]> git.ipfire.org Git - thirdparty/systemd.git/commit
udev: add option to trigger parent devices despite filters
authorFederico Giovanardi <federico.giovanardi@cnhind.com>
Thu, 17 Oct 2024 13:29:51 +0000 (15:29 +0200)
committerLennart Poettering <lennart@poettering.net>
Mon, 16 Dec 2024 14:43:52 +0000 (15:43 +0100)
commit7fd45eec37840036f6659fa15e73a9fd896d5613
tree8217a73cfcebb3360525825edb6d9d72213176f6
parenta0c314d6b04c0a20d566b15c759d18cdb2916c14
udev: add option to trigger parent devices despite filters

This commit add the `-i` option to `udevadm trigger` that force it to
match parent devices even if they're excluded from filters.
The rationale is that some embedded devices have a huge number of
platform devices ( ~ 4k for MX8 ) they are there because they're defined
in the device tree but there isn't any action or udev rules associated
with them.

So at boot a significant time is spend triggering and processing rules
for devices that don't produce any effect and we would like to filter
them by calling:

```
udevadm trigger --type=device --action=add -s block -s tty
```

instead of the normal

```
udevadm trigger --type=device --action=add
```

so we can use filter to filter out only subsystems for we we know that
we have rules in place that do something useful.

On the other side action / rules are not triggered until the parent is
triggered ( which is part of another subsystem), so the additional option
will allows udev to complete the coldplug with only the devices we care.

Example on iMX8:

.Without the new option
```
root@dev:~# udevadm trigger --dry-run  -s block --action=add -v
/sys/devices/platform/bus@5b000000/5b010000.mmc/mmc_host/mmc0/mmc0:0001/block/mmcblk0
/sys/devices/platform/bus@5b000000/5b010000.mmc/mmc_host/mmc0/mmc0:0001/block/mmcblk0/mmcblk0boot0
/sys/devices/platform/bus@5b000000/5b010000.mmc/mmc_host/mmc0/mmc0:0001/block/mmcblk0/mmcblk0boot1
/sys/devices/platform/bus@5b000000/5b010000.mmc/mmc_host/mmc0/mmc0:0001/block/mmcblk0/mmcblk0p1
/sys/devices/platform/bus@5b000000/5b010000.mmc/mmc_host/mmc0/mmc0:0001/block/mmcblk0/mmcblk0p2
/sys/devices/platform/bus@5b000000/5b010000.mmc/mmc_host/mmc0/mmc0:0001/block/mmcblk0/mmcblk0p3
/sys/devices/platform/bus@5b000000/5b010000.mmc/mmc_host/mmc0/mmc0:0001/block/mmcblk0/mmcblk0p4
```

.With the new option
```
root@dev:~# udevadm trigger --dry-run -i -s block --action=add -v
/sys/devices/platform
/sys/devices/platform/bus@5b000000
/sys/devices/platform/bus@5b000000/5b010000.mmc
/sys/devices/platform/bus@5b000000/5b010000.mmc/mmc_host/mmc0
/sys/devices/platform/bus@5b000000/5b010000.mmc/mmc_host/mmc0/mmc0:0001
/sys/devices/platform/bus@5b000000/5b010000.mmc/mmc_host/mmc0/mmc0:0001/block/mmcblk0
/sys/devices/platform/bus@5b000000/5b010000.mmc/mmc_host/mmc0/mmc0:0001/block/mmcblk0/mmcblk0boot0
/sys/devices/platform/bus@5b000000/5b010000.mmc/mmc_host/mmc0/mmc0:0001/block/mmcblk0/mmcblk0boot1
/sys/devices/platform/bus@5b000000/5b010000.mmc/mmc_host/mmc0/mmc0:0001/block/mmcblk0/mmcblk0p1
/sys/devices/platform/bus@5b000000/5b010000.mmc/mmc_host/mmc0/mmc0:0001/block/mmcblk0/mmcblk0p2
/sys/devices/platform/bus@5b000000/5b010000.mmc/mmc_host/mmc0/mmc0:0001/block/mmcblk0/mmcblk0p3
/sys/devices/platform/bus@5b000000/5b010000.mmc/mmc_host/mmc0/mmc0:0001/block/mmcblk0/mmcblk0p4
```
Boot time reduction with this is place is ~ 1 second.
man/udevadm.xml
shell-completion/bash/udevadm
shell-completion/zsh/_udevadm
src/libsystemd/libsystemd.sym
src/libsystemd/sd-device/device-enumerator.c
src/libsystemd/sd-device/test-sd-device.c
src/systemd/sd-device.h
src/udev/udevadm-trigger.c