From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1759514AbbA0TeH (ORCPT ); Tue, 27 Jan 2015 14:34:07 -0500 Received: from mail-ie0-f179.google.com ([209.85.223.179]:59052 "EHLO mail-ie0-f179.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751890AbbA0TeG (ORCPT ); Tue, 27 Jan 2015 14:34:06 -0500 Date: Tue, 27 Jan 2015 11:34:01 -0800 From: Dmitry Torokhov To: Priit Laes Cc: Maxime Ripard , linux-sunxi@googlegroups.com, Hans de Goede , linux-arm-kernel@lists.infradead.org, linux-kernel@vger.kernel.org, linux-input@vger.kernel.org Subject: Re: [linux-sunxi] Re: [PATCH] arm: sunxi: input: RFC: Add sysfs voltage for sun4i-lradc driver Message-ID: <20150127193401.GB29637@dtor-glaptop> References: <1422291516-24895-1-git-send-email-plaes@plaes.org> <20150127091829.GD7200@lukather> <1422352189.23189.12.camel@plaes.org> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <1422352189.23189.12.camel@plaes.org> User-Agent: Mutt/1.5.21 (2010-09-15) Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Tue, Jan 27, 2015 at 11:49:49AM +0200, Priit Laes wrote: > > On Tue, 2015-01-27 at 10:18 +0100, Maxime Ripard wrote: > > Hi, > > > > On Mon, Jan 26, 2015 at 06:58:32PM +0200, Priit Laes wrote: > > > --- > > > > Like Hans was pointing out, commit log and signed-off-by please > > > > > .../ABI/testing/sysfs-driver-input-sun4i-lradc | 4 ++ > > > drivers/input/keyboard/sun4i-lradc-keys.c | 49 > > > +++++++++++++++++----- > > > 2 files changed, 43 insertions(+), 10 deletions(-) > > > create mode 100644 Documentation/ABI/testing/sysfs-driver-input- > > > sun4i-lradc > > > > > > diff --git a/Documentation/ABI/testing/sysfs-driver-input-sun4i- > > > lradc b/Documentation/ABI/testing/sysfs-driver-input-sun4i-lradc > > > new file mode 100644 > > > index 0000000..e4e6448 > > > --- /dev/null > > > +++ b/Documentation/ABI/testing/sysfs-driver-input-sun4i-lradc > > > @@ -0,0 +1,4 @@ > > > +What: /sys/class/input/input(x)/device/voltage > > > +Date: February 2015 > > > +Contact: Priit Laes > > > +Description: ADC output voltage in microvolts or 0 if device is > > > not opened. > > > > Why is it returning 0 when "device is not opened" ? What does that > > even mean? You can't read that file without opening it. > > It means that something has to open the /dev/input/inputX device which > sets up the ADC before the voltage can be read from the sysfs file. I'd consider this a bug. Why someone has to use an unrelated interface for another interface to work correctly? > > [...] > > > > > > As I told you already, if you're going to expose this an ADC in the > > end, the proper solution is to use the IIO framework, not adding a > > custom sysfs file. > > My intention was to expose just a simple debug output, so one can > press the buttons and read the voltages for devicetree keymap. > > If anyone can suggest a simpler approach than current sysfs based one, > I would do it. But full blown iio driver is currently out of scope. > Also, Carlo's (ccaione) initially submitted (?) driver for lradc > utilized iio subsystem. For stuff like this debugfs (AKA dumping ground) is better suited as it does not establish ABI. i Thanks. -- Dmitry