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SubjectRe: devd and device events (was Re: My $0.02 on devd and devfs)
Jeff Garzik wrote:
>
> "H. Peter Anvin" wrote:
> > David Harris wrote:
> > > > Depending on the kind of daemon used, it would either be respawned or
> > > > the info would get queued up until it is restarted. I don't think it's
> > > > particularly anything to worry about, though...
>
> > > If you re-spawn the daemon and it gets to see all of the events that have been
> > > stored up, it still does not have a proper view of the device configuration.
> > > The kernel really has to be smarter than just issuing events and buffering
> > > them.
>
> > It doesn't have to -- the additional information it needs is in the file
> > system.
>
> It doesn't have to, yes, but scanning the fs would be ugly and probably
> time consuming.
>
> IMHO /proc/device_events should be an ASCII list of device events, like
> described previously in this thread. Each line in that list, though,
> would need a timestamp of some sort.
>
> devd then maintains its own state, [optionally] syncing up after a
> restart using the timestamps to handle as-yet-unprocessed events. This
> allows for any amount of time to pass between kernel bootup and devd
> doing its work.
>
> To continue along this train of thought: any suggestions for creating
> /proc/device_events? Presumeably stealing code from PCMCIA would be a
> good place to start.
>

I don't believe that devd *needs* to keep this kind of state, however.
I'm actually pretty sure it doesn't. That's why I would start by
working on the daemon, and feed it simulated data, before implementing
the kernel interface -- then I'd know better what the requirements
really are, and what the smallest possible implementation would look
like.

-hpa

--
<hpa@transmeta.com> at work, <hpa@zytor.com> in private!

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