From mboxrd@z Thu Jan 1 00:00:00 1970 From: Brian Norris Subject: Re: [PATCH 2/2] HID: i2c-hid: support the regulator Date: Wed, 14 Sep 2016 16:02:42 +0800 Message-ID: <20160914080241.GA14576@localhost> References: <1473027116-13892-1-git-send-email-wxt@rock-chips.com> <1473027116-13892-2-git-send-email-wxt@rock-chips.com> <20160914073603.GH25951@mail.corp.redhat.com> <20160914075505.GA14271@localhost> Mime-Version: 1.0 Content-Type: text/plain; charset=us-ascii Return-path: Received: from mail-pf0-f171.google.com ([209.85.192.171]:33641 "EHLO mail-pf0-f171.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1755286AbcINICt (ORCPT ); Wed, 14 Sep 2016 04:02:49 -0400 Received: by mail-pf0-f171.google.com with SMTP id g202so3290213pfb.0 for ; Wed, 14 Sep 2016 01:02:48 -0700 (PDT) Content-Disposition: inline In-Reply-To: <20160914075505.GA14271@localhost> Sender: linux-input-owner@vger.kernel.org List-Id: linux-input@vger.kernel.org To: Benjamin Tissoires Cc: Caesar Wang , Jiri Kosina , linux-rockchip@lists.infradead.org, dbasehore@chromium.org, Douglas Anderson , Heiko Stuebner , linux-input@vger.kernel.org, Mika Westerberg , Dmitry Torokhov , Benson Leung , Guohua Zhong , "Zhonghui\"" , linux-kernel@vger.kernel.org On Wed, Sep 14, 2016 at 03:55:05PM +0800, Brian Norris wrote: > The default behavior of regulator_get() is to provide a dummy regulator > if none is found. So the pointer is never NULL, and it won't break > devices without a regulator. If you don't want a dummy regulator you > would use regulator_get_optional() instead, and you would then need to > handle ERR_PTR(-ENODEV) specifically. One caveat to the never-NULL comment above that I just noticed: If CONFIG_REGULATOR=n, then regulator_get() actually returns NULL (see include/linux/regulator/consumer.h), but it also specifically has a comment right next to that NULL return, saying: /* Nothing except the stubbed out regulator API should be * looking at the value except to check if it is an error * value. Drivers are free to handle NULL specifically by * skipping all regulator API calls, but they don't have to. * Drivers which don't, should make sure they properly handle * corner cases of the API, such as regulator_get_voltage() * returning 0. */ So, we still don't need to handle the NULL case specially. Brian