Improve serial symlink (/dev/serial<n>) creation #76
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MichaIng
reviewed
Jun 19, 2023
etc.armhf/udev/rules.d/99-com.rules
Outdated
| fi \ | ||
| KERNEL=="ttyAMA[0-9]*|ttyS[0-9]*", PROGRAM="/bin/sh -c '\ | ||
| ALIASES=/proc/device-tree/aliases; \ | ||
| TTYNODE=`readlink /sys/class/tty/%k/device/of_node | sed 's/base/:/' | cut -d: -f2`; \ |
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What about using modern command substitution syntax (same in other cases below)?
Suggested change
| TTYNODE=`readlink /sys/class/tty/%k/device/of_node | sed 's/base/:/' | cut -d: -f2`; \ | |
| TTYNODE=$$(readlink /sys/class/tty/%k/device/of_node | sed 's/base/:/' | cut -d: -f2); \ |
Rationale: https://www.shellcheck.net/wiki/SC2006
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Have you tried that in a udev rule?
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Ah right, the dollar signs need to be escaped with $$. Just tested on RPi Zero W:
root@Amizero:~# cat /etc/udev/rules.d/test.rules
KERNEL=="wlan0", ACTION=="add", RUN+="/bin/sh -c 'echo $$(echo success) > /root/test'"
root@Amizero:~# cat /root/test
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I'm guessing you haven't, otherwise you'd know it's a bad idea.
Rationale:
Jun 19 14:47:39 raspberrypi systemd-udevd[189]: /etc/udev/rules.d/99-com.rules:35 Invalid value "/bin/sh -c 'ALIASES=/proc/device-tree/aliases; TTYNODE=$(readlink /sys/class/tty/%k/device/of_node | sed 's/base/:/' | cut -d: -f2); if [ -e $$ALIASES/bluetooth ] && [ $$TTYNODE/bluetooth = `strings $$ALIASES/bluetooth` ]; then echo 1; elif [ -e $$ALIASES/console ]; then if [ $$TTYNODE = `strings $$ALIASES/console` ]; then echo 0;else exit 1; fi elif [ $$TTYNODE = `strings $$ALIASES/serial0` ]; then echo 0; elif [ $$TTYNODE = `strings $$ALIASES/serial1` ]; then echo 1; else exit 1; fi '" for PROGRAM (char 56: invalid substitution type), ignoring.
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See my last post: Double $$ needed just like for variable calls.
MichaIng
reviewed
Jun 19, 2023
etc.armhf/udev/rules.d/99-com.rules
Outdated
| KERNEL=="ttyAMA[0-9]*|ttyS[0-9]*", PROGRAM="/bin/sh -c '\ | ||
| ALIASES=/proc/device-tree/aliases; \ | ||
| TTYNODE=$$(readlink /sys/class/tty/%k/device/of_node | sed 's/base/:/' | cut -d: -f2); \ | ||
| if [ -e $$ALIASES/bluetooth ] && [ $$TTYNODE/bluetooth = `strings $$ALIASES/bluetooth` ]; then \ |
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One last:
Suggested change
| if [ -e $$ALIASES/bluetooth ] && [ $$TTYNODE/bluetooth = `strings $$ALIASES/bluetooth` ]; then \ | |
| if [ -e $$ALIASES/bluetooth ] && [ $$TTYNODE/bluetooth = $$(strings $$ALIASES/bluetooth) ]; then \ |
A tiny thing, I know. I just can't hold myself when seeing backticks in shell code, aiming for best practice coding 🙂.
The kernel change that sets UART indexes based on Device Tree aliases
gives predictable UART /dev/tty* names but has the potential to break
our downstream use for determining which UART is the console
("serial0") and which is for Blueooth ("serial1"). Instead we use the
"console" and "bluetooth" aliases respectively.
As a bonus, the improved console matching (based on /sys/class/tty
entries) also allows us to handle all UARTs with one rule.
MichaIng
added a commit
to MichaIng/DietPi
that referenced
this pull request
Jun 21, 2023
- Raspberry Pi | Update serial console udev rules: RPi-Distro/raspberrypi-sys-mods#76
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The kernel change that sets UART indexes based on Device Tree aliases gives predictable UART /dev/tty* names but has the potential to break our downstream use for determining which UART is the console ("serial0") and which is for Blueooth ("serial1"). Instead we use the "console" and "bluetooth" aliases respectively.
As a bonus, the improved console matching (based on /sys/class/tty entries) also allows us to handle all UARTs with one rule.