On Wednesday, October 06, 2010 01:35:18 pm Alan Stern did opine: > 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. If you add in errno-base.h (to get them all) and assume the - sign, that's protocol and pipe. Both of which could be poor signals. Thanks Alan. I just spent an hour drilling more holes in the wall/floor here, so I could get those two long extension cables to a direct from the mobo port. The ports I used are on a breakout back panel slot, and add about 15" to the cable length, plus of course the big lump from the connector junctions at the slot filler. Neither one works, error -71. So, move those two to a powered hub which adds about 4 feet of cable from the hub to the port, and both are now working. So if the mobo ports have as much signal driver power as the 4 port hub, then its the extra 15" of cable from the mobo to the slot filler and the (low) impedance lumps at the slot filler sockets that are killing it. Damn if I do, and damned if I don't. I guess the upshot of this is that as an rf broadcast engineer, I have learned that the VSWR present on USB cables is in no way, properly terminated. It it was, then it should be somewhat like the scsi buss, whose original specs 35-40 years ago claimed to have a max cable length limit of 39 meters, if it was properly terminated on both ends to absorb the echos from 5ns signal edges. But between the engineers and the production floor was a bean counter who bought the cheapest +-20% parts he could buy, so we have had 35+ years of scsi having a reputation that not even sacrificing virgins would make it work reliably. Maybe it still has that rep, I haven't used it for a tape drive in yonks, vtapes on a hard drive are easily 50x more dependable and 100x faster to recover from. I have fixed a lot of scsi systems right, and without using up any hard to find virgins, made them truly bulletproof. Bean counters will be the death of anything they touch, could we start a bounty system on them? ;-) > > 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 Thanks Alan. -- Cheers, Gene "There are four boxes to be used in defense of liberty: soap, ballot, jury, and ammo. Please use in that order." -Ed Howdershelt (Author) You may get an opportunity for advancement today. Watch it! -- 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
