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Date:   Sun, 3 Nov 2019 17:22:41 +0100
From:   Maxime Ripard <mripard@kernel.org>
To:     Karl Palsson <karlp@tweak.net.au>
Cc:     "linux-arm-kernel@lists.infradead.org" 
        <linux-arm-kernel@lists.infradead.org>,
        Linux Kernel Mailing List <linux-kernel@vger.kernel.org>,
        "wens@csie.org" <wens@csie.org>
Subject: Re: [PATCH 3/3] ARM: dts: sun8i: add FriendlyARM NanoPi Duo2-IoT Box
Message-ID: <20191103162241.GE7001@gilmour>
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On Fri, Nov 01, 2019 at 09:55:41AM -0000, Karl Palsson wrote:
>
> Maxime Ripard <mripard@kernel.org> wrote:
> > On Thu, Oct 31, 2019 at 11:12:16PM +0000, Karl Palsson wrote:
> > > The IoT-Box is a dock for the NanoPi Duo2, adding two USB host ports, a
> > > 10/100 ethernet port, a variety of pin headers for i2c and uarts, and a
> > > quad band 2G GSM module, a SIM800C.
> > >
> > > Full documentation and schematics available from vendor:
> > > http://wiki.friendlyarm.com/wiki/index.php/NanoPi_Duo2_IoT-Box
> > >
> > > Signed-off-by: Karl Palsson <karlp@tweak.net.au>
> >
> > It seems like it's something that can be connected /
> > disconnected at will?
> >
> > If so, then it should be an overlay, not a full blown DTS.
>
> Fine with me, I wasn't sure on the best procedure for things like
> this. It's not something you plug / unplug at run time, you'd
> tend to just always have this, or not. Is it best to just have
> user space distributions handle selecting the overlay then? and
> they maintain the overlay file?

Another option would be to do it at the bootloader level, based on a
discovery mechanism (eeproms storing data / the overlay itself, the
presence of some devices on buses that you can probe (i2c, mmc, etc).

> I'd considered overlays something for _per user_ customization,
> but I'm perfectly happy if it it's intended to be used for per
> product customization too if that's the right method.

Overlays are for dynamic configuration. The user customization is one
of its use case, but add-on boards are another (being used by the RPi
and the Beaglebones), just like FPGA configuration for example.

Maxime

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