Re: [Ksummit-2013-discuss] DT bindings as ABI [was: Do we havepeople interested in device tree janitoring / cleanup?]

From: David Woodhouse
Date: Fri Jul 26 2013 - 09:41:23 EST

On Fri, 2013-07-26 at 09:27 -0400, Jason Cooper wrote:
> The other dynamic change that bears mentioning here is attributes which
> have been configured by the bootloader. For example, in mvebu, we have
> the Schrodinger's Cat register. It allows you to reconfigure the base
> address of the registers from *within* that register range. If the
> bootloader does this, the DT needs to be updated to reflect the current
> hardware configuration. Otherwise, the kernel is stuck poking around at
> memory addresses hoping to find something sane.
> But this falls into the same category as you mentioned, but outside of
> chosen {};.

Yeah, /chosen was given as an example of stuff that's almost
*exclusively* "configuration" stuff.

But there's plenty outside there that can reasonably change.

It's OK to change the data, and of *course* the base address reported in
the DT should actually match reality *today*, if it changes on the fly.

It's not OK to change the *schema* in which those data are expressed.
That's the ABI we're talking about.


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