Hi, Alan, > -----Original Message----- > From: Alan Stern [mailto:stern@xxxxxxxxxxxxxxxxxxx] > Sent: Saturday, July 25, 2009 8:31 AM > To: Julie Zhu > Cc: USB list > Subject: Re: Question on clear_tt_buffer for not TDI but with built-in TT > > On Fri, 24 Jul 2009, Julie Zhu wrote: > > > Hello, > > > > I have a question about the interface for clear_tt_buffer that has been > > added into 2.6.31-rc3. We are working with an EHCI host controller that > > has a transaction translator built-in. Therefore, it is naturally TDI > > (by ehci_is_TDI() check for has_tt). In the handling of clear_tt_buffer, > > if it is TDI, then clear_tt_buffer control message is not sent out. > > However, we do not have the way that is commented in ehci-q.c: > > > > /* REVISIT ARC-derived cores don't clear the root > > * hub TT buffer in this way... > > */ > > > > We actually need the clear_tt_buffer control message sent to the > > built-in transaction translator. What should we do? > > This is an important issue. It turns out that some TDI-type designs > require the built-in TT to be notified when the buffer has to be > cleared and some don't, or at least, they don't provide any way to send > the notification -- I don't understand why not. I don't know what the > best approach will be. > In our case, we do provide a way to send the notification, just as the way the USB spec says, through a control message of CLEAR_TT_BUFFER. How can we send this message out, even we have built-in TT? Do we need a special flag? Thanks, Julie. > > I believe the clear_tt_buffer control message is to notify the > > transaction translator about software-side cancellation/failure? I know > > we can handle hardware-side failures just fine without the need of > > clear_tt_buffer control message. > > Yes, that is correct. > > Alan Stern > This email and any attachments are intended for the sole use of the named recipient(s) and contain(s) confidential information that may be proprietary, privileged or copyrighted under applicable law. If you are not the intended recipient, do not read, copy, or forward this email message or any attachments. Delete this email message and any attachments immediately. -- 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
