From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from psmtp.com (na3sys010amx104.postini.com [74.125.245.104]) by kanga.kvack.org (Postfix) with SMTP id D30576B004F for ; Tue, 24 Jan 2012 11:25:59 -0500 (EST) From: Arnd Bergmann Subject: Re: [RFC 1/3] /dev/low_mem_notify Date: Tue, 24 Jan 2012 16:25:55 +0000 References: <1326788038-29141-1-git-send-email-minchan@kernel.org> <20120124154001.GB10990@amt.cnet> <1327420880.13624.24.camel@jaguar> In-Reply-To: <1327420880.13624.24.camel@jaguar> MIME-Version: 1.0 Content-Type: Text/Plain; charset="iso-8859-1" Content-Transfer-Encoding: 7bit Message-Id: <201201241625.55295.arnd@arndb.de> Sender: owner-linux-mm@kvack.org List-ID: To: Pekka Enberg Cc: Marcelo Tosatti , Rik van Riel , Minchan Kim , linux-mm , LKML , leonid.moiseichuk@nokia.com, kamezawa.hiroyu@jp.fujitsu.com, mel@csn.ul.ie, rientjes@google.com, KOSAKI Motohiro , Johannes Weiner , Andrew Morton , Ronen Hod , KOSAKI Motohiro On Tuesday 24 January 2012, Pekka Enberg wrote: > On Tue, 2012-01-24 at 13:40 -0200, Marcelo Tosatti wrote: > > What is the practical advantage of a syscall, again? > > Why do you ask? The advantage for this particular case is not needing to > add ioctls() for configuration and keeping the file read/write ABI > simple. The two are obviously equivalent and there is no reason to avoid ioctl in general. However I agree that the syscall would be better in this case, because that is what we tend to use for core kernel functionality, while character devices tend to be used for I/O device drivers that need stuff like enumeration and permission management. Arnd -- To unsubscribe, send a message with 'unsubscribe linux-mm' in the body to majordomo@kvack.org. For more info on Linux MM, see: http://www.linux-mm.org/ . Fight unfair telecom internet charges in Canada: sign http://stopthemeter.ca/ Don't email: email@kvack.org From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1755368Ab2AXQ0L (ORCPT ); Tue, 24 Jan 2012 11:26:11 -0500 Received: from moutng.kundenserver.de ([212.227.17.9]:49263 "EHLO moutng.kundenserver.de" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1755204Ab2AXQ0I (ORCPT ); Tue, 24 Jan 2012 11:26:08 -0500 From: Arnd Bergmann To: Pekka Enberg Subject: Re: [RFC 1/3] /dev/low_mem_notify Date: Tue, 24 Jan 2012 16:25:55 +0000 User-Agent: KMail/1.12.2 (Linux/3.2.0-rc7; KDE/4.3.2; x86_64; ; ) Cc: Marcelo Tosatti , Rik van Riel , Minchan Kim , "linux-mm" , LKML , leonid.moiseichuk@nokia.com, kamezawa.hiroyu@jp.fujitsu.com, mel@csn.ul.ie, rientjes@google.com, KOSAKI Motohiro , Johannes Weiner , Andrew Morton , Ronen Hod , KOSAKI Motohiro References: <1326788038-29141-1-git-send-email-minchan@kernel.org> <20120124154001.GB10990@amt.cnet> <1327420880.13624.24.camel@jaguar> In-Reply-To: <1327420880.13624.24.camel@jaguar> MIME-Version: 1.0 Content-Type: Text/Plain; charset="iso-8859-1" Content-Transfer-Encoding: 7bit Message-Id: <201201241625.55295.arnd@arndb.de> X-Provags-ID: V02:K0:jytNgZkXFiyyQ0+HID3nBpRdCqrSWxTR4ekwO7kDCMY OJAqY+dwEB9q7vVlJKW0XcZDO/0mHEzmIa7Ijc1MCPkXjLE8Fp ij1lLDJ2xmxhPqFmXR+ahnHk6AirCo70rQ/I1wijgDcBINn3/x S/2EM5s2gAvVfLsz5g2bgeg44vKXr+YFtarltDx398cQN169s5 xqHBKTpYps/6Q5BtcoL5fR4yWXu8BwxUVHH/SJIamyKo4m6/bn 70pkYVA74RCDqXpVYJMUbcYZceBNc+f/FiuHWjVwLscmIBn4yr jZPWsxX6ny/ybv+bA0Crxxe7R0cRJB/c6fLmaFs943j5EvcjP8 i2KldNiEa1yaC3r3BFOo= Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Tuesday 24 January 2012, Pekka Enberg wrote: > On Tue, 2012-01-24 at 13:40 -0200, Marcelo Tosatti wrote: > > What is the practical advantage of a syscall, again? > > Why do you ask? The advantage for this particular case is not needing to > add ioctls() for configuration and keeping the file read/write ABI > simple. The two are obviously equivalent and there is no reason to avoid ioctl in general. However I agree that the syscall would be better in this case, because that is what we tend to use for core kernel functionality, while character devices tend to be used for I/O device drivers that need stuff like enumeration and permission management. Arnd