From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S964978AbWJJFFi (ORCPT ); Tue, 10 Oct 2006 01:05:38 -0400 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S964979AbWJJFFi (ORCPT ); Tue, 10 Oct 2006 01:05:38 -0400 Received: from mail.kroah.org ([69.55.234.183]:9698 "EHLO perch.kroah.org") by vger.kernel.org with ESMTP id S964978AbWJJFFh (ORCPT ); Tue, 10 Oct 2006 01:05:37 -0400 Date: Mon, 9 Oct 2006 22:04:53 -0700 From: Greg KH To: Andrew Morton Cc: Paul Mackerras , linux-kernel@vger.kernel.org Subject: Re: Why is device_create_file __must_check? Message-ID: <20061010050453.GA5479@kroah.com> References: <17707.8801.395100.35054@cargo.ozlabs.ibm.com> <20061009214936.a2788702.akpm@osdl.org> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20061009214936.a2788702.akpm@osdl.org> User-Agent: Mutt/1.5.13 (2006-08-11) Sender: linux-kernel-owner@vger.kernel.org X-Mailing-List: linux-kernel@vger.kernel.org On Mon, Oct 09, 2006 at 09:49:36PM -0700, Andrew Morton wrote: > On Tue, 10 Oct 2006 14:32:33 +1000 > Paul Mackerras wrote: > > > I am seeing a bunch of warnings about not checking the return value > > from device_create_file() for code like this (from > > arch/powerpc/kernel/pci_64.c): > > > > static ssize_t pci_show_devspec(struct device *dev, > > struct device_attribute *attr, char *buf) > > { > > struct pci_dev *pdev; > > struct device_node *np; > > > > pdev = to_pci_dev (dev); > > np = pci_device_to_OF_node(pdev); > > if (np == NULL || np->full_name == NULL) > > return 0; > > return sprintf(buf, "%s", np->full_name); > > } > > static DEVICE_ATTR(devspec, S_IRUGO, pci_show_devspec, NULL); > > > > void pcibios_add_platform_entries(struct pci_dev *pdev) > > { > > device_create_file(&pdev->dev, &dev_attr_devspec); > > } > > > > What bad thing could happen if device_create_file fails, other than > > that the "devspec" file doesn't appear in sysfs? > > There are no super-strong reasons here, but if device_create_file() fails > then the required control files aren't there and the subsystem isn't > working as intended. If it's in a module then we should fail the modprobe. > If it's a bootup thing then best we can do is to panic. Or at least log > the event. > > The most common cause of this is a programming error: we tried to create > the same entry twice. We want to know about that. Exactly, that's the most common cause here (different programmers trying to create the same file in the same place.) That needs to error out so that it is caught properly. thanks, greg k-h