[LEDE-DEV] [PATCH 2/3] ramips-mt7621: add GPIO-config for Ubiquiti-EdgeRouterX(-SFP)

[Mathias Kresin]

07.05.2017 23:24, Sven Roederer:
> On Sonntag, 7. Mai 2017 12:25:39 CEST you wrote:
>> Just an opinion: being able to disable/enable PoE for each port is really
>> useful when you want to remotely reboot a device plugged into your PoE
>> switch/router.  Most PoE-capable devices expose this option with the stock
>> firmware.
>>
>> Does your approach with the gpio-export node allow to change the state of
>> the GPIO at runtime? (i.e. probably from userspace)
>
> Baptiste,
>
> right, that's the point I'm also looking for. To have da clean way of
> controlling the state of the PoE-voltage (24V passive PoE) for the ports.
> As it's passive PoE there might be a big risk that having the power enabled
> all the time might cause some problems.
>
> When defining in dts I don't see them in uci or even in /sys/class/gpio. So via
> "board.d/03_gpio_switches" seems the best way to bring them to userspace for
> user-interaction.

If you use the gpio-export node in the device tree source file, the gpio 
pin should appear at /sys/class/gpio/. Most likely you have done 
something wrong. Could it be that you used exactly the same gpio pin 
number as you have it in your 03_gpio_export file? You need to decrement 
the gpio pin number by the gpio base as it is done for all gpios in the dts.

Correct me if I'm wrong, but as far I can see (and confirmed by testing 
it) the exported gpio in UCI doesn't have any benefit for your restart 
usecase. If I change the gpio value via uci and restart 
/etc/init.d/system the gpio value is still the same. Means, the value is 
only set during the actual export (on boot).

Mathias