Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1752173Ab3COFEJ (ORCPT ); Fri, 15 Mar 2013 01:04:09 -0400 Received: from ozlabs.org ([203.10.76.45]:53406 "EHLO ozlabs.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751296Ab3COFEF (ORCPT ); Fri, 15 Mar 2013 01:04:05 -0400 From: Rusty Russell To: Andy Lutomirski , linux-kernel@vger.kernel.org Cc: Andy Lutomirski Subject: Re: [RFC PATCH] Allow optional module parameters In-Reply-To: References: User-Agent: Notmuch/0.14 (http://notmuchmail.org) Emacs/23.4.1 (i686-pc-linux-gnu) Date: Fri, 15 Mar 2013 15:33:32 +1030 Message-ID: <87ehfhtftn.fsf@rustcorp.com.au> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 1988 Lines: 43 Andy Lutomirski 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. -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/