UART and USB ttys together ports not working
Florian Eckert
fe at dev.tdt.de
Wed Dec 11 12:34:31 UTC 2024
Hello Aleksander
On 2024-12-11 13:18, Aleksander Morgado wrote:
>>> ....
>>> Also, please note, the kernel does not guarantee that the ttyUSB
>> and
>>> ttyAMA ports are always named in the same way, so using udev rules
>>> like that is error-prone. A much better approach would be to bind
>> the
>>> udev rules to specific sysfs paths, e.g.
>>> DEVPATH=="/devices/pci0000:00/0000:00:1d.0/usb4/4-1/4-1.5/4-1.5.5"
>>
>> Only a note:
>> I have noticed that the path is no longer fixed with newer kernels.
>> The problem is the `usb<port-number>` in your example `usb4`. This
>> is
>> random and can be different for each boot, since probing of the usb
>> root hubs are now done asynchronous during but. I have noticed this,
>> on my APU3 board which is running the kernel version 6.6.xxx
>> (owrt-24.10).
>
> Oh wow, if this is true, I know many things that will break. Is this a
> recent change, and if so, could you point me to the relevant kernel
> commit?
We already discussed this on the OpenWrt-Mailinglist a few month ago
[1].
The problem arise during the rebase of OpenWrt master to the new
linux kernel '6.6' on my x86/64 APU3 board.
This commit [2] changed the behavior during probe for my usb hub on the
APU3.
I discovered the problem in connection with the ModemManager so that I
can
use alias names for the modem on my system. I didn't think it would
affect
the ModemManager directly!
Best regards
Florian
[1]
https://lists.openwrt.org/pipermail/openwrt-devel/2024-July/043048.html
[2]
https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/commit/?id=69a1c9a9b273271f2a2674bcc117336a9bb0a4b4
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