> > On Wed, Jul 17, 2013 at 10:36 AM, Peter Chen <peter.chen@xxxxxxxxxxxxx> > wrote: > > On Mon, Jul 15, 2013 at 11:31:17PM -0700, Greg KH wrote: > >> On Tue, Jul 16, 2013 at 11:49:07AM +0800, Rong Wang wrote: > >> > Hi Greg, > >> > > >> > The USB on our platform can change roles between HOST and GADGET, > but > >> > it is not capable of OTG. > >> > >> That kind of sounds like the definition of OTG :) > >> > >> > When the USB changes between roles the udev will run some scripts > >> > automatically according to the udev rules. > >> > >> What exactly does udev/userspace see when the roles change? > >> > >> And what can trigger the change in roles? > >> > >> > The default role is GADGET, and we bind the g_mass_storage to the > USB > >> > GADGET role. > >> > > >> > We should secure the back end file storage between the device and > the > >> > host PC connecting to our device. > >> > We need to know when the GADGET is really connect to a host PC, then > >> > we can umount the file on the device > >> > and export it to the g_mass_storage. > >> > >> I thought you already get an event for this, otherwise no one would be > >> able to properly deal with this. > >> > >> > The question is since we default GADGET, so the g_mass_storage.ko is > >> > installed early but connecting to a host PC > >> > is randomly, But the udev has no idea when a host PC connects our > device. > >> > > >> > So we consider it's reasonable to let the udev know the GADGET > device state. > >> > Is there any alternative to our question? > >> > >> I thought we already export events for gadget device states, have you > >> looked for them? I can't dig through the code at the moment, but this > >> seems like a pretty common issue... > >> > > > > If I understand correctly, what Rong wants is udev can be notified the > > udc state changes, like connect/disconnect event. Currently, we only > > export it to /sys. > > OK. Thanks for your share. > > And you develop a new utility rather than udev to monitor that file? > And you probably create a work queue in your udc driver to do this work? > Not yet, no one complains it, so I haven't added it. But, it is a useful user interface, Android has implemented similar functions at its gadget driver. Best regards, Peter -- 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
