Re: CVS commit: src/sys/dev/i2c

[Jared McNeill <jmcneill%invisible.ca@localhost>]

On Tue, 29 Aug 2017, Manuel Bouyer wrote:

> I'd like to have a way to disable this (a compile-time option would be OK
> for me).
>
> On evaluation boards (like cubieboard, or olimex lime2), you may have
> a power button on the board itself but you don't have a way to add an external
> power button (e.g. if you put the board in a case), so once powered off
> you have to power-cycle it.

I'm not opposed to having a compile time option or sysctl -- but if we do 
I think we should try to make it MI. In theory an ACPI capable x86 board 
could have this problem as well..

For axp specifically I think the right place to put it would be as a 
properly for the PMIC node in the device tree to disable poweroff. This 
way we can set it on a per-board basis. I didn't see one in the current 
binding docs, so we'd want to coordinate with the linux-sunxi folks on that.

> For a personnal project (for those curious, available at
> https://github.com/mbouyer/marine_chartplotter) I embeeded a olimex lime2
> in a case, along with a power/interface board. I did develop a driver for
> the external power controller, and in such a case I don't want the
> power hook of the axp20x to be called. I don't think this use case is
> uncommon ...

Looking at your driver:

https://github.com/mbouyer/marine_chartplotter/blob/master/software/NetBSD/driver/picbmc.c#L137

By taking over cpu_powerdown_address this will bypass the FDT hooks, so 
you should be ok here.

Cheers,
Jared