[elrepo-devel] how to require a kernel module

[Dag Wieers]

On Wed, 17 Feb 2010, Farkas Levente wrote:

> On 02/17/2010 04:34 PM, Akemi Yagi wrote:
>> On Wed, Feb 17, 2010 at 5:32 AM, Farkas Levente<lfarkas at lfarkas.org>  wrote:
>>> hi,
>>> now we've a lot's of kernel module and we can build our own on a nearly
>>> standardized way for rhel/centos. but i now run into a problem how to
>>> add a require kmod line into another package's spec file. it seems to
>>> very easy, if i've got package x.spec:
>>> Requires: y-kmod
>>> but now comes whether y-kmod or kmod-y (tha package name or the virtual
>>> provides)? and if we go a bit further and have a i386 machine with 4gb
>>> ram which install by default kernel-PAE and like to install x into that
>>> machine i wish to pull (yum pull) kmod-x-PAE and not kmod-x since it
>>> can't be used on a PAE kernel. what's more if x pull kmod-y that also
>>> pull the none PAE kernel too which is also not a good think.
>>> so what's the good and proper solution to require y kernel module into
>>> package x (in a way that works with yum on all kernel variant)?
>>> anybody has any solution to this?
>>
>> The kernel type such as PAE and xen are defined first in
>> 'knownvariants' in kmodtool. Then there is subsequently 'dashvariant'
>> that is used to pull the appropriate kernel-(type)-devel as in:
>>
>> echo "BuildRequires: kernel${dashvariant}-devel-%{_target_cpu} = ${verrel}"
>>
>> So, something similar can be applied ?
>
> in the kmod package spec file of course, but in an independent package
> it's not working (even kmodtool not included etc).
> it should have to discover the running system's 'dashvariant' and
> install the proper rpm. so some kind of virtual provides would be
> required...

I don't think you can do this :-( The problem is that if you have a 
seperate package that requires a kmod package, you are not interested 
whether one kernel variant is installed (eg. Requires: ocfs2-kmod) or 
whether a specific kernel variant is installed (eg.: Requires: 
kmod-ocfs2-PAE), you are basically interested in whether the kmod for your 
running kernel is installed.

And that is simply not possible with RPM packages. You could hijack a 
pre-script to bail out when your condition is not met, but how that 
interacts with an RPM transaction set including more than one package, and 
depsolver behaviour, I doubt that is advisable.

The best way is to check if the kmod is installed in general, assume it 
works for the current kernel, and assume it is loaded (which is another 
step that you cannot check as part of dependencies) and hope the tool 
requiring the kernel module does its own checks and proper reporting.

Kind regards,
-- 
--   dag wieers,  dag at wieers.com,  http://dag.wieers.com/   --
[Any errors in spelling, tact or fact are transmission errors]