On Wed, 24 Jan 2007, David Brownell wrote: > > > > > I don't know, it just really annoys me to see that power directory there > > > > with no use for it for a lot of devices :) > > > > > > Would it help to add a flag somewhere in struct device (or struct > > > dev_pm_info) for indicating that the device is not cognizant of PM? > > If it would, the semantics would need to be clarified. Is the problem > that they can't suspend/resume at all? Or is the problem instead that > they (or their drivers) don't know how to do that without any loss of > functionality ... without a complete reset or whatever? The semantics I intended was that the flag should indicate the driver was completely ignorant of PM. It has no suspend or resume methods and no way of enabling or disabling remote wakeup. As is true, for example, of those USB endpoint pseudo-devices. Maybe this means the flag belongs in the driver's structure instead of the device's. But the PM core tries to avoid looking at drivers... > Most devices can -- if poked and prodded appropriately, and if no > BIOS or uploaded firmware interferes badly enough -- make it through > some kind of system suspend state. Whether that's the one the user > has chosen ... different issue! And whether the driver knows how to > do that ... also a different issue! > > But the specific problems we're seeing right now with the USB autosuspend > stuff relate to _runtime_ suspend. I believe some of them are just bugs > in the stack; where better coddling of the devices would let them make it > through unscathed. But some of them, likewise, probably _do_ have real > problems with real runtime suspend states (that don't map to "off"). That would be a separate issue. For now there's a (large?) set of devices whose drivers don't know Power Management from a hole in the wall. Alan Stern
