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--- linux:udev [2016/04/06 12:07]
niziak created
+++ linux:udev [2023/12/13 16:31] (current)
niziak
@@ Line 1: / Line 1: @@
-=== Debug ===
+==== udevadm ====
+=== reloading rules ===
+<code bash>udevadm control --reload-rules</code>
+<code bash>udevadm control --reload-rules && udevadm trigger</code>
+=== Testing rules ===
+<code bash>udevadm test /sys/class/tty/ttyACM0</code>
+NOTE: This program is for debugging only, it does not run any program specified by a RUN key. It may show incorrect results, because some values may be different, or not available at a simulation run.
+==== Getting info ====
+<code bash>
+udevadm info --attribute-walk --path=/sys/class/tty/ttyACM0
+udevadm info --attribute-walk --name=/dev/ttyUSB0
+</code>
+=== Get Telit modem serial number ===
+<code bash>
+udevadm info -q property -n /dev/ttyACM1 | grep ID_SERIAL_SHORT
+ID_SERIAL_SHORT=356136070718830
+</code>
+==== Debug ====
 <file | /etc/udev/udev.conf>
 udev_log="debug"
 </file>
+<code bash>
+udevadm control --log-priority=debug
+</code>
+==== Rules ====
+=== Order ===
+>Files should be named xx-descriptive-name.rules, the xx should be chosen first according to the following sequence points:
+>
+> < 60  most user rules; if you want to prevent an assignment being overriden by default rules, use the := operator.
+>
+>these cannot access persistent information such as that from vol_id
+>
+>< 70  rules that run helpers such as vol_id to populate the udev db
+>
+>< 90  rules that run other programs (often using information in the udev db)
+>
+> >=90  rules that should run last
+==== Executing commands ====
+Triggering commands should be done using RUN, because it is executed after all systemd actions.
+<code>
+SUBSYSTEM=="power_supply", ENV{POWER_SUPPLY_ONLINE}=="0", RUN+="/usr/bin/true"
+SUBSYSTEM=="power_supply", ENV{POWER_SUPPLY_ONLINE}=="1", RUN+="/usr/bin/true"
+</code>
+**RUN vs PROGRAM**
+PROGRAM is used to return device name, e.g. to return name for symlink. It is called during device setup, so it is not good place to execute external tools.
+<code>
+ACTION=="add", DRIVERS=="usb", ATTRS{manufacturer}=="Telit", ATTRS{idVendor}=="1bc7", ATTRS{idProduct}=="0021", PROGRAM="/bin/sh -c '/bin/echo -e {\\042imei\\042:\\042%s{serial}\\042} > /etc
+/imei.json'"
+</code>
+=== Shell ENV ===
+<code bash>
+ID_BUS=usb
+DEVNAME=/dev/ttyACM0
+ID_VENDOR_FROM_DATABASE=Telit Wireless Solutions
+ACTION=add
+ID_SERIAL_SHORT=356611070046259
+ID_USB_DRIVER=cdc_acm
+ID_TYPE=generic
+MAJOR=166
+DEVPATH=/devices/platform/ocp/47400000.usb/47401c00.usb/musb-hdrc.0.auto/usb1/1-1/1-1:1.0/tty/ttyACM0
+ID_MODEL_ENC=FIH7160
+ID_USB_INTERFACES=:020201:0a0000:020d00:0a0001:
+ID_MODEL=FIH7160
+DEVLINKS=/dev/serial/by-path/platform-musb-hdrc.0.auto-usb-0:1:1.0 /dev/serial/by-id/usb-Telit_FIH7160_356611070046259-if00
+ID_SERIAL=Telit_FIH7160_356611070046259
+SUBSYSTEM=tty
+ID_MODEL_ID=0036
+MINOR=0
+ID_PATH=platform-musb-hdrc.0.auto-usb-0:1:1.0
+ID_MODEL_FROM_DATABASE=LE910 V2
+ID_VENDOR_ENC=Telit
+ID_PATH_TAG=platform-musb-hdrc_0_auto-usb-0_1_1_0
+ID_VENDOR=Telit
+ID_USB_INTERFACE_NUM=00
+ID_VENDOR_ID=1bc7
+ID_REVISION=1730
+</code>
+=== Creating device symlinks ===
+<code>
+SUBSYSTEM=="input", KERNEL=="event[0-9]*", ENV{ID_INPUT_TOUCHSCREEN}=="1", ATTRS{name}=="edt-ft53*", SYMLINK+="input/touchscreen", OPTIONS+="link_priority=100"
+SUBSYSTEM=="input", KERNEL=="event[0-9]*", ENV{ID_INPUT_TOUCHSCREEN}=="1", ATTRS{name}=="ti-tsc",    SYMLINK+="input/touchscreen", OPTIONS+="link_priority=0"
+</code>
+''link_priority'': higher has higher priority
+Define symlink name in device tree (add property ''symlink'') i.e:
+<code>
+&pwm4 {
+	pinctrl-names = "default";
+	pinctrl-0 = <&pinctrl_pwm4>;
+	status = "okay";
+	symlink = "buzzer";
+};
+</code>
+<code>
+ATTR{device/of_node/symlink}!="", ENV{DEVNAME}!="", SYMLINK+="%s{device/of_node/symlink}"
+</code>
+See:
+  - [[https://github.com/mvduin/py-uio/blob/master/dts/pwmss2.dtsi#L122|pwmss2.dtsi]]
+  - [[https://github.com/mvduin/py-uio/blob/master/etc/udev/rules.d/10-of-symlink.rules|10-of-symlink.rules]]
+  - [[https://github.com/mvduin/py-uio/blob/master/dts/pwmss2.dtsi|pwmss2.dtsi]]
+=== Triggering systemd ===
+<code>
+SUBSYSTEM=="power_supply", ENV{POWER_SUPPLY_ONLINE}=="0", TAG+="systemd", ENV{SYSTEMD_WANTS}="powersaving.service"
+SUBSYSTEM=="power_supply", ENV{POWER_SUPPLY_ONLINE}=="1", TAG+="systemd", ENV{SYSTEMD_WANTS}="powersaving.service"
+SUBSYSTEM=="printer", TAG+="systemd", ENV{SYSTEMD_WANTS}="printer.target"
+</code>
+More info about systemd interactions: [[https://www.freedesktop.org/software/systemd/man/latest/systemd.device.html|systemd.device — Device unit configuration]]
+=== Prevent ModemManager ===
+<file | /etc/udev/rules.d/99-nomm.rules>
+ATTRS{idVendor}=="0451" ATTR{idProduct}=="bef3", ENV{ID_MM_DEVICE_IGNORE}="1"
+</file>

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