Messages in this thread | | | From | Oliver Neukum <> | Subject | Re: [linux-usb-devel] error to be returned while suspended | Date | Fri, 6 Oct 2006 09:21:51 +0200 |
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Am Donnerstag, 5. Oktober 2006 23:45 schrieb Alan Stern: > On Thu, 5 Oct 2006, Oliver Neukum wrote: > > > I have a few observations, but no solution either: > > - if root tells a device to suspend, it shall do so > > Probably everyone will agree on that.
But should it stay suspended until explictely resumed? Do we have consensus on that?
> > - the issues of manual & automatic suspend and remote wakeup are orthogonal > > Except for the fact that remote wakeup kicks in only when a device is > suspended.
Yes.
> > - there should be a common API for all devices > > It would be nice, wouldn't it? But we _already_ have several vastly > different power-management APIs. Consider for example DPMI and IDE > spindown.
No reason to make matters worse.
> > - there's no direct connection between power save and open() > > Why shouldn't a device always be put into a power-saving mode whenever it > isn't open? Agreed, you might want to reduce its power usage at times > even when it is open...
That and you are putting the latency/power choice into kernel space. I've seen GPS recievers that need 30 seconds to get a fix. Autosuspend needs to be in kernel space. But that doesn't mean that it is sufficient as a mechanism nor that it doesn't need parameters supplied from user space.
> > The question when a device is in use is far from trivial. > > Yes. It has to be decided by each individual driver. For simple > character-oriented devices, "open" is a good first start.
Yes. However, simple character devices are the first candidates for libusb so kernel space is left with the hard cases.
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