On Mon, Apr 08, 2013 at 08:57:43AM -0700, Sarah Sharp wrote: > On Mon, Apr 08, 2013 at 06:29:36AM -0700, Greg KH wrote: > > On Mon, Apr 08, 2013 at 08:58:09PM +0800, Lan Tianyu wrote: > > > On 2013/3/30 4:24, Alan Stern wrote: > > > >On Fri, 29 Mar 2013, Sarah Sharp wrote: > > > > > > > >>>Also, bear in mind that the proposed patch does not give userspace a > > > >>>way to power off ports via usbfs. What the new code does is a > > > >>>power-off reset -- it turns off power to the port, waits a short time, > > > >>>and then turns power back on. > > > >> > > > >>I think we need two separate IOCTLs: turn off the port power and turn it > > > >>on. Then we get the manual port power off for our QA testing, distros > > > >>can make interesting policies about manually powering off ports, and > > > >>userspace can choose how long they want the port to be off. After all, > > > >>different devices may need a longer powered-off period than others. > > > > > > > >Or one port-power IOCTL that takes the setting as an argument. Yes, > > > >this would be more flexible than a power-off reset. > > > Hi Alan & Sarah: > > > I just recall why I put power off and power on in one ioctl. > > > At first, I also tried to make power on and power off into two ioctls. > > > But I found after powering off a device, the usbfs device node will > > > be removed and so can't power on the port via the same usbfs node. > > > > > > For this point, we should add usbfs node for usb port? > > > > No. > > I agree that we shouldn't add more usbfs files without thinking very > carefully about it, since lots of tools like libusb use them. However, > we do need a way to manually power off a port, wait a variable length of > time (or perhaps for a distro-specific event like screen unblank), and > turn the port on. > > So how do we turn the port power back on with the options we have? > Would userspace have to turn the port power off via usbfs, and then > manually back on by setting the port's sysfs power/control to 'on'? Whatever method we use, it should be the same interface for both on and off, so I would prefer to just use the sysfs one, as usbfs does not represent ports, only USB devices. greg k-h -- 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
