[RFC] Probing ttys by default

Sven Köhler sven.koehler at gmail.com
Fri Mar 21 04:47:08 PDT 2014

Am 21.03.2014 13:35, schrieb Aleksander Morgado:
> On Fri, Mar 21, 2014 at 11:37 AM, Sven Köhler <sven.koehler at gmail.com> wrote:
>> The kernel cdc_acm driver could expose whether the device seems to be a
>> modem. It knows, through the bmCapabilities field in the CDC Call
>> Management descriptor [1]. Another field that comes to mind is the
>> bInterfaceProtocol of the Interface Descriptor. For devices that don't
>> speak AT-commands it should be zero.
>> Then one can craft some general udev rule that grey- or blacklists
>> (what's the difference) all devices that don't seem to be a modem. If
>> there devices out there that erroneously report that they don't have
>> calling capabilities, then that those would have to be whitelisted.
>> I can confirm that for the UMTS card in my Laptop, lsusb explicitly
>> lists that it speaks the AT-commands protocol (bInterfaceProtocol=1) and
>> that it has call management (bmCapabilities=3 in the CDC Call Management
>> descriptor).
> Bjørn, Dan, do you guys think that this is something doable? Or,
> otherwise, do you have any other idea on how we can handle this
> better?

BTW: OS X had the same problem. They did something about it based on the
USB descriptors, according to this post:

Not sure what they did, which fields they used, etc.

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