On Thursday 03 November 2005 8:31 am, Alan Stern wrote: > On Thu, 3 Nov 2005, David Brownell wrote: > > > > When I do see syslog messages, they look like this: > > > > > > Nov 2 20:51:38 daydream kernel: usb 1-8: device descriptor read/64, > > > error -71 > > > Nov 2 20:51:38 daydream last message repeated 3 times > > > Nov 2 20:51:39 daydream kernel: usb 1-8: device not accepting address > > > 14, error -71 > > > Nov 2 20:51:39 daydream kernel: usb 1-8: device not accepting address > > > 15, error -71 > > > > This is early enumeration code. In fact, the read/64 stuff doesn't need > > to be done; there's only one ep0 maxpacket size possible for high (or low) > > speed devices. One person reported some success with a patch that bypasses > > the "guess the ep0 maxpacket" dance except for full speed (which is the only > > case where it's necessary) ... one theory is that since that dance forces > > devices into certain fault modes, either (a) devices don't always handle > > those fault modes correctly, or (b) Linux doesn't. So bypassing those > > fault modes could make them both happier. > > One way to test this theory is to use the undocumented > "old_scheme_first=y" parameter for the usbcore module.
Actually that doesn't get rid of the fault mode (short reads), it just moves it to a different place. Then there's the other fault mode, where if SET_ADDRESS fails it's not clear whether the address change actually took effect ... - Dave ------------------------------------------------------- SF.Net email is sponsored by: Tame your development challenges with Apache's Geronimo App Server. Download it for free - -and be entered to win a 42" plasma tv or your very own Sony(tm)PSP. Click here to play: http://sourceforge.net/geronimo.php _______________________________________________ [email protected] To unsubscribe, use the last form field at: https://lists.sourceforge.net/lists/listinfo/linux-usb-devel
