Re: [PATCH] ARM: Kirkwood: Add DT description of QNAP 419

[Arnd Bergmann <arnd@arndb.de>]

On Saturday 11 January 2014, Andrew Lunn wrote:
> The id of -1 causes platform_device_add() to set the device name to
> plain "gpio-keys".
> 
> When using DT, the device name is created by the function
> of_device_make_bus_id(). It has the following comment:
> 
>  * This routine will first try using either the dcr-reg or the reg property
>  * value to derive a unique name.  As a last resort it will use the node
>  * name followed by a unique number.
> 
> Since the gpio_keys node does not have a reg properties, it gets a
> unique number appended to it. We end up with the device name
> "gpio_keys.3"
> 
> So as it stands, it does not appear i can make the DT system use the
> same device name as a board system.
> 
> But i'm also a little bit concerned by the "unique number" and this
> ending up in /dev/input/by-path/platform-gpio_keys.3-event. Is this
> path supposed to be stable? This unique number is not stable. An
> unwitting change to the DT could cause its value to change. Do we need
> to make it stable?
> 

One possibility would be to create an artificial bus in DT for all
gpio-keys devices, use #address-cells=<1> and #size-cells=<0>
for it, and give each device a unique reg property. Not sure if that
would be considered an elegant solution though.

	Arnd