On Sat, 1 Aug 2009, Oliver Neukum wrote: > Am Samstag, 1. August 2009 07:15:44 schrieb Arjan van de Ven: > > > There were several different proposed kinds of autosuspend for USB mass > > > storage. None of them proved to be sufficiently safe and acceptable to > > > the community. > > > > fwiw the device I care about most is a SD card reader, and most of all, > > when there is no card in the device. > > Alan, > > now that I think about it this use case uncovers a deficiency in the > autosuspend algorithm. > We basically assume that the likelihood a device is used again > in the near future declines with the time a device is not used. In this > use case the opposite is true. If a device finds that no medium > is present, user space has no reason to use this device immediately > again, but it may try again in the future when a medium might be present > again. > I think we should have a hook for suspending a device right now > from a driver that knows that the device will not be used right now. Rafael's runtime PM implementation does have such hooks. In fact, it's missing the autosuspend delay that USB has -- it leaves all such delays up to the bus subsystem and device driver. 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
