USB serial device naming
Milan Obuch
freebsd-usb at dino.sk
Wed May 5 08:44:54 UTC 2010
On Wednesday 05 May 2010 09:52:15 Hans Petter Selasky wrote:
> Hi,
>
> Maybe you can make PR on the issue and assign it to USB. Currently there is
> no way of knowing which /dev/cuaUXXX belongs to which USB device. Probably
> we can add the USB bus and address number as a part of the device
> coordinates. So that /dev/ugen1.1 only creates /dev/cuaU1.1.xxx entries.
> And then we can also remove the current unit number allocation structure I
> guess, if we use:
>
> /dev/cuaU1.1.<iface_number>.<optional_sub_modem_unit>
>
> The only problem is: Will we break any existing applications?
>
Well, yes, to some extent :) Problem with this naming convention is name
changes with every port change - that is, if you pull USB cable out and plug
it in another port. There was already some older thread about naming on
freebsd-usb list (end of April 2009). But if devd receives all necessary
informations in attach event, then it is possible to rewrite config files or
create symlink in /dev directory or something like this to handle this
situation.
> The second problem was that the USB attach event was generated before the
> modem was probed and the umodem and other modem drivers do not provide any
> information about their USB address in the pnpinfo. This can be fixed.
>
> Old pnpinfo:
>
> dev.ums.0.%pnpinfo: vendor=0x0 product=0x0 devclass=0x00 devsubclass=0x00
> sernum="" release=0x0200 intclass=0x03 intsubclass=0x01
>
> Suggested new pnpinfo (which is available from devd.conf I guess)
>
> dev.ums.0.%pnpinfo: vendor=0x0 product=0x0 devclass=0x00 devsubclass=0x00
> sernum="" release=0x0200 intclass=0x03 intsubclass=0x01 bus=1 addr=2
> ifaceidx=0
>
This would be good thing to do I think. Just a typo spot here - ums means USB
mouse driver, I think, but this idea is worth evaluating.
My sole concern is use somehow stable names for situations when more than one
serial port (serial USB cable, u3g modem etc) is attached so each device is
properly used in correct program.
Regards,
Milan
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