| Summary: | Udev should not blacklist DEVTYPE changes in rules | ||
|---|---|---|---|
| Product: | systemd | Reporter: | Juho Östman <juho.ostman> |
| Component: | general | Assignee: | systemd-bugs |
| Status: | RESOLVED NOTABUG | QA Contact: | systemd-bugs |
| Severity: | normal | ||
| Priority: | medium | ||
| Version: | unspecified | ||
| Hardware: | x86-64 (AMD64) | ||
| OS: | Linux (All) | ||
| Whiteboard: | |||
| i915 platform: | i915 features: | ||
DEVTYPE is a primary kernel property which cannot be changed bu userspace. We cannot overwrite it or store other information in udev than the kernel, it will just create a huge mess. Tools using that information should be fixed, ot other properties introduced, but not kernel variables overwritten. |
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A couple of USB-attached mobile broadband routers can be used either as a modem or as a network interface. If the device is employed as a network interface, it suffices to ask for IP settings via DHCP, and no other initialization is necessary. The kernel driver assigns the DEVTYPE "wwan" for these devices, and this information is used by NetworkManager, for example, to decide which user-mode driver should be chosen to configure the interface. If the DEVTYPE is "wwan", the device is treated as a modem, on the other hand, if the DEVTYPE is "eth" or some unrecognized string, the interface is configured as a network interface. I have used an udev rule like this to select the correct behaviour: SUBSYSTEM=="net", ATTRS{idVendor}=="1199", ATTRS{idProduct}=="68a3", ENV{ID_MM_CANDIDATE}="0", ENV{DEVTYPE}="eth" Changing the DEVTYPE in a udev rule is the simplest way to choose how a device should be configured. Actually, NetworkManager does not currently provide any other way to affect the decision. Therefore, changing the DEVTYPE should not be blacklisted.