From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1751894Ab2GSQcf (ORCPT ); Thu, 19 Jul 2012 12:32:35 -0400 Received: from acsinet15.oracle.com ([141.146.126.227]:42501 "EHLO acsinet15.oracle.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751300Ab2GSQcd (ORCPT ); Thu, 19 Jul 2012 12:32:33 -0400 Date: Thu, 19 Jul 2012 19:32:11 +0300 From: Dan Carpenter To: H Hartley Sweeten Cc: Ian Abbott , "devel@driverdev.osuosl.org" , "gregkh@linuxfoundation.org" , Ian Abbott , Linux Kernel Subject: Re: [PATCH 01/90] staging: comedi: comedidev.h: introduce comedi_to_pci_dev() helper Message-ID: <20120719163211.GD16291@mwanda> References: <201207181824.15722.hartleys@visionengravers.com> <5007D1E0.4050503@mev.co.uk> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: User-Agent: Mutt/1.5.21 (2010-09-15) X-Source-IP: ucsinet22.oracle.com [156.151.31.94] Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Thu, Jul 19, 2012 at 11:20:52AM -0500, H Hartley Sweeten wrote: > On Thursday, July 19, 2012 2:23 AM, Ian Abbott wrote: > > On 2012-07-19 02:24, H Hartley Sweeten wrote: > >> Introduce a wrapper for to_pci_dev() to allow the comedi pci drivers > >> to store the pci_dev pointer in the comedi_device hw_dev variable and > >> retrieve it easily. > >> > >> Signed-off-by: H Hartley Sweeten > >> Cc: Ian Abbott > >> Cc: Greg Kroah-Hartman > >> --- > >> drivers/staging/comedi/comedidev.h | 5 +++++ > >> 1 file changed, 5 insertions(+) > >> > >> diff --git a/drivers/staging/comedi/comedidev.h b/drivers/staging/comedi/comedidev.h > >> index de8c99c..620222d 100644 > >> --- a/drivers/staging/comedi/comedidev.h > >> +++ b/drivers/staging/comedi/comedidev.h > >> @@ -446,6 +446,11 @@ static inline void comedi_set_hw_dev(struct comedi_device *dev, > >> } > >> } > >> > >> +static inline struct pci_dev *comedi_to_pci_dev(struct comedi_device *dev) > >> +{ > >> + return to_pci_dev(dev->hw_dev); > >> +} > >> + > > > > That needs to be something like: > > > > return dev->hw_dev ? to_pci_dev(dev->hw_dev) : NULL; > > Hmm.. I'm not really sure. > > I assumed that the container_of() macro would return NULL if the ptr passed to > it was NULL. But, I'm not sure how this actually unwinds for that case. > > Greg, do you know if the NULL check is needed? It's is possible that the dev->hw_dev > pointer could be NULL. > container_of() just does pointer math with the offset. Since ->hw_dev is not the first member of the pci_dev struct then to_pci_dev() never returns NULL. If you give it a NULL pointer it returns a bogus pointer back. regards, dan carpenter