Request review of device tree documentation

[grant.likely@secretlab.ca (Grant Likely)]

On Mon, Jun 14, 2010 at 8:59 AM, Nicolas Pitre <nico@fluxnic.net> wrote:
> On Mon, 14 Jun 2010, David Gibson wrote:
>
>> On Sun, Jun 13, 2010 at 11:02:15PM -0600, Grant Likely wrote:
>> Indeed. ?In fact, the general rule of thumb is really "put as much as
>> possible into the most easily replaced layer of the stack". ?This is,
>> incidentally, why I've always been dubious about simple firmwares
>> supplying a flattened device tree rather than including the device
>> tree template in the kernel, cuboot style.
>
> The biggest advantage, IMHO, for adding DT to ARM, is actually to
> decouple the hardware config information and the kernel. ?If in the end
> the DT has to be shipped in the kernel then we're losing all this
> advantage over the current state of things on ARM which still works
> pretty well otherwise.
>
> In the best case, the simple firmware simply has to retrieve the
> flattened device tree from flash, and pass it to the kernel just like
> some anonymous blob. ?And the simple firmware only needs to provide a
> way for that DT blob to be updatable, like through an upload of a
> replacement blob that was prepared offline. ?Just like a ramdisk image
> or the like.
>
> That doesn't need to be fancier than that, and the goal of having the DT
> data tied to the hardware instead of the kernel is achieved.

exactly right.

g.