From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from mail.kernel.org ([198.145.29.99]:55672 "EHLO mail.kernel.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1732604AbfIELQY (ORCPT ); Thu, 5 Sep 2019 07:16:24 -0400 Date: Thu, 5 Sep 2019 13:16:17 +0200 From: Jessica Yu Subject: Re: [usb-storage] Re: [PATCH v4 12/12] RFC: watchdog: export core symbols in WATCHDOG_CORE namespace Message-ID: <20190905111617.GB27788@linux-8ccs> References: <20180716122125.175792-1-maco@android.com> <20190903150638.242049-1-maennich@google.com> <20190903150638.242049-13-maennich@google.com> <20190903161045.GA22754@roeck-us.net> <20190905104147.GA27788@linux-8ccs> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii; format=flowed Content-Disposition: inline In-Reply-To: Sender: linux-kbuild-owner@vger.kernel.org List-ID: To: Arnd Bergmann Cc: Matthew Dharm , Guenter Roeck , Masahiro Yamada , Matthias Maennich , Linux Kernel Mailing List , "Cc: Android Kernel" , Greg Kroah-Hartman , "Joel Fernandes (Google)" , Lucas De Marchi , Martijn Coenen , Sandeep Patil , Will Deacon , Linux Kbuild mailing list , linux-modules@vger.kernel.org, linux-usb , USB Mass Storage on Linux , LINUXWATCHDOG +++ Arnd Bergmann [05/09/19 12:52 +0200]: >On Thu, Sep 5, 2019 at 12:41 PM Jessica Yu wrote: >> +++ Matthew Dharm [04/09/19 09:16 -0700]: >> >On Wed, Sep 4, 2019 at 5:12 AM Guenter Roeck wrote: > >> >HOWEVER, I have one question: If these patches are included, and >> >someone wants to introduce a bit of code which needs to use two >> >symbols from different namespaces but with the same name, can that be >> >done? That is, if driver A has symbol 'foo' and driver B has symbol >> >'foo' (both in their respective namespaces), and driver C wants to use >> >A.foo and B.foo, can that be supported? >> >> As of now, we currently don't support this - modpost will warn if a >> symbol is exported more than once (across modules + vmlinux), and the >> module loader currently assumes exported symbol names are unique. Do >> you have a concrete use case? If there is a strong need for this, I >> don't think it'd be too hard to implement. > >I think what would prevent this from working in general is that having >two modules with the same exported symbol in different namespaces >won't link if you try to build both modules into the kernel itself. > > Arnd Ah yeah, you are right. I only tried building an identically named exported symbol in a module and in the kernel, and there I got away with a modpost warning. But this breaks when building the module into the kernel, so I guess this is out of the question. Thanks, Jessica