[RFC] Device Tree Overlays Proposal (Was Re: capebus moving omap_devices to mach-omap2)

[Koen Kooi]

Op 10 nov. 2012, om 00:40 heeft Grant Likely <grant.likely at secretlab.ca> het volgende geschreven:

> On Fri, Nov 9, 2012 at 11:23 PM, Stephen Warren <swarren at wwwdotorg.org> wrote:
>> On 11/09/2012 09:28 AM, Grant Likely wrote:
>>> On Tue, Nov 6, 2012 at 10:37 PM, Stephen Warren <swarren at wwwdotorg.org> wrote:
>> ...
>>>> I do rather suspect this use-case is quite common. NVIDIA certainly has
>>>> a bunch of development boards with pluggable
>>>> PMIC/audio/WiFi/display/..., and I believe there's some ability to
>>>> re-use the pluggable components with a variety of base-boards.
>>>> 
>>>> Given people within NVIDIA started talking about this recently, I asked
>>>> them to enumerate all the boards we have that support pluggable
>>>> components, and how common it is that some boards support being plugged
>>>> into different main boards. I don't know when that enumeration will
>>>> complete (or even start) but hopefully I can provide some feedback on
>>>> how common the use-case is for us once it's done.
>>> 
>>> From your perspective, is it important to use the exact same .dtb
>>> overlays for those add-on boards, or is it okay to have a separate
>>> build of the overlay for each base tree?
>> 
>> I certainly think it'd be extremely beneficial to use the exact same
>> child board .dtb with arbitrary base boards.
>> 
>> Consider something like the Arduino shield connector format, which I
>> /believe/ has been re-used across a wide variety of Arduino boards and
>> other compatible or imitation boards. Now consider a vendor of an
>> Arduino shield. The shield vendor probably wants to publish a single
>> .dtb file that works for users irrespective of which board they're using
>> it with.
>> 
>> (Well, I'm not sure that Arduino can run Linux; perhaps that's why you
>> picked BeagleBone capes for your document!)
> 
> Correct, the Arduino is only an AVR with a tiny amount of ram. No Linux there.
> 
> However, Arduino shields are a good example of a use case. I think
> there are even some Arduino shield compatible Linux boards out there.

A good example of those would be the Rascal Micro: http://rascalmicro.com/

regards,

Koen