On Thu, Oct 10, 2024 at 8:24 AM Daniel Spannbauer <ds@xxxxxxxx> wrote:
Am 09.10.2024 um 20:55 schrieb Andrei Borzenkov:
> 09.10.2024 17:02, Daniel Spannbauer wrote:
>> Hello,
>>
>>
>> thanks for the response.
>>
>> My rule is in "55-my-rules.rules"
>>
>
> For SUBSYSTEM=="tty" the usb_id is called in 60-serial.rules.
Thats the trick, thanks.
I moved my rules to 98-.... and this line works:
SUBSYSTEM=="tty", KERNEL=="ttyACM[0-9]*",
ENV{ID_USB_INTERFACE_NUM}=="02", ATTRS{idVendor}=="1dfb",
ATTRS{idProduct}=="0010", SYMLINK+="2a"
It also works with SUBSYSTEMS=="usb".
But the following still doesn't work:
SUBSYSTEM=="tty", KERNEL=="ttyACM[0-9]*", ATTRS{bInterfaceNumber}=="02",
ATTRS{idVendor}=="1dfb", ATTRS{idProduct}=="0010", SYMLINK+="2a
I suspect this is because idVendor and bInterfaceNumber are from different levels of the hierarchy – one belongs to the USB device parent, the other belongs to its usb_interface child.
ATTRS is "sticky" – it only does the upward search *once* per rule, so e.g. after it finds bInterfaceNumber on the 'usb_interface' level, it will expect all other attributes to be there as well. I think the same applies to ENVS.
So if you need to gather sysfs attributes from multiple levels, you probably need to use separate rules to copy them into ENV one-by-one, either using ATTRS directly or using IMPORT{parent} or something.
I suppose that is why most of the information is already being duplicated as ENV by the stock rules to begin with – because ENV is easier to import from multiple layers of parents.
And how can I find out, which value comes with which rules so I can set
my rules at the right time?
I grepped my ~/src/systemd/src for "ID_USB_INTERFACE_NUM" and saw it defined in udev-builtin-usb_id.c, then I grepped /lib/udev/rules.d for "usb_id". Generally safest to place your rules no earlier than 80-*, I guess.
--
Mantas Mikulėnas
