Oliver Neukum wrote: > Am Montag 05 Mai 2008 11:51:03 schrieb Alan Jenkins: > >> Oliver Neukum wrote: >> >>> Am Samstag 03 Mai 2008 14:36:48 schrieb Alan Jenkins: >>> >>>> I don't think that should count as an "active" device. That's about as >>>> much as I can help. I suggest you ask the linux-usb-users mailing list >>>> - someone referred me there when I was asking about this sort of thing, >>>> and they were pretty responsive and helpful. >>>> >>> Any USB device that is not explicitely suspended is active. With the >>> exception of hubs USB devices are not suspended unless their driver >>> and user space via sysfs request it. >>> >> But in this case there is no driver. With linux, you have to have a >> driver, e.g. for charging a Blackbery via USB; if it has no driver at >> all then it wouldn't be powered - no? Surely if a device without >> > > This turns out not to be the case. > That explains it then. Thanks for the correction >> drivers isn't considered to require power, then it shouldn't be >> considered to be active? Or is this an illogical quirk of the UHCI >> hardware? >> > > In a way. UHCI needs to do DMA. But many devices crash when suspended. > So the kernel refrains from doing so unless told otherwise. > OK. So there could be bad side effects (buggy fingerprint reader starts flashing a backlight annoyingly, or kills the bus, or something). Also if you had a driver but needed to bind it manually / start it in userspace, then the kernel would have crashed the device before you could do anything with it. I had only thought about autosuspend breaking devices while you were using them. >> Are you suggesting that Sascha and others need to identify all the >> devices without drivers hanging off their USB bus and de-"activate" them >> in sysfs, i.e. >> >> echo "suspend" > power/level >> > > I am suggesting that. Or rather that they use "auto" instead of > "suspend" > But if you use "auto", then you have to wait for the timeout (as set in the autosuspend file), and the driver has to support it to some extent, right? If you can't use the device anyway because there's no driver, I'd have thought it's simpler to try forcing it to suspend, rather than fiddling with autosuspend.
I mentioned earlier that I couldn't get my USB keyboard to autosuspend, but I could suspend it manually (on 2.6.24.4). I assume the usb_hid driver doesn't support autosuspend. So you're saying autosuspend will work when there's no driver to veto it (assuming the hardware doesn't crash)? Thanks Alan _______________________________________________ Discuss mailing list [email protected] http://mail.lesswatts.org/mailman/listinfo/discuss
