如何查找未应用 udev 规则的原因？

Question

我添加了一个 udev 规则来生成到特殊 tty 设备的单独链接。我从 lsusb 获取了供应商和产品 ID：

Bus 001 Device 016: ID abcd:1234 Foo Device

该dmesg设备的输出是：

[  369.384850] usb 1-1.1: new full-speed USB device number 4 using xhci_hcd
[  369.470492] usb 1-1.1: New USB device found, idVendor=09d8, idProduct=0420
[  369.470506] usb 1-1.1: New USB device strings: Mfr=1, Product=2, SerialNumber=0
[  369.470515] usb 1-1.1: Product: TWN4/B1.06/CCL3.12/PRS1.04
[  369.470522] usb 1-1.1: Manufacturer: OEM
[  369.475188] cdc_acm 1-1.1:1.0: ttyACM0: USB ACM device

通常 Debian 系统会为此设备生成一个 ACM* tty：

$ ls /dev/ttyACM*
/dev/ttyACM0

所以我创建了/ect/udev/rules.d/99-bizrfid.rules：

ACTION=="add", ATTRS{idVendor}=="09d8", ATTRS{idProduct}=="0420", SYMLINK+="ttyMyDevice"

但ls /dev/tty*不显示ttyMyDevice。

到目前为止我尝试过但没有成功：

1. 跑步udevadm trigger。这应该应用新的 udev 规则。
2. 我重新启动了。
3. 我看了看udevadm test /dev/ttyACM0。我的 udevrule 显示在最后。所以我确信它没有被覆盖。但我想知道“无法打开”提示。然而，此提示也适用于其他 tty，例如 tty0 或 ttyS0。

...    
Reading rules file: /lib/udev/rules.d/98-systemd.rules
Reading rules file: /etc/udev/rules.d/99-bizrfid.rules
rules contain 49152 bytes tokens (4096 * 12 bytes), 12883 bytes strings
4240 strings (40079 bytes), 3515 de-duplicated (27922 bytes), 726 trie nodes used
unable to open device '/sys/dev/ttyACM0'
Unload module index
Unloaded link configuration context.

4. 我重新连接了 USB 设备。
5. 我尝试了另一个 udev 规则。这个规则 100% 正确，因为我已经在其他设备上使用了这个规则。但它不适用于 ttyACM0：

ACTION=="add", KERNEL=="ttyACM*", MODE="0666"

我想知道为什么这不起作用。 如何查找未应用 udev 规则的原因？

Answer 1

根据评论，我可以尝试以下方法来调试问题：

检查驱动程序

用于dmesg检查您正在使用的驱动程序并确保它是通用驱动程序。如果它是自定义编译的，则问题可能出在您的自定义实现内部。如果是通用的，请继续第二步。我在最后一行找到了驱动程序名称：cdc_acm

[  369.384850] usb 1-1.1: new full-speed USB device number 4 using xhci_hcd
[  369.470492] usb 1-1.1: New USB device found, idVendor=09d8, idProduct=0420
[  369.470506] usb 1-1.1: New USB device strings: Mfr=1, Product=2, SerialNumber=0
[  369.470515] usb 1-1.1: Product: TWN4/B1.06/CCL3.12/PRS1.04
[  369.470522] usb 1-1.1: Manufacturer: OEM
[  369.475188] cdc_acm 1-1.1:1.0: ttyACM0: USB ACM device

检查用户权限

确保您的 udev 规则的权限正确：

chmod 644 99-myrule.rules
chown root:root 99-myrule.rules

为添加操作进行测试运行

检查 的输出udevadm test -a add $(udevadm info -q path -n /dev/ttyACM0)。我的输出如下所示：

调用：测试

version 232
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.

=== trie on-disk ===
tool version:          232
file size:         8447696 bytes
header size             80 bytes
strings            1849040 bytes
nodes              6598576 bytes
Load module index
Found container virtualization none
timestamp of '/etc/systemd/network' changed
timestamp of '/usr/lib/systemd/network' changed
timestamp of '/lib/systemd/network' changed
Parsed configuration file /lib/systemd/network/99-default.link
Created link configuration context.
timestamp of '/etc/udev/rules.d' changed
Skipping overridden file: /lib/udev/rules.d/99-bizrfid.rules.
Reading rules file: /lib/udev/rules.d/50-firmware.rules

...

Reading rules file: /lib/udev/rules.d/98-systemd.rules
Reading rules file: /etc/udev/rules.d/99-bizrfid.rules
rules contain 49152 bytes tokens (4096 * 12 bytes), 12900 bytes strings
4244 strings (40114 bytes), 3517 de-duplicated (27942 bytes), 728 trie nodes used
GROUP 20 /lib/udev/rules.d/50-udev-default.rules:26
IMPORT builtin 'hwdb' /lib/udev/rules.d/60-serial.rules:7
IMPORT builtin 'usb_id' /lib/udev/rules.d/60-serial.rules:8
/sys/devices/pci0000:00/0000:00:14.0/usb1/1-1/1-1.1/1-1.1:1.0: if_class 2 protocol 0
IMPORT builtin 'hwdb' /lib/udev/rules.d/60-serial.rules:8
IMPORT builtin 'path_id' /lib/udev/rules.d/60-serial.rules:15
LINK 'serial/by-path/pci-0000:00:14.0-usb-0:1.1:1.0' /lib/udev/rules.d/60-serial.rules:16
IMPORT builtin skip 'usb_id' /lib/udev/rules.d/60-serial.rules:19
LINK 'serial/by-id/usb-OEM_TWN4_B1.06_CCF3.00_PRS1.04-if00' /lib/udev/rules.d/60-serial.rules:23
LINK 'ttyMyDevice' /etc/udev/rules.d/99-bizrfid.rules:1
handling device node '/dev/ttyACM0', devnum=c166:0, mode=0660, uid=0, gid=20
preserve permissions /dev/ttyACM0, 020660, uid=0, gid=20
preserve already existing symlink '/dev/char/166:0' to '../ttyACM0'
found 'c166:0' claiming '/run/udev/links/\x2fserial\x2fby-id\x2fusb-OEM_TWN4_B1.06_CCF3.00_PRS1.04-if00'
creating link '/dev/serial/by-id/usb-OEM_TWN4_B1.06_CCF3.00_PRS1.04-if00' to '/dev/ttyACM0'
preserve already existing symlink '/dev/serial/by-id/usb-OEM_TWN4_B1.06_CCF3.00_PRS1.04-if00' to '../../ttyACM0'
found 'c166:0' claiming '/run/udev/links/\x2fserial\x2fby-path\x2fpci-0000:00:14.0-usb-0:1.1:1.0'
creating link '/dev/serial/by-path/pci-0000:00:14.0-usb-0:1.1:1.0' to '/dev/ttyACM0'
preserve already existing symlink '/dev/serial/by-path/pci-0000:00:14.0-usb-0:1.1:1.0' to '../../ttyACM0'
creating link '/dev/ttyMyDevice' to '/dev/ttyACM0'
creating symlink '/dev/ttyMyDevice' to 'ttyACM0'
created db file '/run/udev/data/c166:0' for '/devices/pci0000:00/0000:00:14.0/usb1/1-1/1-1.1/1-1.1:1.0/tty/ttyACM0'
ACTION=add
DEVLINKS=/dev/serial/by-path/pci-0000:00:14.0-usb-0:1.1:1.0 /dev/serial/by-id/usb-OEM_TWN4_B1.06_CCF3.00_PRS1.04-if00 /dev/ttyMyDevice
DEVNAME=/dev/ttyACM0
DEVPATH=/devices/pci0000:00/0000:00:14.0/usb1/1-1/1-1.1/1-1.1:1.0/tty/ttyACM0
ID_BUS=usb
ID_MODEL=TWN4_B1.06_CCF3.00_PRS1.04
ID_MODEL_ENC=TWN4\x2fB1.06\x2fCCF3.00\x2fPRS1.04
ID_MODEL_FROM_DATABASE=Atom Processor Z36xxx/Z37xxx, Celeron N2000 Series USB xHCI
ID_MODEL_ID=0420
ID_PATH=pci-0000:00:14.0-usb-0:1.1:1.0
ID_PATH_TAG=pci-0000_00_14_0-usb-0_1_1_1_0
ID_PCI_CLASS_FROM_DATABASE=Serial bus controller
ID_PCI_INTERFACE_FROM_DATABASE=XHCI
ID_PCI_SUBCLASS_FROM_DATABASE=USB controller
ID_REVISION=0200
ID_SERIAL=OEM_TWN4_B1.06_CCF3.00_PRS1.04
ID_TYPE=generic
ID_USB_CLASS_FROM_DATABASE=Communications
ID_USB_DRIVER=cdc_acm
ID_USB_INTERFACES=:020201:0a0000:
ID_USB_INTERFACE_NUM=00
ID_VENDOR=OEM
ID_VENDOR_ENC=OEM
ID_VENDOR_FROM_DATABASE=Intel Corporation
ID_VENDOR_ID=09d8
MAJOR=166
MINOR=0
SUBSYSTEM=tty
TAGS=:systemd:
USEC_INITIALIZED=71480300178
Unload module index
Unloaded link configuration context.

Answer 2

对于udev规则 /ect/udev/rules.d/99-bizrfid.rules我会添加SUBSYSTEM：

ACTION=="add", SUBSYSTEM=="tty", ATTRS{idVendor}=="09d8", ATTRS{idProduct}=="0420", SYMLINK+="ttyMyDevice"

您还可以添加ATTRS{manufacturer}==，但idVendor和idProduct就足够了。

否则它看起来是正确的并且测试运行会创建符号链接：

creating link '/dev/ttyMyDevice' to '/dev/ttyACM0'