udev rule for matching USB class and subclass?

[Felipe Sateler]

On 10 October 2016 at 10:26, Petter Reinholdtsen <pere at hungry.com> wrote:
>
> Hi.
>
> I've been trying to figure out if it is possible to write a udev rule
> matching USB class and subclass, without any success so far.  My goal is
> to write a rule matching any smart card reader, instead of individual
> smart card readers.  But is it possible with udev?
>
> With AppStream / isenkram I can match it using the modaliases from the
> kernel.

I think so. There is the the ENV{MODALIAS} attribute that you can match on.

> The following oneliner will print the modalias for any smart
> card reader installed in the system:
>
>   for mod in $(cat $(find /sys/|grep modalias|grep usb)); do \
>      case "$mod" in usb:*ic0Bisc00ip*) echo $mod; esac; \
>   done
>
> But the scdaemon udev rule list individual vendor/product IDs instead of
> specifying class 0B and subclass 00.  It there any way around this?

I do not have any idea why upstream scdaemon would have chosen that
path. Perhaps the modalias can bring a false positive? I see that the
rules also sets a gnupg driver, perhaps the scdaemon supports other
smartcard readers not supported by the gnupg driver?

-- 

Saludos,
Felipe Sateler