On 10/31/2013 02:03 AM, rran...@ihug.com.au wrote:
I have run into an issue which seems to call into question the udev
paradigm for USB devices. In my case it has ramifications in
ModemManager and gpsd packages, but I see it as a fundamental problem
with udev which is in all current versions of Fedora.
My USB GPS is a BU-353 which uses a pl2303 USB-Serial Controller
(idVendor=067b, idProduct=2303). However, bugzilla report 878737
indicates this same interface chip is used on other devices such as
RS232-USB adapters.
If the device is a GPS you do not want ModemManager run on it
(bugzilla 1023234) but you do want gpsctl to tell gpsd about it when
it is plugged in. If it is a RS232 adapter the opposite is true
(bugzilla 878737). Note that it is reported that the DU-353 can be
bricked if the wrong thing is written to it.
After looking at the lsusb -v output for my BU-353 and the output for
RS232 devices reported on the net, I do not see any way to distinguish
between the two different types of devices that udev could use to tell
them apart.
Unless I am missing something this seems like a fatal flaw in the udev
paradigm.
As the others have said, there's no way to determine what's sitting
behind those serial controllers so it's not a problem with udev but with
the hardware it has to handle. The default udev setting is, or at least
used to be, designed for the most common case, which turns out wrong for
you. No matter what udev does, someone is not going to get their device
auto-configured, so the right choice is to handle the most common case.
Now, it's possible that modems aren't just used much any more, so that
requiring manual scan would make sense, and udev makes it possible.
By the way, it seems to me that on a computer with no modems, one should
simply uninistal ModemManager:
yum erase ModemManager
--
devel mailing list
devel@lists.fedoraproject.org
https://admin.fedoraproject.org/mailman/listinfo/devel
Fedora Code of Conduct: http://fedoraproject.org/code-of-conduct