What if kernel CONFIG=Y or CONFIG=N and backports CONFIG=M?

What if kernel CONFIG=Y or CONFIG=N and backports CONFIG=M?

[Leon Woestenberg]

Hello all,

two questions (I am new to the backports project):

If I configure backports to build a driver as a module, whilst the 
kernel we build against (KLIB/KLIB_BUILD) has this driver built-in, what 
is supposed to happen?

Obviously I cannot load the backport module into the kernel.


Is it possible (within the kernel and backports code) to build a 
subsystem or driver as a module, if the original kernel did not have 
this subsystem or driver built at all ("N" in the menu, CONFIG_ 
commented out in .config)?

Can the kernel always load modules that were defined as =N during the 
kernel built itself?

(My aim is Yocto/OpenEmbedded support for backports into the build system.)

Thanks,

Leon.

Re: What if kernel CONFIG=Y or CONFIG=N and backports CONFIG=M?

[Luis R. Rodriguez]

On Wed, Jul 31, 2013 at 4:16 PM, Leon Woestenberg
<sidebranch.linux@gmail.com> wrote:
> Hello all,
>
> two questions (I am new to the backports project):
>
> If I configure backports to build a driver as a module, whilst the kernel we
> build against (KLIB/KLIB_BUILD) has this driver built-in, what is supposed
> to happen?

Well backports currently only allows =m for itself but non-modular
support is theoretically possible [0] and should be considered if its
a requirement.

[0] https://backports.wiki.kernel.org/index.php/Documentation/backports/hacking/todo#Non_modular_backport_support

Patches welcome :D lets kill stupid silly branching efforts on kernel
management efforts.

> Obviously I cannot load the backport module into the kernel.
>
>
> Is it possible (within the kernel and backports code) to build a subsystem
> or driver as a module, if the original kernel did not have this subsystem or
> driver built at all ("N" in the menu, CONFIG_ commented out in .config)?

Yes, however if the subsystem required certain requirements those
requirements will still be required. For example say your backported
driver needed CONFIG_PCI but you didn't enable it, CONFIG_PCI would
still be required.

> Can the kernel always load modules that were defined as =N during the kernel
> built itself?

Yes. Consider the case of *new* modules that were not available in
older kernels. We support that.

  Luis