From mboxrd@z Thu Jan 1 00:00:00 1970 From: Ian Abbott Date: Fri, 11 Jul 2014 12:01:03 +0000 Subject: Re: [PATCH] drivers/staging/comedi/drivers/ni_atmio16d.c: remove pointless condition Message-Id: <53BFD1FF.20309@mev.co.uk> List-Id: References: <1405073603-21468-1-git-send-email-andrey.krieger.utkin@gmail.com> In-Reply-To: <1405073603-21468-1-git-send-email-andrey.krieger.utkin@gmail.com> MIME-Version: 1.0 Content-Type: text/plain; charset="us-ascii" Content-Transfer-Encoding: 7bit To: Andrey Utkin , linux-kernel@vger.kernel.org, kernel-janitors@vger.kernel.org, devel@driverdev.osuosl.org Cc: gregkh@linuxfoundation.org, hsweeten@visionengravers.com, dcb314@hotmail.com On 2014-07-11 11:13, Andrey Utkin wrote: > 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. > > Bugzilla: https://bugzilla.kernel.org/show_bug.cgi?idy871 > Reported-by: David Binderman > Signed-off-by: Andrey Utkin > --- > drivers/staging/comedi/drivers/ni_atmio16d.c | 4 ++-- > 1 file changed, 2 insertions(+), 2 deletions(-) > > diff --git a/drivers/staging/comedi/drivers/ni_atmio16d.c b/drivers/staging/comedi/drivers/ni_atmio16d.c > index 6ad27f5..895b56d 100644 > --- a/drivers/staging/comedi/drivers/ni_atmio16d.c > +++ b/drivers/staging/comedi/drivers/ni_atmio16d.c > @@ -338,7 +338,7 @@ static int atmio16d_ai_cmd(struct comedi_device *dev, > } else if (cmd->convert_arg <= 0xffffffff /* 6553600000 */) { > base_clock = CLOCK_10_KHZ; > timer = cmd->convert_arg / 100000; > - } else if (cmd->convert_arg <= 0xffffffff /* 65536000000 */) { > + } else { > base_clock = CLOCK_1_KHZ; > timer = cmd->convert_arg / 1000000; > } Since 0xffffffff is the maximum value 'cmd->convert_arg' can be, the final else can be moved to the 'base_clock = CLOCK_10_KHZ' block and the 'base_clock = CLOCK_1_KHZ' block can be removed altogether. > @@ -406,7 +406,7 @@ static int atmio16d_ai_cmd(struct comedi_device *dev, > } else if (cmd->scan_begin_arg < 0xffffffff /* 6553600000 */) { > base_clock = CLOCK_10_KHZ; > timer = cmd->scan_begin_arg / 100000; > - } else if (cmd->scan_begin_arg < 0xffffffff /* 65536000000 */) { > + } else { > base_clock = CLOCK_1_KHZ; > timer = cmd->scan_begin_arg / 1000000; > } > Same here as well for 'cmd->scan_begin_arg'. (And I think the original code should have used '<= 0xffffffff' rather than '< 0xffffffff'.) -- -=( Ian Abbott @ MEV Ltd. E-mail: )=- -=( Tel: +44 (0)161 477 1898 FAX: +44 (0)161 718 3587 )=-