Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1754612AbaGKPe7 (ORCPT ); Fri, 11 Jul 2014 11:34:59 -0400 Received: from aserp1040.oracle.com ([141.146.126.69]:36725 "EHLO aserp1040.oracle.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1753421AbaGKPe5 (ORCPT ); Fri, 11 Jul 2014 11:34:57 -0400 Date: Fri, 11 Jul 2014 18:34:39 +0300 From: Dan Carpenter To: Ian Abbott Cc: linux-kernel@vger.kernel.org, kernel-janitors@vger.kernel.org, devel@driverdev.osuosl.org, gregkh@linuxfoundation.org, dcb314@hotmail.com Subject: Re: [PATCH v3] drivers/staging/comedi/drivers/ni_atmio16d.c: remove pointless condition Message-ID: <20140711153439.GD25880@mwanda> References: <1405089127-21646-1-git-send-email-abbotti@mev.co.uk> <1405089510-23182-1-git-send-email-abbotti@mev.co.uk> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <1405089510-23182-1-git-send-email-abbotti@mev.co.uk> User-Agent: Mutt/1.5.21 (2010-09-15) X-Source-IP: ucsinet21.oracle.com [156.151.31.93] Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Fri, Jul 11, 2014 at 03:38:30PM +0100, Ian Abbott wrote: > From: Andrey Utkin > > From: Andrey Utkin > > The issue was discovered with static analysis and has two instances in > this file. The code looks like this > if (x < 65536000) { > ... > } else if (x < 655360000) { > ... > } else if (x <= 0xffffffff /* 6553600000 */) { > ... > } else if (x <= 0xffffffff /* 65536000000 */) { > ... > } > > The meaning of this block is to select appropriate clock frequency for > interval timer basing on "x", which is amount of time. > > Notes: > 1. That last condition matches previous one - that's the issue. > 2. Decimal numbers in comments don't match hex numbers in expressions. > But in first case the numbers have same order, while in the second case > the hex number is the same, and the decimal one is 10 times bigger. > 3. Actually type of "x" is "unsigned int", so its exact upper limit is > not obviously known. > 4. There's no "else" block. > > So it makes sense to make an "else" block from last "else if" case. The > code inside the block seems correct for such usage. > > [ Actually, get rid of the final "else if" case and change the > next-to-last "else if" case to an "else" as the upper limit of "x" _is_ > known to be 0xffffffff (UINT_MAX), which is less than 6553600000 -- Ian ] > > Bugzilla: https://bugzilla.kernel.org/show_bug.cgi?id=79871 > Reported-by: David Binderman > Signed-off-by: Andrey Utkin > Signed-off-by: Ian Abbott > --- > v2: Removed final "else if" block and changed preceding "else if" block > to "else" block as the condition is always true due to limited range of > "unsigned int". -- Ian > v3: Corrected subject line I messed up in v2. -- Ian > --- > drivers/staging/comedi/drivers/ni_atmio16d.c | 10 ++-------- > 1 file changed, 2 insertions(+), 8 deletions(-) > > diff --git a/drivers/staging/comedi/drivers/ni_atmio16d.c b/drivers/staging/comedi/drivers/ni_atmio16d.c > index 6ad27f5..b1b4744 100644 > --- a/drivers/staging/comedi/drivers/ni_atmio16d.c > +++ b/drivers/staging/comedi/drivers/ni_atmio16d.c > @@ -335,12 +335,9 @@ static int atmio16d_ai_cmd(struct comedi_device *dev, > } else if (cmd->convert_arg < 655360000) { > base_clock = CLOCK_100_KHZ; > timer = cmd->convert_arg / 10000; > - } else if (cmd->convert_arg <= 0xffffffff /* 6553600000 */) { > + } else /* cmd->convert_arg < 6553600000 */ { I think the comment is meant to be /* cmd->convert_arg >= 655360000 */ There is an extra zero on 6553600000. The comment is obvious and should be removed. Or maybe I haven't understood the comment and in that case it is a useless sucky comment so we should delete it? regards, dan carpenter -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/