Re: [Ksummit-discuss] Self nomination

["Rafael J. Wysocki" <rjw@rjwysocki.net>]

On Wednesday, August 03, 2016 10:12:00 AM Marek Szyprowski wrote:
> Dear All,
> 
> 
> On 2016-08-03 01:00, Rafael J. Wysocki wrote:
> > On Tuesday, August 02, 2016 10:09:17 AM Linus Walleij wrote:
> >> On Thu, Jul 28, 2016 at 12:14 PM, Marc Zyngier <marc.zyngier@arm.com> wrote:
> >>> On 26/07/16 23:30, Dmitry Torokhov wrote:
> >>>> - I would like to sync up with people and discuss [lack of] progress
> >>>>    on topic of device probe ordering (including handling of deferred
> >>>>    probes, asynchronous probes, etc).
> >>> I'm extremely interested in discussing this.
> >> I've also tried to pitch in on it in the past but I just feel stupid
> >> whenever we try to come up with something better than what
> >> we have :(
> >>
> >>> It has wide reaching consequences as (with my irqchip maintainer hat on)
> >>> we've had to pretend that some bits of HW (timers, interrupt
> >>> controllers) are not "devices". Not a massive issue for most, except
> >>> when your interrupt controller has requirements that are very similar to
> >>> the DMA mapping API (which you cannot use because "not a device"). Other
> >>> problems are introduced by things like wire-MSI bridges, and most people
> >>> end-up resorting to hacks like ad-hoc initcalls and sprinkling deferred
> >>> probes in specific drivers.
> >> Same feeling here. I'm accepting patches for random initcall
> >> reordering because there is nothing else I can do, people need to
> >> have their systems running. But it feels really fragile.
> >>
> >> Deferred probe alleviated the problem, but I remember saying at
> >> the time that what we really need to do is build a dependency
> >> graph and resolve it the same way e.g. systemd does. (Someone
> >> may have called me BS on that, either for being wrong about everything
> >> as usual or because of mentioning systemd, I don't know which one.)
> >>
> >> The latest proposal I saw came from Rafael and he had a scratch
> >> idea for a dependency graph that I really liked, but I guess he's been
> >> sidetracked since. Rafael, what happened with that?
> > I got distracted, but Marek Szyprowski has revived it recently.
> >
> > It needs to be cleaned up somewhat, but other than that I think it's in
> > a good enough shape to make some progress in that direction, at least in
> > principle.
> 
> I really like the idea of pm dependencies between device and the patches
> prepared by Rafael. They are exactly what we need for our case (PM for
> Exynos IOMMU), but they will also help solving PM issues with complex
> devices (like DRM for SoCs and ASoC audio).
> 
> Rafael: do you plan to do any update on them?

Yes, I do, but to make some cosmetic changes rather.

> Some time ago you wrote, that you had such plan, but real life proved
> something else.

Well, I was working on other things in the meantime, but I still had that
plan. :-)

> If needed I can continue works on them, but I need some directions what has
> to be improved and fixed.

Thanks so much!

First off, the networking people claimed the "devlink" term in the meantime
and it's better to avoid confusion here, so I'd change it to "devdep" or
similar in the patches.

In addition to that Tomeu Vizoso complained that the supplier_links and
consumer_links list heads in struct device were confusing and I see why that
could be the case, so I'd change them to something more direct, like maybe
links_to_suppliers and links_to_consumers.

Please let me know what you think.

Thanks,
Rafael