Hi Bjorn,

Yes. It was a TYPO. It should be ttyACM0, but not ttyAMC0. After changing to ttyACM0, it is working fine without any issues. Thanks.

As you said, yes, if we assign ttyACM*, then it works fine even if we insert our device later, after inserting other ttyACM devices, also. If we do not use * then it won't work if we insert our device after inserting other ttyACM devices.

My issue was resolved by changing the KERNEL=="ttyACM0" instead of KERNEL=="ttyAMC0". This is a simple TYPO and my overlooking while reading the rules.

Anyhow, I have changed the rule as shown below.

KERNEL=="ttyACM*", SUBSYSTEM=="tty", ATTRS{serial}=="__0X00124B000148CC78", SYMLINK+="mydev"

Then, all issues were resolved. It works fine irrespective of the device insertion, too.

Thank you all.

Regards,

Srinivas.

On Wed, Mar 5, 2014 at 4:29 PM, Bjørn Mork <bjorn@mork.no> wrote:

Srinivas Ganji <srinivasganji.kernel@gmail.com> writes:

> I have created a file, named 11-ttyACM.rules, under /etc/udev/rules.d
> directory. The contents of the file as follows.
> KERNEL=="ttyAMC0", SUBSYSTEM=="tty", ATTRS{serial}=="__0X00124B000148CC78",
> SYMLINK+="mydev"

So this rule will create a symlink from /dev/mydev -> /dev/ttyAMC0 if
all these conditions are met:

a) KERNEL=="ttyAMC0"
b) SUBSYSTEM=="tty"
c) ATTRS{serial}=="__0X00124B000148CC78"

I believe the a) condition is not exactly what you want. Firstly, the
spelling makes it likely to never match...

Secondly, even if you correct it to ACM, you really want this rule to
match regardless of which ttyACMx device is assigned. That way you can
ignore the device name and use the static /dev/mydev symlink.

So you'd want to do something like this instead:

KERNEL=="ttyACM*", SUBSYSTEM=="tty", ATTRS{serial}=="__0X00124B000148CC78", SYMLINK+="mydev"

> I got the above information from the following command
> udevadm info -q all -n /dev/ttyACM0 --attribute-walk
>
> This is what I did. But, no luck. If I insert a different serial numbered
> device, then it is assigning ttyACM0 to that device.

Yes. There is nothing in the rule controlling which name the kernel
assigns. You cannot change this in any case. It's already decided at
the point where the udev rule runs.

Bjørn