On Wed, 10 Aug 2005, Vlado Handziski wrote: > > In principle, we could add an interface to the hub driver allowing > > userspace to ask that certain ports be left powered off (and also that > > ports be powered back on). This could be done using sysfs or ioctl; it > > doesn't fit all that well into the usbfs framework. ioctl would probably > > be simpler. > > Yes, this would be an option. But the possibility of a user going > around the hub driver (as we do) and being "surprised" by the > self-healing logic remains. In these cases, using the hardware as > storage of the state might be the best. If the hub is properly > configured (valid descriptor, etc.) _and_ some of the port power > status bits are cleared, this should be clear evidence of intent on > the side of the user to power down this port so the healing should not > be applied. So the hub code can just test the state of the hardware > and make this decision.
If memory serves, that self-healing logic was added precisely because some hubs _don't_ preserve the hardware state correctly. They may spontaneously lose power under certain conditions. So that code cannot simply be removed. Alan Stern ------------------------------------------------------- SF.Net email is Sponsored by the Better Software Conference & EXPO September 19-22, 2005 * San Francisco, CA * Development Lifecycle Practices Agile & Plan-Driven Development * Managing Projects & Teams * Testing & QA Security * Process Improvement & Measurement * http://www.sqe.com/bsce5sf _______________________________________________ linux-usb-devel@lists.sourceforge.net To unsubscribe, use the last form field at: https://lists.sourceforge.net/lists/listinfo/linux-usb-devel
