Re: RE: on-ness

[Dominik Brodowski <linux@dominikbrodowski.net>]

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On Fri, Apr 21, 2006 at 11:30:05AM -0700, David Brownell wrote:
> > > > Well, the big problem with names and anything "system specific" is that it
> > > > makes _abstractions_ harder. It makes userspace's life harder, as it needs
> > > > to know what "idle" means on a specific system, instead.
> > > 
> > > If by "userspace" we can mean just "what writes the /sys/power/state file",
> > > it's straightforward for a given system to provide mappings between some
> > > common tokens ("standby", "mem", etc) to a system-specific meaning.
> > 
> > Uh. Not /sys/power/state. But /sys/devices/...../power/{[a],[b],[c]} where
> > [a], [b] and [c] need sensible names.
> 
> Well, "on" could have one defined meaning.  Maybe it's the only option
> available, until drivers add intelligence.  I don't see any problem
> with the other names being system-specific, since it's rather unlikely
> that a PCI_D3hot state will ever appear on most embedded ARM boxes.
> And if any userspace code tries to set power states, it had darn well
> better understand exactly what's going on.

Yes. However if a network managing userspace code wants to set the power
conusmption of a WLAN device to the lowest possible setting, it shouldn't
need a configuration file specific for each platform.

> > Yes. That's why there is talk about having different files describing a
> > device, and not just one. So you might have four files describing these four
> > clocks... and yet another file for describing the non-working states.
> 
> That seems too complicated to me.  When debugging, I want to visualize the
> entire tree ... so I'd want a /sys/kernel/debug/clocktree file, with lots
> of system-specific information.  (Which gate bits are set/cleared?  What
> speeds? etc.)  Or else I just want to know which state the driver is in,
> like "mostly one".  Some of that is taste, but also don't forget that each
> attribute in sysfs has a cost.

Uh, there's a rule "one-value-per-file" for sysfs. Arrays might be OK in
certain cases, but lots of system-specific information in one file? No way,
IMHO.

Thanks,
	Dominik

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