Udev, hal and loading of modules
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Hello.
I've recently developed an addon for hal enabling backlight on dell machines to be controlled via dbus/hal. The catch right now is that the "dcdbas" linux kernel module needs to be loaded for the addon to work.
My question is if there is a way for hal to suggest to udev what modules to load? Or are there better alternatives, such as udev probing the smbios (via dmidecode) and load the module that way?
Thanks in advance
Erik Andrén
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Quoted 7 lines · Erik Andrén
I've recently developed an addon for hal enabling backlight on dell machines to be controlled via dbus/hal. The catch right now is that the "dcdbas" linux kernel module needs to be loaded for the addon to work.
My question is if there is a way for hal to suggest to udev what modules to load? Or are there better alternatives, such as udev probing the smbios (via dmidecode) and load the module that way?
Udev loads only modules, which are suggested by a MODALIAS value supplied by the kernel. There is no generic infrastructure in udev to load any module depending on other properties. Unfortunately, there is no solution today; it's up to the distro tools to add an entry to some file to load such modules unconditionally.
Kay
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Quoted 5 lines · Kay Sievers
Quoted 4 lines · Erik Andrén
I've recently developed an addon for hal enabling backlight on dell machines to be controlled via dbus/hal. The catch right now is that the "dcdbas" linux kernel module needs to be loaded for the addon to work.
Quoted 7 lines
Quoted 3 lines
My question is if there is a way for hal to suggest to udev what modules to load? Or are there better alternatives, such as udev probing the smbios (via dmidecode) and load the module that way?
Udev loads only modules, which are suggested by a MODALIAS value supplied by the kernel. There is no generic infrastructure in udev to load any module depending on other properties.
Supposedly
- the kernel could export some node in sysfs describing the system (akin to HAL's computer root object); for smbios it would contain some DMI data; for other machine types it would contain something else (e.g. EFI)
- modules like dcdbas could suggest a MODALIAS value and we could match this on the system node
- udev would load the driver on matches
How about that?
Quoted 3 lines
Unfortunately, there is
no solution today; it's up to the distro tools to add an entry to some file to load such modules unconditionally.
This sucks and therefore we should change it.
David
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Quoted 9 lines · David Zeuthen
Quoted 8 lines · Kay Sievers
Quoted 7 lines · Erik Andrén
I've recently developed an addon for hal enabling backlight on dell machines to be controlled via dbus/hal. The catch right now is that the "dcdbas" linux kernel module needs to be loaded for the addon to work.
My question is if there is a way for hal to suggest to udev what modules to load? Or are there better alternatives, such as udev probing the smbios (via dmidecode) and load the module that way?
On which property would we match? That it's a Dell Laptop? Or a specific model?
Quoted 11 lines
Quoted 3 lines
Udev loads only modules, which are suggested by a MODALIAS value supplied by the kernel. There is no generic infrastructure in udev to load any module depending on other properties.
Supposedly
- the kernel could export some node in sysfs describing the system (akin to HAL's computer root object); for smbios it would contain some DMI data; for other machine types it would contain something else (e.g. EFI)
Quoted 6 lines
- modules like dcdbas could suggest a MODALIAS value and we could match this on the system node
- udev would load the driver on matches
How about that?
Maybe, if the values in smbios can be used as a wildcard, to match a modalias contained in the module.
But there once was a try to export smbios properties in /proc, but that never made it somewhere, because userspace could handle it just fine by reading /dev/mem ...
Quoted 5 lines
Quoted 3 lines
Unfortunately, there is
no solution today; it's up to the distro tools to add an entry to some file to load such modules unconditionally.This sucks and therefore we should change it.
We probably just want a static list, that is composed by some program that reads smbios values and stores the needed modulelist on disk, to load modules unconditionally?
I wouldn't mind, to put such a list in /etc/udev/<whatever> and load all these modules with the udev init-script at every bootup.
Thanks,
Kay
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