USB serial device naming

[Alexandr Rybalko]

Hi,

On Wed, 5 May 2010 10:46:30 +0200
Milan Obuch <freebsd-usb at dino.sk> wrote:

>> 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.

I think better way is use device connection path in name.
User know to which port of hub they attach device, so name like /dev/cuaU.h0p1.h2p3 (root hub 0, port 1, hub 2, port 3 ) have all
information user need and this name not changing between reboot`s.
May by we have way make naming more simple, but we really need path somewhere in device name.

>> 
>> > 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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-- 
Alexandr Rybalko <ray at dlink.ua> 
aka Alex RAY <ray at ddteam.net>