On Mon, 9 Feb 2004, Frank Barknecht wrote:[snip]
But the Quattro has configurations, where it tells the kernel: "I got
two alt settings, dude." The kernel and all applications now know that
those are [0,1], because that's what the standard says. But in the
case of the Quattro they are [0,4]! Every configuration of the Quattro
is broken in this way. Some say, they would have 4 settings and those
are [0,1,3,4]! This has nothing to do with the lenghth of the array but
with the allowed values it can included.
However the uncomfortable thing is that Windows does seem to be able toNo, it's more likely that the Quattro driver for windows was written by the hardware manufacturers wth a casual disregard for (or misunderstandng of) the USB specs.
handle this. and the Standard that the windows USB driver was written to
was surely the same one as the Linux one. Thus this card should also
break in windows ( which should make M-audion sit up and take notice,
even if they regard Linux with distain).
It's immaterial which is worse. An off-by-one error could be entirely harmless in this context or it could be catastropic. The inability to acces the wrongly numbered alt device could be merely a question of "fixing" the Quattro in it's USB driver or it could be necessary to break the whole USB subsystem to support this one device. Someone with the time (and preferably Quattro) would have to look into exaclty what goes on in the driver.I don't know the USB system in the kernel, so I'm guessing a bit here: The kernel checks this early on and rejects this device, because it doesn't know what might break later on in code paths that rely on the alt settings being correctly identified. Such path aren't hard to think of, they could for example be loops like this (Python-pseudocode):
numSettings = kernel.getAltSettings() # numSetting now is an int like 2
for setting in range(0,numSettings):
doSomethingWith(setting)
That would not be as bad as driver[kernel.getSettingNumber(3)]
jch
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