From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1752817Ab1AXVBx (ORCPT ); Mon, 24 Jan 2011 16:01:53 -0500 Received: from mgw2.diku.dk ([130.225.96.92]:42138 "EHLO mgw2.diku.dk" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1752124Ab1AXVBw (ORCPT ); Mon, 24 Jan 2011 16:01:52 -0500 Date: Mon, 24 Jan 2011 22:01:46 +0100 (CET) From: Julia Lawall To: Ryan Mallon Cc: Vasiliy Kulikov , Russell King , kernel-janitors@vger.kernel.org, Nicolas Ferre , Jean-Christophe PLAGNIOL-VILLARD , Andrew Victor , linux-arm-kernel@lists.infradead.org, linux-kernel@vger.kernel.org Subject: Re: [PATCH 2/4] arch/arm/mach-at91/clock.c: Add missing IS_ERR test In-Reply-To: <4D3DE35B.1030102@bluewatersys.com> Message-ID: References: <1295898922-18822-1-git-send-email-julia@diku.dk> <1295898922-18822-3-git-send-email-julia@diku.dk> <4D3DD964.9020107@bluewatersys.com> <20110124200515.GA30963@albatros> <4D3DDD07.1030809@bluewatersys.com> <4D3DE35B.1030102@bluewatersys.com> MIME-Version: 1.0 Content-Type: TEXT/PLAIN; charset=US-ASCII Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Tue, 25 Jan 2011, Ryan Mallon wrote: > On 01/25/2011 09:28 AM, Julia Lawall wrote: > >> Julia is correct. Some architectures can return NULL from clk_get, but I > >> didn't check the at91 before posting :-/. If we can't return NULL from > >> clk_get then we shouldn't bother checking for it. I do think we should > >> drop the !IS_ERR(clk_get(dev, func)) check though. > > > > It seems a bit subtle, because the clk manipulated by clk_get in the call > > of clk_get(dev, func) is not necessarily the same as the one in > > clock_associate. But perhaps this is the only possibility in practice? > > Not sure I follow. The at91 clk_get does not modify the clk. In > at91_clock_associate we have: > > clk->function = func; > clk->dev = dev; > > and in clk_get we have: > > if (clk->function && (dev == clk->dev) && > strcmp(id, clk->function) == 0) > return clk; > > So at91_clock_associate sets the function for a clock, and clk_get > returns clocks based on the function association if the name lookup > fails. The only caveat to this is that the the clock function name > (clk->function) is not the same as any others clock's clk->name. Right, that was what I was worried about. That one would find the same information already present but somewhere else. But perhaps it can't happen, or it doesn't matter if it does? julia > The !IS_ERR(clk_get(dev, func)) check in at91_clock_associate just > appears to check that the clock is not already associated with the given > function. We don't really need this check because we are just making the > same assignment anyway. > > ~Ryan > > -- > Bluewater Systems Ltd - ARM Technology Solution Centre > > Ryan Mallon 5 Amuri Park, 404 Barbadoes St > ryan@bluewatersys.com PO Box 13 889, Christchurch 8013 > http://www.bluewatersys.com New Zealand > Phone: +64 3 3779127 Freecall: Australia 1800 148 751 > Fax: +64 3 3779135 USA 1800 261 2934 > -- > To unsubscribe from this list: send the line "unsubscribe kernel-janitors" in > the body of a message to majordomo@vger.kernel.org > More majordomo info at http://vger.kernel.org/majordomo-info.html > From mboxrd@z Thu Jan 1 00:00:00 1970 From: Julia Lawall Date: Mon, 24 Jan 2011 21:01:46 +0000 Subject: Re: [PATCH 2/4] arch/arm/mach-at91/clock.c: Add missing IS_ERR test Message-Id: List-Id: References: <1295898922-18822-1-git-send-email-julia@diku.dk> <1295898922-18822-3-git-send-email-julia@diku.dk> <4D3DD964.9020107@bluewatersys.com> <20110124200515.GA30963@albatros> <4D3DDD07.1030809@bluewatersys.com> <4D3DE35B.1030102@bluewatersys.com> In-Reply-To: <4D3DE35B.1030102@bluewatersys.com> MIME-Version: 1.0 Content-Type: text/plain; charset="us-ascii" Content-Transfer-Encoding: 7bit To: linux-arm-kernel@lists.infradead.org On Tue, 25 Jan 2011, Ryan Mallon wrote: > On 01/25/2011 09:28 AM, Julia Lawall wrote: > >> Julia is correct. Some architectures can return NULL from clk_get, but I > >> didn't check the at91 before posting :-/. If we can't return NULL from > >> clk_get then we shouldn't bother checking for it. I do think we should > >> drop the !IS_ERR(clk_get(dev, func)) check though. > > > > It seems a bit subtle, because the clk manipulated by clk_get in the call > > of clk_get(dev, func) is not necessarily the same as the one in > > clock_associate. But perhaps this is the only possibility in practice? > > Not sure I follow. The at91 clk_get does not modify the clk. In > at91_clock_associate we have: > > clk->function = func; > clk->dev = dev; > > and in clk_get we have: > > if (clk->function && (dev = clk->dev) && > strcmp(id, clk->function) = 0) > return clk; > > So at91_clock_associate sets the function for a clock, and clk_get > returns clocks based on the function association if the name lookup > fails. The only caveat to this is that the the clock function name > (clk->function) is not the same as any others clock's clk->name. Right, that was what I was worried about. That one would find the same information already present but somewhere else. But perhaps it can't happen, or it doesn't matter if it does? julia > The !IS_ERR(clk_get(dev, func)) check in at91_clock_associate just > appears to check that the clock is not already associated with the given > function. We don't really need this check because we are just making the > same assignment anyway. > > ~Ryan > > -- > Bluewater Systems Ltd - ARM Technology Solution Centre > > Ryan Mallon 5 Amuri Park, 404 Barbadoes St > ryan@bluewatersys.com PO Box 13 889, Christchurch 8013 > http://www.bluewatersys.com New Zealand > Phone: +64 3 3779127 Freecall: Australia 1800 148 751 > Fax: +64 3 3779135 USA 1800 261 2934 > -- > To unsubscribe from this list: send the line "unsubscribe kernel-janitors" in > the body of a message to majordomo@vger.kernel.org > More majordomo info at http://vger.kernel.org/majordomo-info.html > From mboxrd@z Thu Jan 1 00:00:00 1970 From: julia@diku.dk (Julia Lawall) Date: Mon, 24 Jan 2011 22:01:46 +0100 (CET) Subject: [PATCH 2/4] arch/arm/mach-at91/clock.c: Add missing IS_ERR test In-Reply-To: <4D3DE35B.1030102@bluewatersys.com> References: <1295898922-18822-1-git-send-email-julia@diku.dk> <1295898922-18822-3-git-send-email-julia@diku.dk> <4D3DD964.9020107@bluewatersys.com> <20110124200515.GA30963@albatros> <4D3DDD07.1030809@bluewatersys.com> <4D3DE35B.1030102@bluewatersys.com> Message-ID: To: linux-arm-kernel@lists.infradead.org List-Id: linux-arm-kernel.lists.infradead.org On Tue, 25 Jan 2011, Ryan Mallon wrote: > On 01/25/2011 09:28 AM, Julia Lawall wrote: > >> Julia is correct. Some architectures can return NULL from clk_get, but I > >> didn't check the at91 before posting :-/. If we can't return NULL from > >> clk_get then we shouldn't bother checking for it. I do think we should > >> drop the !IS_ERR(clk_get(dev, func)) check though. > > > > It seems a bit subtle, because the clk manipulated by clk_get in the call > > of clk_get(dev, func) is not necessarily the same as the one in > > clock_associate. But perhaps this is the only possibility in practice? > > Not sure I follow. The at91 clk_get does not modify the clk. In > at91_clock_associate we have: > > clk->function = func; > clk->dev = dev; > > and in clk_get we have: > > if (clk->function && (dev == clk->dev) && > strcmp(id, clk->function) == 0) > return clk; > > So at91_clock_associate sets the function for a clock, and clk_get > returns clocks based on the function association if the name lookup > fails. The only caveat to this is that the the clock function name > (clk->function) is not the same as any others clock's clk->name. Right, that was what I was worried about. That one would find the same information already present but somewhere else. But perhaps it can't happen, or it doesn't matter if it does? julia > The !IS_ERR(clk_get(dev, func)) check in at91_clock_associate just > appears to check that the clock is not already associated with the given > function. We don't really need this check because we are just making the > same assignment anyway. > > ~Ryan > > -- > Bluewater Systems Ltd - ARM Technology Solution Centre > > Ryan Mallon 5 Amuri Park, 404 Barbadoes St > ryan at bluewatersys.com PO Box 13 889, Christchurch 8013 > http://www.bluewatersys.com New Zealand > Phone: +64 3 3779127 Freecall: Australia 1800 148 751 > Fax: +64 3 3779135 USA 1800 261 2934 > -- > To unsubscribe from this list: send the line "unsubscribe kernel-janitors" in > the body of a message to majordomo at vger.kernel.org > More majordomo info at http://vger.kernel.org/majordomo-info.html >