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

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

[Baruch Siach]

Hi Javier,

On Tue, May 19, 2015 at 03:34:11PM +0200, Javier Martinez Canillas wrote:
> Google Chromebooks have a SPI flash that is used to store firmware and
> different system parameters and data (i.e: Google Binary Block flags).
> 
> Since there isn't a driver for it yet, the spidev interface is used to
> access the flash from user-space (i.e: using the flashrom tool).
> 
> Add a "google,spi-flash" compatible string so the Device Tree sources
> use it instead of the "spidev" compatible which does not describe the
> real HW and is just a Linux implementation detail.
> 
> A generic "google,spi-flash" OF device ID is used instead of the actual
> vendor/model because these chips are commodity parts that are sourced
> from multiple vendors. So specifying the exact vendor and model in the
> DTS will add a maintenance burden with no real gain (the parts are 100%
> compatible anyways) and will likely result in it simply being wrong for
> a sizeable fraction of the machines.

The compatible string and dt binding should be documented somewhere under 
Documentation/devicetree/bindings/. Also, please keep the dt list on Cc for dt 
related patches.

baruch

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

[Javier Martinez Canillas]

Hello Baruch,

On 05/19/2015 09:53 PM, Baruch Siach wrote:
> Hi Javier,
> 
> On Tue, May 19, 2015 at 03:34:11PM +0200, Javier Martinez Canillas wrote:
>> Google Chromebooks have a SPI flash that is used to store firmware and
>> different system parameters and data (i.e: Google Binary Block flags).
>> 
>> Since there isn't a driver for it yet, the spidev interface is used to
>> access the flash from user-space (i.e: using the flashrom tool).
>> 
>> Add a "google,spi-flash" compatible string so the Device Tree sources
>> use it instead of the "spidev" compatible which does not describe the
>> real HW and is just a Linux implementation detail.
>> 
>> A generic "google,spi-flash" OF device ID is used instead of the actual
>> vendor/model because these chips are commodity parts that are sourced
>> from multiple vendors. So specifying the exact vendor and model in the
>> DTS will add a maintenance burden with no real gain (the parts are 100%
>> compatible anyways) and will likely result in it simply being wrong for
>> a sizeable fraction of the machines.
> 
> The compatible string and dt binding should be documented somewhere under 
> Documentation/devicetree/bindings/. Also, please keep the dt list on Cc for dt 
> related patches.
>

Yes, I didn't add a binding doc because this is mostly a RFC to see if
Mark finds the approach feasible but yes I should had included anyways,
sorry about that.

I'll add when posting as a proper patch if he agrees with the solution.
 
> baruch
> 

Best regards,
Javier