Re: attaching ugen(4) on multi interface USB devices

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To: ticso@cicely.de
Date: Thu, 07 Oct 2004 16:22:12 +0300

Bernd Walter writes:

> On Wed, Oct 06, 2004 at 03:30:05PM +0300, Niki Denev wrote:
>>
>> Hello everyone!,
>>
>> The last 1-2 days i've been trying to make some userspace OBEX utilities to
>> work with a USB based Nokia GSM phone and doing this i discovered something
>> that confuses me a little:
>> The phone in question is Nokia 6230 and it has an USB interface.
>> The phone has 11 interface descriptors,
>> 2 of them are used for the Modem and CM over data.
>> Judging from the windows drivers it seems that four of the other interfaces
>> are OBEX compatible.
>> But if i kldload umodem and plug the phone it detects only one ucom(4).
>> and if i plug the phone without any u* modules loaded the kernel attaches
>> ugen0 only.
>> >From what i understand it attaches the ugen0 using the info in the first
>> interface descriptor in the device.
>> Wouldn't it be more usefull for the kernel to attach ugen for every unknown
>> interface in a device.
>> For example when attaching the phone with umodem loaded, i will get
>> the ucom(4) device and the other unrecognised interfaces will show up as
>> ugens ?
>> What do you think about that?
>
> ugen attaches to the whole device and supporting all interfaces in one
> driver instance.

thanks, i saw this in the ugen(4) manpage. it seems that i haven't noticed
it before :(

> If you already an interface driver atatched then ugen fails to attach
> the whole device.

well, i think that this can be a problem sometimes.
actually i don't need kernel driver for obex devices, because everyting can
and will be probably better done in the userland via ugen.
but this means that the phone modem and obex interfaces can't be used
together.
why not having a ugen(4) for every USB device? even it is supported?
it probably won't harm anyone, but will make possible accessing parts of
the device that are otherwise hidden.

> 11 interface descriptors sounds unlikely to be correct - it's more
> likely that some of them are alternative configurations and a device
> or interface can only be in a single configuration at a given time.
> You can switch between alternative configurations via ugen.
>

It seems that this is the way that the CDC WMC (wireless mobile
communication) devices are made.
At least that is what i understand when reading some of the specifications
published at usb.org

> I don't know about OBEX, but why don't you just create an interface
> class driver that attaches to OBEX interfaces - writing USB drivers is
> not very difficult if you know USB and a few kernel basics.
>

I've done some testing in this area and i've made a driver based on
ucom/umodem that attaches to OBEX devices. (only attaches at the moment).
And here i discovered that usbdevs can't show more than 4 interfaces on USB
device. I tracked down this to USB_MAX_DEVNAMES=4.
Is there a reason for this to be set this low?

>> P.S.: anyone know some good way to list the attached usb devices beyond
>> usbdevs?
>> It seems that the information that can be gathered from usbdevs is very
>> limited. For example 'lsusb' in linux can show much more info. What do you
>> think about that too?
>
> I like usbctl from NetBSDs usbutils.
> An older port draft is available under:
> http://www.cosmo-project.de/~bernd/usbutil.tgz
> It will also show you the interface configurations with all
> alternatives.

usbctl and friends are nice! :)
i would love to see them in freebsd by default :)

P.S.:yesterday i have managed to panic my 6.0-current kernel
with usbctl, but i'm not sure if this is related to changes that i have
done.
i will cvsup to clean any problems in my source/rebuild and then report if
there are problems.

>
> --
> B.Walter BWCT http://www.bwct.de
> bernd@bwct.de info@bwct.de
>

thanks!

--niki

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