From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1758049Ab3AIPaU (ORCPT ); Wed, 9 Jan 2013 10:30:20 -0500 Received: from www84.your-server.de ([213.133.104.84]:59951 "EHLO www84.your-server.de" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1757904Ab3AIPaS (ORCPT ); Wed, 9 Jan 2013 10:30:18 -0500 Message-ID: <1357745379.11538.4.camel@wall-e> Subject: Re: [PATCH 1/5] kfifo: remove unnecessary type check From: Stefani Seibold To: Yuanhan Liu Cc: linux-kernel@vger.kernel.org, Andrew Morton Date: Wed, 09 Jan 2013 16:29:39 +0100 In-Reply-To: <20130109023503.GC304@yliu-dev.sh.intel.com> References: <1357657073-27352-1-git-send-email-yuanhan.liu@linux.intel.com> <1357657073-27352-2-git-send-email-yuanhan.liu@linux.intel.com> <1357681864.27255.5.camel@wall-e> <20130109023503.GC304@yliu-dev.sh.intel.com> Content-Type: text/plain; charset="ISO-8859-15" X-Mailer: Evolution 3.6.2 Mime-Version: 1.0 Content-Transfer-Encoding: 7bit X-Authenticated-Sender: stefani@seibold.net Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Am Mittwoch, den 09.01.2013, 10:35 +0800 schrieb Yuanhan Liu: > On Tue, Jan 08, 2013 at 10:51:04PM +0100, Stefani Seibold wrote: > > Am Dienstag, den 08.01.2013, 22:57 +0800 schrieb Yuanhan Liu: > > > Firstly, this kind of type check doesn't work. It does something similar > > > as following: > > > void * __dummy = NULL; > > > __buf = __dummy; > > > > > > __dummy is defined as void *. Thus it will not trigger warnings as > > > expected. > > > > > > Second, we don't need that kind of check. Since the prototype > > > of __kfifo_out is: > > > unsigned int __kfifo_out(struct __kfifo *fifo, void *buf, unsigned int len) > > > > > > buf is defined as void *, so we don't need do the type check. Remove it. > > > > > > > Thats wrong. > > > > First the type checking will be used in kfifo_put() and kfifo_in() for > > const types to check if the passed type of the data can converted to the > > fifo element type. > > Hi Stefani, > > Yes, I see now. After rechecking the code, I found that this kind of > type checking only works for those static defined kifo by > DECLARE/DEFINE_KFIFO. As the ptrtype is the same as the data type: > > /* the 4th argument "type" is "ptrtype" */ > #define STRUCT_KFIFO(type, size) struct __STRUCT_KFIFO(type, size, 0, type) > > #define DECLARE_KFIFO(fifo, type, size) STRUCT_KFIFO(type, size) fifo > > While, for those kfifo dynamically allocated, the type checking will not > work as expected then as ptrtype is always "void": > > struct kfifo __STRUCT_KFIFO_PTR(unsigned char, 0, void); > You should avoid using struct kfifo, as you can read in kfifo.h this is only for compatibility reason. If you use the macro DECLARE_KFIFO_PTR(), DECLARE_KFIFO() or DEFINE_KFIFO() instead. Have a look at the examples files in the samples/kfifo directory. - Stefani