From: Rusty Russell <rusty@rustcorp.com.au>
To: Greg KH <gregkh@suse.de>
Subject: Re: linux-next: rr tree build failure
Date: Mon, 24 Nov 2008 14:38:36 +1030
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Cc: Stephen Rothwell <sfr@canb.auug.org.au>, linux-kernel@vger.kernel.org,
       Pete Zaitcev <zaitcev@redhat.com>
References: <20081121141913.90d05091.sfr@canb.auug.org.au> <200811221301.07058.rusty@rustcorp.com.au> <20081122064132.GA6196@suse.de>
In-Reply-To: <20081122064132.GA6196@suse.de>
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On Saturday 22 November 2008 17:11:32 Greg KH wrote:
> On Sat, Nov 22, 2008 at 01:01:06PM +1030, Rusty Russell wrote:
> > Fair enough.  Patch below does this as moduleparam.h suggests.
> >
> > It still means that the paremeter appears in
> > /sys/module/kernel/parameters/nousb OR
> > /sys/module/usbcore/parameters/nousb.
>
> What's the "OR" part?  What determines where it goes?

Whether usbcore is a module or not, of course.

> > +/* To disable USB, kernel command line is 'nousb' not 'usbcore.nousb' */
> > +#undef MODULE_PARAM_PREFIX
> > +#define MODULE_PARAM_PREFIX
> > +module_param(nousb, bool, 0444);
>
> That undef seems hacky beyond belief.

*Exactly*.  And while you're not the first person to do this, you're the one 
one to use it for code which can be a module :(

> How would one know to do this?

The same way Pete found __module_param_call, by reading the header:

 /* You can override this manually, but generally this should match the
    module name. */
 #ifdef MODULE
 #define MODULE_PARAM_PREFIX /* empty */
 #else
 #define MODULE_PARAM_PREFIX KBUILD_MODNAME "."
 #endif

Cheers,
Rusty.
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