

Hello Mark,

On 05/20/2015 12:37 PM, Mark Brown wrote:
> On Wed, May 20, 2015 at 12:18:13PM +0200, Javier Martinez Canillas wrote:
>> On 05/20/2015 12:13 PM, Mark Brown wrote:
> 
>> > This is adding a binding with no documentation, documentation is
>> > mandatory for all bindings.
> 
>> Yes, I missed... sorry about that. Do you agree with the approach
>> though so I can re-spin the patches adding the missing DT binding?
> 
> It's probably OK but I didn't really drill through since the binding was
> missing.  If these parts are commodity as described it seems surprising
> that they aren't compatible with any existing kernel driver.
> 

The ChromeOS user-space just uses flashrom to send a raw stream of bytes
via spidev to the SPI NOR flash chip. There is drivers/mtd/spi-nor/spi-nor.c
but AFAIU there are some limitations when interfacing the flash through
the MTD layer, for example there isn't a way to set the SPI flash write
protection through MTD. But I'll do some investigation before re-spinning
the patches.

BTW, the other "rohm,dh2228fv" compatible string in spidev added by commit
8fad805bdc52 ("spi: spidev: Add Rohm DH2228FV DAC compatible string"), also
does not have a documented DT binding so that should be fixed as well.

Best regards,
Javier
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