On Mon, Jul 31, 2017 at 8:11 AM, David Gibson <david@xxxxxxxxxxxxxxxxxxxxx> wrote: > On Fri, Jul 28, 2017 at 10:07:10AM -0500, Rob Herring wrote: >> On Fri, Jul 28, 2017 at 7:23 AM, Pantelis Antoniou >> <pantelis.antoniou@xxxxxxxxxxxx> wrote: >> > Hi Rob, >> > >> > On Thu, 2017-07-27 at 21:12 -0500, Rob Herring wrote: >> >> On Thu, Jul 27, 2017 at 7:51 PM, Tom Rini <trini@xxxxxxxxxxxx> wrote: >> >> > On Thu, Jul 27, 2017 at 06:00:00PM -0500, Rob Herring wrote: >> >> >> On Thu, Jul 27, 2017 at 4:46 PM, Pantelis Antoniou >> >> >> <pantelis.antoniou@xxxxxxxxxxxx> wrote: >> >> >> > Hi Frank, >> >> >> > >> >> >> > On Thu, 2017-07-27 at 13:22 -0700, Frank Rowand wrote: >> >> >> >> Hi Pantelis, >> >> >> >> >> >> >> >> Keep in mind one of the reasons Linus says he is very direct is to >> >> >> >> avoid leading a developer on, so that they don't waste a lot of time >> >> >> >> trying to resolve the maintainer's issues instead of realizing that >> >> >> >> the maintainer is saying "no". Please read my current answer as being >> >> >> >> "no, not likely to ever be accepted", not "no, not in the current form". >> >> >> >> >> >> >> >> My first reaction is: no, this is not a good idea for the Linux kernel. >> >> >> >> >> >> >> > >> >> >> > This has nothing to do with the kernel. It spits out valid DTBs that the >> >> >> > kernel (or anything else) may use. >> >> >> >> >> >> Let me rephrase Frank's statement: this is not a good idea for the >> >> >> main repository of dts files. >> >> >> >> >> >> But sure, DTS is already not the only source of DTBs. It comes from >> >> >> firmware on Power systems. >> >> > >> >> > Yes, but unless they're generated from something other than a (at the >> >> > time) normal DTS, that's not a good example, IMHO. >> >> >> >> They aren't. I'm talking about IBM systems. The firmware has its own >> >> representation and flattens that to a DTB is how I understand it. >> >> >> >> >> If you want to create and maintain your own >> >> >> source format, then that is perfectly fine. But based on the current >> >> >> understanding, I'm not seeing a reason we'd convert DTS files to YAML. >> >> > >> >> > Can I propose one? To borrow a phrase, Validation, Validation, >> >> > Validation. Let me point to fe496e23b748 in the kernel for a moment. I >> >> > found that as part of helping a new engineer come up to speed on doing >> >> > device tree work. What I found was a case where: >> >> > - The binding doc gives one value for compatible as the required value. >> >> > - The code accepts only a single, different value. >> >> > - A few in-kernel dts files have different still values. >> >> > >> >> > If the common dts source file was in yaml, binding docs would be written >> >> > so that we could use them as validation and hey, the above wouldn't ever >> >> > have happened. And I'm sure this is not the only example that's in-tree >> >> > right now. These kind of problems create an artificially high barrier >> >> > to entry in a rather important area of the kernel (you can't trust the >> >> > docs, you have to check around the code too, and of course the code >> >> > might have moved since the docs were written). >> >> >> >> I'm all for validation, but the binding doc or schema and files that >> >> describe platforms (aka DTS files) are not the same thing. The schema >> >> is what are the constraints for a binding. Maybe some bindings are >> >> fixed where there's only one valid binding implementation, but that's >> >> the easy case (we could use DTS for that). I'll take YAML for binding >> >> docs yesterday. Believe me, I'm tired of reviewing free form binding >> >> docs. If that's where you want to go, reply to my reply that went >> >> unanswered on Matt Porter's YAML proposal from 2 years ago (or maybe 3 >> >> now). I had the whole binding doc tree converted over to an initial >> >> YAML schema. We just need to agree on the schema. Or we can keep >> >> waiting for Grant to publish what he started on... >> >> >> > >> > The way I see it there's a validation hierarchy. >> > >> > There are the bindings that describe the schema of the resulting source >> > files. The bindings must be validated against a binding schema. >> > >> > For the source files, at first they must be valid against the core >> > language (i.e. DTS or DT YAML variant) schema. >> > >> > Next for each node that a binding exists in a valid format, it must be >> > validated against it. I.e. if an interrupt property exist it must point >> > to valid interrupt node etc. >> > >> > Up next a number of per-platform/configuration validation passes. >> > I.e. for a complete source file which is using a specific SoC family >> > i.e. "ti,am33xx" the pass may verify that for the given peripherals >> > their configuration is correct, i.e. that the interrupt numbers for a >> > given peripheral are the correct ones for the target board etc. >> > This may be possible by having a golden master configuration when those >> > number can be retrieved and compared against. >> > >> > Finally you could have a per-application/vendor/end-user final rule >> > check, i.e. the regulators may be configured in a manner that the power >> > consumption is under some specified threshold, etc. This is something >> > that is completely out of the kernel scope, but may have have to >> > vendors. >> > >> > Why don't you share what you've been working on and see what we can do >> > using it as a base? >> >> I did. 2 years ago: >> >> https://git.kernel.org/pub/scm/linux/kernel/git/robh/linux.git/log/?h=dt-yaml-v2 >> >> It's very rough, but I was at the point of wanting feedback on the >> schema format. Only the crickets gave me any. >> >> It doesn't validate anything, but is purely binding docs mass >> converted to YAML using DTS files as input. > > Efforts on schemas have started and petered out several times :(. > > I think the fundamental problem is that there just isn't critical mass > of people with the time to work on it. Lots of people want better > validation, but not enough to put significant time and effort into > it. I hope someone proves me wrong about that. I would say part of the problem is the validation plans are always just too grand. We need to start small. Just having a machine parseable documentation format alone would be a win. The validation can come later IMO. It's going to come later anyway if we do nothing. > Can I suggest (again) that one approach might be to add more pieces to > dtc's "checks" system to at least look for the more common errors. > It's not nearly a complete solution, but it gets you something with > much less difficulty than defining a whole schema system. Some > rudimentary checking of unit addresses has been added relatively > recently, but not a lot else in the way of semantic checks. Yes, I obviously agree. And at least for me, it's in a language I already know. I've thought of a few more checks to add in the course of this thread. Perhaps we should start a todo list if you have any specific ideas. I've focused on things I repeatedly catch in binding reviews (if only I could have a check for needing more specific compatible strings :) ). Where we hit limits with the checks is when we need specific compatible(s) to key checks on. This is any binding that lacks a "class" property like gpio-controller or interrupt-controller. For example I2C or SPI controllers and buses. Certainly every common binding with a #*-cells property could have some level of checks. Rob -- To unsubscribe from this list: send the line "unsubscribe devicetree" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
