From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S933493AbdBPVoA (ORCPT ); Thu, 16 Feb 2017 16:44:00 -0500 Received: from vern.gendns.com ([206.190.152.46]:39719 "EHLO vern.gendns.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S933087AbdBPVn6 (ORCPT ); Thu, 16 Feb 2017 16:43:58 -0500 Subject: Re: [PATCH v3 0/3] input: pwm-beeper: add feature to set volume level To: Frieder Schrempf , Dmitry Torokhov References: <0e2dec4d-7550-9495-f12a-020391183304@exceet.de> <20170119213700.GC13542@dtor-ws> <43679b65-8710-4255-2006-8c47dd755497@lechnology.com> Cc: robh@kernel.org, pawel.moll@arm.com, ijc+devicetree@hellion.org.uk, galak@codeaurora.org, luis@debethencourt.com, linux-input@vger.kernel.org, devicetree@vger.kernel.org, linux-kernel@vger.kernel.org From: David Lechner Message-ID: <5fc04e9d-7a92-2a34-e9cc-679106481e32@lechnology.com> Date: Thu, 16 Feb 2017 15:44:01 -0600 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:45.0) Gecko/20100101 Thunderbird/45.7.0 MIME-Version: 1.0 In-Reply-To: Content-Type: text/plain; charset=windows-1252; format=flowed Content-Transfer-Encoding: 7bit X-AntiAbuse: This header was added to track abuse, please include it with any abuse report X-AntiAbuse: Primary Hostname - vern.gendns.com X-AntiAbuse: Original Domain - vger.kernel.org X-AntiAbuse: Originator/Caller UID/GID - [47 12] / [47 12] X-AntiAbuse: Sender Address Domain - lechnology.com X-Get-Message-Sender-Via: vern.gendns.com: authenticated_id: davidmain+lechnology.com/only user confirmed/virtual account not confirmed X-Authenticated-Sender: vern.gendns.com: davidmain@lechnology.com X-Source: X-Source-Args: X-Source-Dir: Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On 02/16/2017 03:15 PM, Frieder Schrempf wrote: > Hello David, > > On 20.01.2017 20:11, David Lechner wrote: >> On 01/19/2017 03:37 PM, Dmitry Torokhov wrote: >>> On Thu, Jan 19, 2017 at 04:24:07PM +0100, Frieder Schrempf wrote: >>>> Make the driver accept switching volume levels via sysfs. >>>> This can be helpful if the beep/bell sound intensity needs >>>> to be adapted to the environment of the device. >>>> >>>> The number of volume levels available and their values can >>>> be specified via device tree (similar to pwm-backlight). >>>> >>>> The volume adjustment is done by changing the duty cycle of >>>> the pwm signal. >>> >>> I wonder how this all will mesh up with beepers that have dedicated >>> amplifiers (support is being added by David Lechner). >> >> This will work very well with it. I fact, it is a feature I would like >> to have but I was not sure about a good way to implement it. Please Cc: >> me on future revisions of this series and I will be glad to test it. > > I have just send v4. >> >> One thing that would be nice would be for a more generic way to change >> the volume from userspace. Having a sysfs attribute on the platform >> device will work, but it requires very specific knowledge from any >> userspace program that wants to control the volume. Would it be possible >> to add an alsa mixer volume control or something like that? > > An alsa mixer control for the pwm-beeper volume sounds nice, but > unfortunately I have no idea how one would implement this, or if this is > even possible. >> I know it is possible because I have done it. ;-) https://github.com/ev3dev/lego-linux-drivers/blob/master/evb/evb_sound.c The driver in the link above does PCM playback using PWM. But, it also included an input device similar to pwm-beeper and it includes an ALSA volume control specifically for the beeper.