From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1755766Ab3A1NQo (ORCPT ); Mon, 28 Jan 2013 08:16:44 -0500 Received: from moutng.kundenserver.de ([212.227.126.171]:59554 "EHLO moutng.kundenserver.de" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1754091Ab3A1NQk (ORCPT ); Mon, 28 Jan 2013 08:16:40 -0500 Date: Mon, 28 Jan 2013 14:16:23 +0100 From: Thierry Reding To: Florian Vaussard Cc: Peter Ujfalusi , Bryan Wu , Richard Purdie , linux-leds@vger.kernel.org, linux-arm-kernel@lists.infradead.org, linux-kernel@vger.kernel.org Subject: Re: [PATCH v2 1/3] pwm: Add pwm_cansleep() as exported API to users Message-ID: <20130128131622.GA1783@avionic-0098.mockup.avionic-design.de> References: <1359121471-21457-1-git-send-email-florian.vaussard@epfl.ch> <1359121471-21457-2-git-send-email-florian.vaussard@epfl.ch> <20130126054024.GB29243@avionic-0098.adnet.avionic-design.de> <51063AB5.2060108@ti.com> <51064687.5090605@epfl.ch> <20130128095754.GA23134@avionic-0098.adnet.avionic-design.de> <510659A3.7070906@epfl.ch> MIME-Version: 1.0 Content-Type: multipart/signed; micalg=pgp-sha1; protocol="application/pgp-signature"; boundary="ew6BAiZeqk4r7MaW" Content-Disposition: inline In-Reply-To: <510659A3.7070906@epfl.ch> User-Agent: Mutt/1.5.21 (2010-09-15) X-Provags-ID: V02:K0:YGripHckq90BQMnsIeDlynUDorYztPf7B3Jq9WSEO+r VVQt1Wi5zKegE4B6e8aPFTnX6ILUDl9VoHnAX/X9gwXBlVFbTE /Srjx3GODTVTGO90CuoCadNGASM+eTIbrVRF3bRfaC9dErjOc4 nyITzAu2TDWDID9w7XX2JebOsErB5oWWZ0LUJAtPhpLHDb56sU hCBKASYlul1xXMEBm+ufn/Wyzin811bQRj0rWuJa3wFGqhVjP/ /krI7NgwLa8SSh9l9suZvtz/61nO2mbeQH04X1op5O28P0suvE hkkHF6VzP90eI0B8Js8OI7XHofaLSR1E8MDFgJ0RDVFH5M3Ce0 YVJgHgFfRGYeu7qpdrjd2r7kKG059fzln+oygmafRwIUsLqzyz OL0M0Yf6bZTu+2iOuEcUjI988wrIrcp9vA= Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org --ew6BAiZeqk4r7MaW Content-Type: text/plain; charset=utf-8 Content-Disposition: inline Content-Transfer-Encoding: quoted-printable On Mon, Jan 28, 2013 at 11:57:39AM +0100, Florian Vaussard wrote: > Le 28/01/2013 10:57, Thierry Reding a =C3=A9crit : > >On Mon, Jan 28, 2013 at 10:36:07AM +0100, Florian Vaussard wrote: > >>Hello, > >> > >>Le 28/01/2013 09:45, Peter Ujfalusi a =C3=A9crit : > >>>hi Thierry, > >>> > >>>On 01/26/2013 06:40 AM, Thierry Reding wrote: > >[...] > >>>>>+{ > >>>>>+ return pwm->chip->can_sleep; > >>>>>+} > >>>>>+EXPORT_SYMBOL_GPL(pwm_cansleep); > >>>> > >>>>Would it make sense to check for NULL pointers here? I guess that > >>>>passing NULL into the function could be considered a programming error > >>>>and an oops would be okay, but in that case there's no point in making > >>>>the function return an int. Also see my next comment. > >>> > >>>While it is unlikely to happen it is better to be safe, something like= this > >>>will do: > >>> > >>>return pwm ? pwm->chip->can_sleep : 0; > >>> > >> > >>Ok. And what about: > >> > >>BUG_ON(pwm =3D=3D NULL); > >>return pwm->chip->can_sleep; > > > >I don't think we need that. In case pwm =3D=3D NULL, dereferencing it wi= ll > >oops anyway. So either we make it safe and return an error code, or we > >let it oops without explicit BUG_ON(). > > >=20 > Calling this function with a NULL pointer is a programming error, so there > is no error codes for such errors. You could return -EINVAL if pwm =3D=3D NULL. > I propose to return bool, and let it oops if such case happens. My point was that it will oops even if you don't use BUG_ON() so there isn't so much point in using it explicitly. Thierry --ew6BAiZeqk4r7MaW Content-Type: application/pgp-signature -----BEGIN PGP SIGNATURE----- Version: GnuPG v2.0.19 (GNU/Linux) iQIcBAEBAgAGBQJRBnomAAoJEN0jrNd/PrOhjSwP/3mkZ2hcCdvoWIsotAFpKheD GiC9vhXwgfcNKefZvbE9x8k55iRGnfeJwW5/vf3wJvuvVsb8EJeBBj5yj5UiBl0K KO5KuloAuQ3qfKoVyRkTstsK1tg7SJml0EL/SFCS/k4R997z9llU8dN4ZUgS/R4/ /2Hc0ja+HCbQBF3CXl4ILqGymg2cbXjmnsbyRzm8tGZEg2QKvb0xzOvnAD5yysXc luJMWJJYBoG5HI+qSvVrRWrhmPiJNaEjfAONu3E9HiyJXSxHOmy5BIi6jPmDi5Td dxNeX77qhCmRm6X966cCnG0DO7iywPPgp8xYAI+p4jeRvSv7b+GUd859Lhh8hbhL EfGelGQmzFoelZYf1XQ1V3EOpPMjGvp4/hY/Pv3d6e4K+r94xiNcIdB2FndhEsQ/ YkD5zYdLS4rhiIkOC+wt/PVbMWTgzkkdNWahHs+z4VhqMyhnu1YPLZd2aOKoZ7he 5cB7aCWC7HoMxS1tJqxJz3vqPcB4JaZdRZN98hvLid48z/THfW3xUyLvPqU5SMgy ooXrp8rOixu2DC980fbw3p0ltr0A+hNU6nVh5HSrbFhLr3JBhGrK/KwmIRyAwzYM ayVDI8CKVlqbjcnpA4wX8AazWGhKaQpnGZ8eJbzA0sJSTuxmF/OYbYI3U5s+yof2 zgcU9OhTW4V7iEIl/cmT =t3/6 -----END PGP SIGNATURE----- --ew6BAiZeqk4r7MaW--