[systemd-devel] Udev rules hardware database

[Oliver Neukum]

On Sun, 2014-11-09 at 22:39 +0100, Patrick Häcker wrote:
>  
> > I really don't know.  Some other operating system relies on a whitelist
> > due to all of the horrible devices out there that can't handle suspend
> > (keyboards and mice are notorious for being bad.) 
> 
> Thanks for your input. Do you know in which kernel version the above 
> mentioned bug got fixed?
> I just checked two mice, a keyboard and a bunch of internal devices with a 
> 3.17 kernel. Only one of the mice works completely reliable with activated 
> power saving as input device – no problems with the internal devices. The 
> funny thing is: That mouse is built from the same company as some other 
> operating system – dog feeding does make sense.

The problem with mice is the usual inability to trigger a remote wakeup
when the mouse is moved. They only do a remote wakeup when a button
is pressed. (The behavior is within spec. The USB HID spec is
deficient.)
I took two lessons from that

1. It makes no sense to use the same approach for all USB devices.
Some classes need a blacklist others do need a whitelist.

2. The kernel is not really the ideal place to decide when to activate
power management. Most mice are built for an operating model which
has more grades then Linux usually uses. We see our system either as
fully operational or suspended. Those mice are built for reducing power
consumption when a system becomes "unused" and the screen is blanked
or the screensaver comes up.

> > You might want to ask one of the distro people to see if they have ever
> > turned it on "by default" and what happened if they tried that.
> Unfortunately, I do not know anyone from a distribution who is in charge for 
> that area. Do you? A short Google search didn't bring up any distribution 
> which did that, but my search was probably incomplete.

Unlikely. You end up with systems that are practically unusable in the
worst and commonest case.

> But if my results mentioned above should be remotely representative, that 
> might be disastrous, because for an average user it might be close to 
> impossible to deactivate power savings without working input devices.

Exactly.

	Regards
		Oliver