From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1758035Ab3BXPLo (ORCPT ); Sun, 24 Feb 2013 10:11:44 -0500 Received: from gloria.sntech.de ([95.129.55.99]:36160 "EHLO gloria.sntech.de" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1757164Ab3BXPLm (ORCPT ); Sun, 24 Feb 2013 10:11:42 -0500 From: Heiko =?iso-8859-1?q?St=FCbner?= To: Julia Lawall Subject: Re: question about arch/arm/mach-s3c24xx/irq.c Date: Sun, 24 Feb 2013 16:11:12 +0100 User-Agent: KMail/1.13.7 (Linux/3.2.0-3-686-pae; KDE/4.8.4; i686; ; ) Cc: "Russell King - ARM Linux" , ben-linux@fluff.org, kgene.kim@samsung.com, linux-arm-kernel@lists.infradead.org, linux-samsung-soc@vger.kernel.org, linux-kernel@vger.kernel.org References: <20130224123849.GH17833@n2100.arm.linux.org.uk> In-Reply-To: MIME-Version: 1.0 Content-Type: Text/Plain; charset="iso-8859-1" Content-Transfer-Encoding: 7bit Message-Id: <201302241611.13028.heiko@sntech.de> Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Am Sonntag, 24. Februar 2013, 14:39:45 schrieb Julia Lawall: > [Adding the person who introduced the code] > > On Sun, 24 Feb 2013, Russell King - ARM Linux wrote: > > On Sun, Feb 24, 2013 at 12:45:11PM +0100, Julia Lawall wrote: > > > The function s3c24xx_irq_map in arch/arm/mach-s3c24xx/irq.c contains > > > the > > > > > > code: > > > parent_irq_data = > > > &parent_intc->irqs[irq_data->parent_irq]; > > > > > > if (!irq_data) { > > > > > > pr_err("irq-s3c24xx: no irq data found for > > > hwirq %lu\n", > > > > > > hw); > > > > > > goto err; > > > > > > } > > > > > > At this point irq_data has already been tested, so the null test on > > > irq_data does not look correct. But I wonder if parent_irq_data could > > > ever be null here? > > > > That would be really obscure - because that would require parent_intc to > > be a "negative" pointer (to counter-act the indexing by > > irq_data->parent_irq). So it looks to me like the above is redundant. > > Even at its original definition irq_data seems unlikely to be NULL: > > struct s3c_irq_intc *intc = h->host_data; > struct s3c_irq_data *irq_data = &intc->irqs[hw]; > ... > if (!irq_data) { > pr_err("irq-s3c24xx: no irq data found for hwirq %lu\n", > hw); return -EINVAL; > } > > That is, it could be an invalid value, but whether it actually hits 0 > would seem to depend on the value hw? > > Heiko, is NULL really a possibility? The test you quoted is of course wrong ... it would need to test parent_irq_data. But you're also right that the test is not necessary at all. All the s3c_irq_data arrays used always contain 32 entries to reach all bits of the register (which is used differently on each SoC). So if we have found the parent_intc at all, it should contain a 32 entries array of irq_data structs, so no need to test for the existence of the individual array element. And now that I look at it, I also see another glitch. The code tests for parent_irq != 0, which of course won't work if the parent_irq is the 0-hwirq of the parent controller. The only SoC using such a mapping is the s3c2412 [0], which explains why I haven't been bitten by this myself. Heiko [0] http://www.mail-archive.com/linux-samsung- soc@vger.kernel.org/msg15709.html