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SubjectRe: [RFC PATCH] Allow optional module parameters
Date
Andy Lutomirski <luto@amacapital.net> writes:
> Current parameter behavior is odd. Boot parameters that have values
> and don't match anything become environment variables, with no
> warning. Boot parameters without values that don't match anything
> go into argv_init. Everything goes into /proc/cmdline.
>
> The init_module and finit_module syscalls, however, are strict:
> parameters that don't match result in -ENOENT.
>
> kmod (and hence modprobe), when loading a module called foo, look in
> /proc/cmdline for foo.x or foo.x=y, strip off the foo., and pass the
> rest to init_module.
>
> The upshot is that booting with module.nonexistent_parameter=1 is
> okay if module is built in or missing entirely but prevents module
> from loading if it's an actual module. Similarly, option module
> nonexistent_parameter=1 in /etc/modprobe.d prevents the module from
> loading the parameter goes away. This means that removing module
> parameters unnecessarily breaks things.

Err, yes. Don't remove module parameters, they're part of the API. Do
you have a particular example?

> With this patch, module parameters can be made explicitly optional.
> This approach is IMO silly, but it's unlikely to break anything,
> since I doubt that anyone needs init parameters or init environment
> variables that end in a tilde.

It's silly for the removal problem: that should be handled in the
kernel. How would the poor user know that the option is going away?
So how about we add a module_param_obsolete(name) macro?

If a parameter were introduced, and the user wanted to specify it *if*
it was supported, that might justify this approach rather than using
complex install commands. But I don't believe that's common, is it?

Thanks,
Rusty.


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