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linux:udev [2016/04/06 12:07] – created niziaklinux:udev [2023/12/13 16:31] (current) – niziak
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-=== 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> <file | /etc/udev/udev.conf>
 udev_log="debug" udev_log="debug"
 </file> </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>
 +