From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1754793AbcHVIoI (ORCPT ); Mon, 22 Aug 2016 04:44:08 -0400 Received: from mout.kundenserver.de ([212.227.17.10]:53361 "EHLO mout.kundenserver.de" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1752152AbcHVInP (ORCPT ); Mon, 22 Aug 2016 04:43:15 -0400 From: Arnd Bergmann To: linux-arm-kernel@lists.infradead.org Cc: Christophe JAILLET , linux@prisktech.co.nz, gregkh@linuxfoundation.org, jslaby@suse.com, kernel-janitors@vger.kernel.org, linux-serial@vger.kernel.org, linux-kernel@vger.kernel.org Subject: Re: [PATCH] serial: vt8500_serial: Fix a parameter of find_first_zero_bit. Date: Mon, 22 Aug 2016 10:42:28 +0200 Message-ID: <2512469.eM8MYFl15l@wuerfel> User-Agent: KMail/5.1.3 (Linux/4.4.0-31-generic; KDE/5.18.0; x86_64; ; ) In-Reply-To: <1471814425-18949-1-git-send-email-christophe.jaillet@wanadoo.fr> References: <1471814425-18949-1-git-send-email-christophe.jaillet@wanadoo.fr> MIME-Version: 1.0 Content-Transfer-Encoding: 7Bit Content-Type: text/plain; charset="us-ascii" X-Provags-ID: V03:K0:S/x9mo/TrQmN0TVz62jdCOOYjV7Vp4oug4TYgVyLsCu5kCzWZWn NsovPumZ/a3AM80WrP5ojiJqYC8Z2KpldMTJhicHo1secToJZqllUuKsdVDVKgMmf6P054c PUM+xBQkp+kVQ4KnXaJAJAjYpFwVlGkrNhULYom46AxN6Qwaccj3pWhCkyx7+PBnCG1d9EF Lb0syIhz3jZWs5Z5DRIuw== X-UI-Out-Filterresults: notjunk:1;V01:K0:b4YPMY85y7E=:VyUgC9RTtYWBlBWD3oC4mQ pXjg+uojfDjPWlya6s8QQ2mGPLPRvmoDmENJq/PKWtGYYdSTz85s5eXzbVzuw3I5qxiLzqv2P TIfEHINk8ZFMw6muH7pdPSaC2HfTkVZy9PFP6C2/0Nf0Aqwba/UyUpIC1veb4JavkftT+QbTx WUpgQ8p2hqE/uTUjLTghE+i+rNzWbXndiiIoCiP7G000U4ck8Zz5/iw2slkoJIEifDGWnuUDW pez21uSrqgNY8zyjLnuX8Hr5MhhIcRyuEDE0upsox9jW7rD9iBrkNg/rKzK2TCEFNdr3yMYkC 3ey7awaa7RjWurwt9iNyogBM2FHGZrrVNzGaF3VE4d6tqeC+wH6kdvzBbYrn415Zc/9ai3b92 LS8uyYbA95kaXzddCY5nfQgReZ5T++LQlnlQBWvnxEqjt9SJPxp4mPI4UcAXjia/z4fr0hbI2 ykjmLru/IJ3GfsYN6zWkTWZHuJHf1xmPVTXswmOpUk0vN2lf1Th/8tHMJRbHW6KKu0ZX4CfUY 3ISWLFfP/Cu4Qj9uF2qRYFHVMJFspnXLEz8IqcBDCa8EayPtp5SKUEAOMaDaqOmqrlFyjj8ZY Jthsi4/I6L9iyKW3GW/6y4ws2IT7XzkK0hANREXbHvdEM8yXcSXcsY7UsuXluE533u+g5WUAu bh52bkCq/gpQ89RnssjhVUtAEJS0gFqxGOFpyssj1yn1Kss6tNEK0pc+n/ZTYXADhRnRIc4pW odQDFZX41aYL8i6i Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Sunday, August 21, 2016 11:20:25 PM CEST Christophe JAILLET wrote: > The 2nd parameter of 'find_first_zero_bit' is the number of bits to search. > In this case, we are passing 'sizeof(vt8500_ports_in_use)'. > 'vt8500_ports_in_use' is an 'unsigned long'. So the sizeof is likely to > return 4. > > A few lines below, we check if it is below VT8500_MAX_PORTS, which is 6. > > It is likely that the number of bits in a long was expected here, so use > BITS_PER_LONG instead. > > > It has been spotted by the following coccinelle script: > @@ > expression ret, x; > > @@ > * ret = \(find_first_bit \| find_first_zero_bit\) (x, sizeof(...)); > > Signed-off-by: Christophe JAILLET > --- > Other options are possible: > - 'vt8500_ports_in_use' being a 'unsigned long', use ffz to reduce > code verbosity > - VT8500_MAX_PORTS, in order to be consistent with the test below Sorry, but I'm not following the logic here. > --- > drivers/tty/serial/vt8500_serial.c | 2 +- > 1 file changed, 1 insertion(+), 1 deletion(-) > > diff --git a/drivers/tty/serial/vt8500_serial.c b/drivers/tty/serial/vt8500_serial.c > index 23cfc5e16b45..935076c50cb1 100644 > --- a/drivers/tty/serial/vt8500_serial.c > +++ b/drivers/tty/serial/vt8500_serial.c > @@ -664,7 +664,7 @@ static int vt8500_serial_probe(struct platform_device *pdev) > if (port < 0) { > /* calculate the port id */ > port = find_first_zero_bit(&vt8500_ports_in_use, > - sizeof(vt8500_ports_in_use)); > + BITS_PER_LONG); > } You argue that the two have the same meaning, which I see, but why is it better than the existing code? Arnd