On Wed, 6 Oct 2010, gene heskett wrote: > Greetings all; > > I am having a heck of a time with my usb tree. The number of devices that > I have (about 18 when all are plugged in) exceed the available ports (10) > on my motherboard. So I've been playing with hubs. If I put a 4 port > powered hub on a mobo socket, and plug in the more distant stuff, it works > fairly well, but does require that I use 2 of the long extension cables to > reach some stuff in the basement, a printer, and a usb-ser adapter. > However, neither of my 7 port hubs (one an Alps, one a Staples, both usb2.0 > rated) can be substituted in this same location as the same extension cable > (with a 1 port hub for a booster built in) then returns either an error > -32, or an error -71 as seen in a tail of the log. > > I get the impression that part of this error is because the timeouts in the > usb drivers do not allow enough time for a distant hub, say 3 effective > repeaters or more out on a branch, to respond to the enumeration query. Devices are allowed 10 seconds to reply to enumeration requests. Since the delay time added by each hub in the chain is on the order of microseconds or less, I don't think this is the cause of your problem. More likely it's a signal strength or signal quality issue. > FWIW, I have looked through the usb docs in the kernel tree, currently > running 2.6.35.7, without encountering a list of error codes vs ERRNO > strings, so I have NDI what the -32 or -71 errors are actually telling me. The files you want are Documentation/usb/error-codes.txt and include/asm-generic/errno*.h. > Except for the 4 and 7 port hubs, everything else including the extension > cables are FTDI based, pl2303 stuff is verboten. > > Is there a single location in the usb driver(s) where this allowable delay > can be increased? Or perhaps multiplied by the number of repeaters in that > particular branch? No, these things are controlled entirely by the hardware. The operating system cannot affect them. Alan Stern -- 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
