From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1752880Ab1AXVcF (ORCPT ); Mon, 24 Jan 2011 16:32:05 -0500 Received: from mgw2.diku.dk ([130.225.96.92]:54763 "EHLO mgw2.diku.dk" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751811Ab1AXVcC (ORCPT ); Mon, 24 Jan 2011 16:32:02 -0500 Date: Mon, 24 Jan 2011 22:31:57 +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: <4D3DE9CD.2040800@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> <4D3DE9CD.2040800@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 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. One can't have a clock with a different name but the same device and function? julia