Re: patch usb-iowarrior.patch added to gregkh-2.6 tree
Alan Stern <[email protected]>
| Newsgroups | gmane.linux.usb.devel |
|---|---|
| Message-ID | <[email protected]> |
On Tue, 20 Feb 2007, Guido Körber wrote: > OK, I am starting to understand where that comes from. > > First of all USB does not allow to send two reports in a single > transfer. That's right. Section 8.4 of the USB HID specification explicitly says: Only one report is allowed in a single USB transfer. However vendors do not always obey the specification. > The effect that was described in the forum is likely something that > happens in the buffers of the host controller. Since he writes that > he had to ignore interrupts for a while to see it this situation > likely only arises if another transfer arrives before the last one > has been serviced. They would still be presented as two separate transfers. The host controller drivers are very careful about keeping different transfers apart. > I would suspect that there is some problem in the host controller > driver that concatenates reports under certain conditions. No. In fact, the driver in question had requested a single packet transfer. Much more likely is that the delay caused by ignoring interrupts gave the keyboard time to accumulate more events, and the keyboard combined the reports into a single packet. Without seeing the actual data, though, we can only speculate about the real cause. Alan Stern ------------------------------------------------------------------------- Take Surveys. Earn Cash. Influence the Future of IT Join SourceForge.net's Techsay panel and you'll get the chance to share your opinions on IT & business topics through brief surveys-and earn cash http://www.techsay.com/default.php?page=join.php&p=sourceforge&CID=DEVDEV _______________________________________________ [email protected] To unsubscribe, use the last form field at: https://lists.sourceforge.net/lists/listinfo/linux-usb-devel