On Fri, 16 May 2014, Miner, Blake wrote: > > I am not sure about this, but I wonder can we do the reset in > > cp210x_open() instead of in cp210x_startup()? > > Possibly, but I'd rather perform the reset just once, right when the > device is detected and bound to the driver. After doing some more > reading, I've found that calling `usb_lock_device_for_reset` just > before `usb_reset_device` seems to work. Here's a possible patch: > > --- cp210x.c > +++ cp210x.c.new.c > @@ -856,7 +856,8 @@ > struct cp210x_serial_private *spriv; > > /* cp210x buffers behave strangely unless device is reset */ > - usb_reset_device(serial->dev); > + if(usb_lock_device_for_reset(serial->dev, NULL) == 0) > + usb_reset_device(serial->dev); > > spriv = kzalloc(sizeof(*spriv), GFP_KERNEL); > if (!spriv) > > The downside here is that the reset takes a few hundred extra > milliseconds, and the reset is issued for each interface. But, at > least both interfaces are properly detected the first time. :) Any > thoughts? If you lock a device, you have to unlock it later. Read the kerneldoc in the definition of usb_lock_device_for_reset() to see how it works. 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
