From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1752839Ab1AXVGL (ORCPT ); Mon, 24 Jan 2011 16:06:11 -0500 Received: from mail.bluewatersys.com ([202.124.120.130]:23182 "EHLO hayes.bluewaternz.com" rhost-flags-OK-OK-OK-FAIL) by vger.kernel.org with ESMTP id S1752486Ab1AXVGK (ORCPT ); Mon, 24 Jan 2011 16:06:10 -0500 Message-ID: <4D3DE9CD.2040800@bluewatersys.com> Date: Tue, 25 Jan 2011 10:06:21 +1300 From: Ryan Mallon User-Agent: Mozilla/5.0 (X11; U; Linux i686; en-US; rv:1.9.2.13) Gecko/20101208 Lightning/1.0b2 Thunderbird/3.1.7 MIME-Version: 1.0 To: Julia Lawall 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 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: X-Enigmail-Version: 1.1.2 Content-Type: text/plain; charset=ISO-8859-1 Content-Transfer-Encoding: 7bit Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On 01/25/2011 10:01 AM, Julia Lawall wrote: > 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? I think that users are expected to ensure that clock names and clock function names do not overlap. ~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