On Thu, 12 Jan 2012, Oliver Neukum wrote: > Am Mittwoch, 11. Januar 2012, 23:36:25 schrieb Sarah Sharp: > > > Ok, that's what I thought. Some folks were concerned about bad system > > power management they have been seeing, and they were claiming the host > > didn't need to poll an empty CD drive if the USB CD drive advertised > > remote wakeup in its descriptors. Now I can tell them it's simply not > > true. > > But there still is an inefficiency with respect to polling devices. > If sd_open() fails with -ENOMEDIUM we go through the full > timeout. This is exactly what we shouldn't do in case a device > is polled at a regular frequency. What's needed is two different autosuspend timeouts; one for use when media is present and one for when it isn't. Or maybe we should call pm_runtime_dont_use_autosuspend when there's no media, which would effectively set the timeout to 0. For CDs it won't make any difference because sr doesn't support autosuspend anyway. It could be added without too much work, however. Alan Stern -- To unsubscribe from this list: send the line "unsubscribe linux-usb" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
