When I plug in a pl2303-based usb serial device, the device is
supposed to appear as /dev/tts/USB0 (character device 188, 0).
However, under kernels that I have tried from 2.6.20-git3 through
2.6.21-rc2-git1, /dev/tts/USB<some-random-number> is created, and
attempting to open that file returns a "no such device" error. I have
not seen that random number exceed 256, by the way. Doing "mknod
/dev/tts/USB0 c 188 0" and then opening that file resulted kernel oops
on the one kernel version on which I tried it (I think around
2.6.20-git11).
I remember seeing almost exactly these symptoms a few years
ago.
I imagine that this is some kind of tty unit number not be
initialized, so I guess it's worth mentioning that all of the USB
things in my configuration are built as loadable modules.
Here is a list of the kernels that I have tried, and the results:
2.6.20 OK
2.6.20-git1 OK
2.6.20-git2 OK
2.6.20-git3 fail
2.6.20-git7 fail
2.6.20-git11 fail
2.6.21-rc1 fail
2.6.21-rc2-git1 fail
There are moderate to substantial changes to
drivers/usb/serial/usb-serial.c in 2.6.20-git3, and only a couple of
innocuous looking lines changed in linux/usb/serial/. I will be
investigating the usb-serial.c changes, if nobody beats me to a fix,
although the time that I can put into this may be rather limited over
the next few days.
Adam Richter
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