Create udev rule for USB device with multiple virtual ports

[lilipop2513]

Hello Linux Community !

In my embedded project, I came across working with multiple USB devices. So, to avoid checking each time the new port of each device and setting that in my code, I decided to use udev rules to have a unique access to each device.

However, in that process, one device is causing a problem since it has 2 virtual ports (config + data). If I do a standard udev rule for it, I get one access created to the config port only.

Any clues on how to set udev rules for device with 2 virtual ports ?

Thanks in advance,
Lilia

 

[wizardfromoz]

G'day Lilia and welcome to linux.org

This is beyond my knowledge but by my mentioning the following Members -

@JasKinasis , @dos2unix , @osprey , @f33dm3bits (and there are likely others) I have brought this Thread to their attention.

Make allowance for timezone differences.

Once one of those folks lets me know, I may move this Thread to our Command Line subforum, if it involves, as I suspect, writing udev rules.

Good luck

Chris Turner
wizardfromoz

 

[osprey]

What comes to mind as an initial thought is that it's quite possible to have multiple rules for the same device, so, for example, if you could create a rule each for the two components (the 2 virtual ports), they could be in files with numbers close to each other (e.g. 70-<name>.rules, and 71-<name2>.rules) to determine the order of execution, or, one can have multiple rules in the same file with the rules separated by new lines with each run on a single line. I suppose it's going to depend on whether udevadm identifies the two components. Just thinking.

 

[lilipop2513]

What comes to mind as an initial thought is that it's quite possible to have multiple rules for the same device, so, for example, if you could create a rule each for the two components (the 2 virtual ports), they could be in files with numbers close to each other (e.g. 70-<name>.rules, and 71-<name2>.rules) to determine the order of execution, or, one can have multiple rules in the same file with the rules separated by new lines with each run on a single line. I suppose it's going to depend on whether udevadm identifies the two components. Just thinking.

Hey, thanks for the reply.

It is actually one component with 2 virtual ports, means the two has same vendor id, product id and so on. I don't seem to find something that could make the difference between the two.

If you have any ideas, tell me please.

 

[dos2unix]

Even though it's the same device, aren't the ports identified uniquely?

 

[lilipop2513]

Even though it's the same device, aren't the ports identified uniquely?

Yes the ports are identified uniquely in the /dev directory (exp : ttyUSB0 & ttyUSB1).

Let me reput my question in a better way :

1- Here's a look at what my first tested rule looked like :

SUBSYSTEM=="tty", SUBSYSTEMS=="usb", ATTRS{idVendor}=="10c4", ATTRS{idProduct}=="ea70", SYMLINK+="ttyDevice"

I thought that since the device has 2 virtual ports, it would create 2 symlinks but when it takes effect it only gives one symlink that neither allows access to the config nor to the data (basically does nothing).

2- Now, to create my rule, I use the following command for each port (USB0 & USB1) :

$udevadm info --attribute-walk /dev/ttyUSB0

However the result gives same details for both ports (Vendor Id, Product Id... everything). The only and unique difference I seem to find is the following :
USB0 : ATTRS{interface}=="Enhanced Com Port"
USB1 : ATTRS{interface}=="Standard Com Port"

If I test making two rules with this slight difference :

SUBSYSTEM=="tty", SUBSYSTEMS=="usb", ATTRS{interface}=="Standard Com Port", ATTRS{idVendor}=="10c4", ATTRS{idProduct}=="ea70", SYMLINK+="ttyDeviceStandard"
SUBSYSTEM=="tty", SUBSYSTEMS=="usb", ATTRS{interface}=="Enhanced Com Port", ATTRS{idVendor}=="10c4", ATTRS{idProduct}=="ea70", SYMLINK+="ttyDeviceEnhanced"

It does not work.

PS : I make sure to reload the rules each time with the command below and a reboot

sudo udevadm control --reload-rules && udevadm trigger

So to sum it up, my question is :
what's the thing that I can add in the rule of each virtual port to distinguish between them and make sure each has a proper symlink for it ?
Or is there a better way to proceed, am I doing things wrong ?
If you have any clues please share them
Thank you !

 

[Dense]

Same question here. Teensy set up for 3 serial ports appears in /dev/ as ttyACM(n), ttyACM(n+1), ttyACM(n+2) Where n depends on previous devices loaded or not. How to make udev rules to assign 3 symlinks where all device attributes are the same?