From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S932420Ab3AJHLo (ORCPT ); Thu, 10 Jan 2013 02:11:44 -0500 Received: from mga11.intel.com ([192.55.52.93]:64721 "EHLO mga11.intel.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S932160Ab3AJHLn (ORCPT ); Thu, 10 Jan 2013 02:11:43 -0500 X-ExtLoop1: 1 X-IronPort-AV: E=Sophos;i="4.84,442,1355126400"; d="scan'208";a="272133555" Date: Thu, 10 Jan 2013 15:12:23 +0800 From: Yuanhan Liu To: Stefani Seibold Cc: linux-kernel@vger.kernel.org, Andrew Morton Subject: Re: [PATCH 1/5] kfifo: remove unnecessary type check Message-ID: <20130110071223.GE304@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> <1357745379.11538.4.camel@wall-e> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <1357745379.11538.4.camel@wall-e> 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 On Wed, Jan 09, 2013 at 04:29:39PM +0100, Stefani Seibold wrote: > 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. Well, the fact is struct kfifo is used far more widely than DECLARE/DEFINE_KFIFO; say above 50 vs less than 10. Thanks. --yliu > > 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 >