Messages in this thread | | | Date | Thu, 25 Jul 2013 19:29:20 +0100 | From | Mark Rutland <> | Subject | Re: DT bindings as ABI [was: Do we have people interested in device tree janitoring / cleanup?] |
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On Thu, Jul 25, 2013 at 07:05:48PM +0100, Stephen Warren wrote: > On 07/25/2013 10:57 AM, Mark Rutland wrote: > > On Thu, Jul 25, 2013 at 05:09:19PM +0100, Olof Johansson wrote: > ... > >> So, there really seems to be a need for a layered approach, one in > >> which a binding "graduates" from being tentative to being locked in. > >> I'm refraining from using the terms "staging" and "stable" here, since > >> they have overloaded meaning in the kernel world that doesn't apply > >> here. > > > > I'm not sure how realistic it is to have drivers in the kernel using > > unstable bindings, and expect people to not rely on them, but I don't > > have a better option to give. We need a big fat warning that an unstable > > binding is in use. > > I don't think having people "rely" on the bindings is the issue so much > as the awareness that if they do, there will be compatibility issues for > unstable bindings.
As long as we can make sufficiently clear that trying to use an unstable binding is going to be *very* painful, and not necessarily supported.
> > >> One problem that needs to be solved is obviously how a binding > >> graduates from tentative to locked. This work isn't going to be very > >> interesting to most people, I suspect. Think standards committee type > >> work. > >> > >> A possible way to handle this is to have exactly that: A group of > >> people that essentially constitute the "standards committee" that meet > >> on a regular basis to review and approve new bindings. They should be > >> people not just doing ARM Linux work, but other stakeholders in these > >> bindings too. One of the things they should probably do is sift > >> through our current in-kernel bindings and select those who seem ready > >> to be locked in, review/discuss/decide upon that and once the decision > >> is made, that specific binding does become part of the static, > >> never-ever-change ABI of firmware-to-kernel interfaces. That might > >> also be the time that the binding is moved from the kernel to a > >> separate repo, but that's a technicality that we'll let the DT > >> maintainers decide among themselves, IMHO. > > > > We're going to need input from other OSs too, or the bindings will > > remain Linux-specific regardless of how far away the bindings and dts > > repo(s) is/are. > > And bootloaders too. Some U-Boot platforms are starting to use DT for > exactly the same reason that the kernel does; to allow a single > bootloader binary to run on a variety of different boards, with all > configuration coming from DT.
Ah, I'd not considered that. We certainly need to include them in the discussion.
> > On another related topic, something that may be useful for the DT > bindings reviewer team is a basic checklist for new DT bindings. > Something similar to Fedora's package review checklist. Perhaps also > (yet another?) document on a bit of DT philosophy. If this sounds > useful, I could try and take a stab at some basic initial version.
That does indeed sound useful. Please do :)
> > We also need to decide (or just document) exactly what "describes the > HW" means; see the thread on thermal limits, and consider the extension > of describing hard/absolute thermal limits to describing use-cased base > thermal profiles using the same schema, or not allowing that. >
Certainly. This is an unfortunate gray area.
Thanks, Mark.
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