Hi Matt, Do you work for the government? Replacing a $1 hub chip with a $1000 computer? :)
More below: >>On Mon, 11 Dec 2006, Matt wrote: >> >> > Hi, >> > >> > I'm wondering if it's feasible to implement a gadget driver that turns >>a >> > Linux system into a hub. The hub specification in the usb spec, which >>I >> > admit to not reading, is fairly hefty and makes me think there's >> > probably a fair bit more to it then just proxying data to an outbound >> > port or one of the gadget developers would have done it already. This >> > is something I'd like to try to do so any thoughts or comments would be >> > much appreciated. Where would one start? Cheers, >> >>It isn't possible. >> Alan is right, it is not possible. The main reason is the required timings. Hubs have very strict requirements in terms of the number of bit times things can be delayed passing through a hub. This is so 5 hubs can be connected together in a line and the ack/nak/stall following an EOP can still meet the required timing. >>Among other problems, a full-speed hub has to be able to handle both >>low-speed and full-speed devices attached to its downstream ports, in >>spite of the fact that the upstream port is full-speed. If a low-speed >>device was attached to a downstream port then the upstream port would >>receive data at low speed, and would not be able to understand that data >>or forward it to the downstream port. >> This is not true. Alan, you are confusing High speed with Full speed. All full and low speed transactions appear on the downstream ports of all full speed hubs. Upstream only goes up through the chain directly to the root - what I mean is hubs don't echo downstream data that is going upstream. But the upstream data is still sent at low speed, if that is what the device sends. A PRE pid is sent to tell full speed devices that a low speed packet is coming. This is mainly so the hubs can direct the low speed traffic downstream. It is true that a low speed device should never see a full speed bit stream. Regards, Steve _________________________________________________________________ Talk now to your Hotmail contacts with Windows Live Messenger. http://clk.atdmt.com/MSN/go/msnnkwme0020000001msn/direct/01/?href=http://get.live.com/messenger/overview ------------------------------------------------------------------------- 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 _______________________________________________ linux-usb-devel@lists.sourceforge.net To unsubscribe, use the last form field at: https://lists.sourceforge.net/lists/listinfo/linux-usb-devel
