[systemd-devel] Utility for persistent alternative driver binding

[Panu Matilainen]

On 12/04/2015 04:41 PM, poma wrote:
> On 04.12.2015 15:27, poma wrote:
>> On 04.12.2015 10:40, Panu Matilainen wrote:
>>> Hi all,
>>>
>>> To follow-up on this thread from September-October:
>>> http://lists.freedesktop.org/archives/systemd-devel/2015-September/034427.html
>>> http://lists.freedesktop.org/archives/systemd-devel/2015-October/034551.html
>>>
>>> The driverctl utility has matured a bit from the earliest tyre-kicking
>>> version seen there and now lives at laiskiainen.org/git/?p=driverctl.git
>>>
>>> Since it has everything to do with udev this seems like a reasonable
>>> forum to advertise it a bit. Quoting from the README a bit:
>>>
>>>> driverctl is a tool for manipulating and inspecting the system
>>>> device driver choices.
>>>>
>>>> Devices are normally assigned to their sole designated kernel driver
>>>> by default. However in some situations it may be desireable to
>>>> override that default, for example to try an older driver to
>>>> work around a regression in a driver or to try an experimental alternative
>>>> driver. Another common use-case is pass-through drivers and driver
>>>> stubs to allow userspace to drive the device, such as in case of
>>>> virtualization.
>>>>
>>>> driverctl integrates with udev to support overriding
>>>> driver selection for both cold- and hotplugged devices from the
>>>> moment of discovery, but can also change already assigned drivers,
>>>> assuming they are not in use by the system. The driver overrides
>>>> created by driverctl are persistent across system reboots
>>>> by default.
>>>   >
>>>> Usage
>>>> -----
>>>>
>>>> Find devices currently driven by ixgbe driver:
>>>>
>>>> # driverctl -v list-devices | grep ixgbe
>>>> 0000:01:00.0 ixgbe (Ethernet 10G 4P X520/I350 rNDC)
>>>> 0000:01:00.1 ixgbe (Ethernet 10G 4P X520/I350 rNDC)
>>>>
>>>> Change them to use the vfio-pci driver:
>>>> # driverctl set-override 0000:01:00.0 vfio-pci
>>>> # driverctl set-override 0000:01:00.1 vfio-pci
>>>>
>>>> Find devices with driver overrides:
>>>> # driverctl -v list-devices|grep \\*
>>>> 0000:01:00.0 vfio-pci [*] (Ethernet 10G 4P X520/I350 rNDC)
>>>> 0000:01:00.1 vfio-pci [*] (Ethernet 10G 4P X520/I350 rNDC)
>>>>
>>>> Remove the override from slot 0000:01:00.1:
>>>> # driverctl unset-override 0000:01:00.1
>>>
>>> The other reason for posting here is: is there interest in having such a
>>> utility would find home in udev/systemd?
>>>
>>> Note that I'm not trying to sell you the current shell-spaghetti
>>> implementation, its mostly just a demonstration of the interface which
>>> is modeled after the various *ctl utilities in systemd. The idea is to
>>> rewrite it properly in C anyway, but at this point it'd be useful to
>>> know from style/infrastructure/etc perspective whether there's interest
>>> in having such a thing included in systemd afterall.
>>>
>>
>> version 0.2?
>> driverctl + udevadm + add/edit/test/del udev-rules files (rather than working with files directly) = udevctl™
>>
>>
>
> e.g.
> # udevctl --driver list-devices | set-override | unset-override ...
> # udevctl --admin control | hwdb | monitor ...
> # udevctl --rule add | edit | test | del ...
> ...
>

I personally have no aspirations to write a udev Swiss army knife.

It could of course write udev rules directly, the extra config file 
approach makes it simpler to manage, eg if the udev rule needs changing 
it can be easily changed in packaging instead of having to munge unknown 
number of udev configuration files on disk and hope not to trample any 
manually created rules in the process.

	- Panu -