Set GPIO at boot on Raspberry Pi

[Toby]

On 20/12/15 18:42, Ian Lepore wrote:

> But I don't think pin state when changing config is quite what Toby was
> asking; he needs a way to configure driven pins very early in boot.

Yes, that was my question.

> Right now we have no way of preconfiguring gpio pins to be driven a
> certain way early in boot.  By manipulating the device-tree data you
> can configure a pin as input or output, and usually you can configure
> pull up/down values for inputs, but there's no standard device-tree
> syntax to configure the drive value when configuring a pin to be
> driven.

Can you be a bit more specific on how I would do that?

> Maybe we could add some dev.gpioc tunables so that pins could be
> configured via loader.conf.

That's what linux has, setting max_usb_current=1 in their
/boot/config.txt sets GPIO38 to high. I don't know if they have a
generic way of configuring pins though.

Thanks,
Toby