On Mon, 11 Feb 2008, Pandita, Vikram wrote: > >> 2. What is the "device address" used for in QH? > > > >There is no "device address" field in a QH -- at least, there isn't in > >uhci-hcd or ehci-hcd. Maybe other controller drivers do have such a > >field. > > I have a doubt - > Referring to ehci spec 3.6, looks like the QH has a Device Address that gets > tracked in qh->hw_info1 field. > > Refer - > qh_make ( > ... > info1 |= usb_pipeendpoint (urb->pipe) << 8; > info1 |= usb_pipedevice (urb->pipe) << 0; > ... > qh->hw_info1 = cpu_to_hc32(ehci, info1); > ... > > Isn't the QH identifying the destination pipe by an Endpoint Number + Device > Address?
Yes, you are right and I was wrong. The EHCI controller uses the device address field in the QH to store the value for the ADDR field of Token packets (see section 8.3 and 8.4 in the USB 2.0 spec). Alan Stern - To unsubscribe from this list: send the line "unsubscribe linux-usb" in the body of a message to [EMAIL PROTECTED] More majordomo info at http://vger.kernel.org/majordomo-info.html
