Re: Question regarding back compatibility for DT

On Tue, Mar 21, 2017 at 11:16 AM, Warner Losh [off-list ref] wrote:

On Tue, Mar 21, 2017 at 8:58 AM, Daniel Lezcano
[off-list ref] wrote:

quoted

Hi Rob, dt people,

is it acceptable a driver is changed using a new DT binding but becomes
incompatible with the old DT files ?

IOW, is it possible to change the DT and the driver without supporting the old
DT format, forcing an update of the DT and the kernel ?

I've seen new properties many times added, even though the new driver
wouldn't work quite right on old DT files. I've also seen people
create a new hardware compatibility name for a totally new binding.
Finally, I've seen the bindings just randomly change for no reason
with no concern for backwards compat. The last really sucks if you
have a driver that's not in the Linux tree (say, because it's a
FreeBSD driver).

Hopefully that is getting better? If not, how do we make it better? I
try to prevent it through reviews, but I have have no visibility into
what FreeBSD does and doesn't care about.

The common suggestion is moving the bindings out of the kernel. The
biggest issue I have with that is that we would lose the review of all
the kernel subsystem maintainers. They may be biased toward Linux, but
they know their class of h/w and no other project has the breath of
h/w support.

Rob
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