Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1756079Ab2JZDxE (ORCPT ); Thu, 25 Oct 2012 23:53:04 -0400 Received: from zeniv.linux.org.uk ([195.92.253.2]:50597 "EHLO ZenIV.linux.org.uk" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1755508Ab2JZDxB (ORCPT ); Thu, 25 Oct 2012 23:53:01 -0400 Date: Fri, 26 Oct 2012 04:52:59 +0100 From: Al Viro To: Linus Torvalds Cc: Ming Lei , Greg Kroah-Hartman , linux-kernel@vger.kernel.org Subject: Re: [PATCH v1] firmware loader: introduce module parameter to customize fw search path Message-ID: <20121026035259.GO2616@ZenIV.linux.org.uk> References: <1351212379-26026-1-git-send-email-ming.lei@canonical.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: User-Agent: Mutt/1.5.21 (2010-09-15) Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 1185 Lines: 24 On Thu, Oct 25, 2012 at 08:38:25PM -0700, Linus Torvalds wrote: > It's valid to cast a non-const pointer to a const one. It's the > *other* way around that is invalid. > > So marking fw_path[] as having 'const char *' elements just means that > we won't be changing those elements through the fw_path[] array > (correct: we only read them). The fact that one of those same pointers > is then also available through a non-const pointer variable means that > they can change through *that* pointer, but that doesn't change the > fact that fw_path[] itself contains const pointers. > > Remember: in C, a "const pointer" does *not* mean that the thing it > points to cannot change. It only means that it cannot change through > *that* pointer. It's a bit trickier, unfortunately - pointer to pointer to const char and pointer to pointer to char do not mix. Just for fun, try to constify envp and argv arguments of call_usermodehelper()... -- 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/