On Mon, Feb 02, 2009 at 01:36:26PM -0800, Paul Zimmerman wrote: > Hi Sarah, > > I think the issue on the gadget side, is that a USB3 device will want to > support connecting to a USB2 host too. So whatever changes are added to the > gadget code for USB3, it must be possible to dynamically switch to either > USB2 or USB3 mode, depending upon the type of host detected. Sure, that makes sense. It should be similar to how current gadget devices handle switching between LS/FS/HS. ISTR that a USB 3.0 device must implement one of the slower speeds (LS/FS/HS), but it is up to the device which one it supports. So any new code to switch between speeds would have to take that into account. Dave Brownell, is there common infrastructure for speed switching in the gadget core, or is it on a per-PCD basis? Sarah Sharp > -- > Paul > > -----Original Message----- > From: Sarah Sharp [mailto:sarah.a.sharp@xxxxxxxxxxxxxxx] > Sent: Monday, February 02, 2009 1:26 PM > To: Viral Mehta > Cc: Kawshol Devilal SHARMA; David Brownell; John Youn; Paul Zimmerman; Joel Gotesman; sridharan.ranganathan@xxxxxxxxx; David Vrabel; linux-usb@xxxxxxxxxxxxxxx > Subject: Re: USB 3.0 gadget stack > > On Sat, Jan 31, 2009 at 12:08:49PM +0530, Viral Mehta wrote: > > > >> Of course these changes discussed don't even cover the new link power > >> management and function suspend for USB 3.0 devices. Those will both be > >> a requirement for USB 3.0 device compliance, but we can discuss those > >> after we have an idea of the changes necessary for basic USB 3.0 > >> gadget-side support. > >> > >> Can anyone think of any other changes for USB 3.0 gadget side support? > >> > > I still do not understand how exactly core and gadget side driver or > > controller or peripheral controller will address > > backward/forward compatibility issues. > > > > Like USB3.0 device can be attached to USB2.0 bus and USB2.0 devices can > > be attached to USB3.0 bus. > > A USB 3.0 device attached to a USB 2.0 port will show up as a USB 2.0 > device. The USB 3.0 device will not see the USB 3.0 terminations and > will just enumerate as a USB 2.0 device with USB 2.0 device descriptors. > No support is necessary for that case, because the USB core knows how to > deal with USB 2.0 devices. > > For the case of a USB 2.0 device plugged into a USB 3.0 port (under > xHCI, presumably), there will need to be some changes to support the > xHCI driver. Those changes are part of my xHCI host controller > patchset. > > Sarah > -- > 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 -- 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
