From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1031439Ab2COBBx (ORCPT ); Wed, 14 Mar 2012 21:01:53 -0400 Received: from mprc.pku.edu.cn ([162.105.203.9]:42956 "EHLO mprc.pku.edu.cn" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S965275Ab2COBBv (ORCPT ); Wed, 14 Mar 2012 21:01:51 -0400 Message-ID: <1331773284.2389.61.camel@epip-laptop> Subject: Re: [PATCH 7/7] arch/unicore32/kernel/dma.c: ensure arguments to request_irq and free_irq are compatible From: Guan Xuetao Reply-To: gxt@mprc.pku.edu.cn To: Julia Lawall Cc: Dan Carpenter , kernel-janitors@vger.kernel.org, linux-kernel@vger.kernel.org Date: Thu, 15 Mar 2012 09:01:24 +0800 In-Reply-To: References: <1331494587-12196-1-git-send-email-Julia.Lawall@lip6.fr> <1331494587-12196-8-git-send-email-Julia.Lawall@lip6.fr> <1331513926.2048.58.camel@epip-laptop> <1331622633.2048.87.camel@epip-laptop> <1331712444.2389.36.camel@epip-laptop> <20120314081910.GC3163@mwanda> <1331714575.2389.47.camel@epip-laptop> Organization: MPRC, PKU Content-Type: text/plain; charset="UTF-8" X-Mailer: Evolution 3.2.2- Content-Transfer-Encoding: 7bit Mime-Version: 1.0 Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Wed, 2012-03-14 at 10:23 +0100, Julia Lawall wrote: > > On Wed, 14 Mar 2012, Guan Xuetao wrote: > > > On Wed, 2012-03-14 at 11:19 +0300, Dan Carpenter wrote: > >> On Wed, Mar 14, 2012 at 04:07:24PM +0800, Guan Xuetao wrote: > >>> puv3_init_dma() is called ONCE when initializing. > >>> In logical, if request_irq(IRQ_DMAERR, *) failed, free_irq(IRQ_DMA, *) > >>> is unnecessary, and dma device/driver can keep on working. > >>> The patch could be: > >>> ret = request_irq(IRQ_DMAERR, dma_err_handler, 0, "DMAERR", NULL); > >>> if (ret) { > >>> printk(KERN_CRIT "Can't register IRQ for DMAERR\n"); > >>> - free_irq(IRQ_DMA, "DMA"); > >>> return ret; > >>> } > >> > >> It seems like you should remove the error return as well? > >> > >> regards, > >> dan carpenter > >> > > The error return value will only generate an extra warning message, and > > have no side-effect. > > The whole thing seems a little strange. I guess your point is that the > call site never looks at the return value? Wouldn't it be better to make > there be no return value in that case? If there is a return value, some > calling context in the future might take that into account and then the > lack of a free_irq would be a memory leak. Also if the first request_irq > can never fail, perhaps that should be made explicit by not testing the > return value? > > julia This function is an init_call, not a probe function, and it is only called ONCE. The dma device here has two interrupts, one IRQ_DMA, another IRQ_DMAERR. And the device could work without IRQ_DMAERR. The return value should indicate whether there is something wrong during initialization, so the function needs return errno when any request_irq is failed. For the first request_irq, some code has prepared its resources before this call, so I suppose it successful. However, the return value must be tested. Regards, Guan Xuetao