linux-kernel - Re: [PATCH] Input: pwm-beeper: support customized freq for SND

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Date:   Mon, 13 Feb 2017 20:27:48 -0800
From:   Dmitry Torokhov <dmitry.torokhov@...il.com>
To:     "Jonas Mark (ST-FIR/ENG1)" <Mark.Jonas@...bosch.com>
Cc:     Heiko Schocher <hs@...x.de>,
        "linux-input@...r.kernel.org" <linux-input@...r.kernel.org>,
        "GUAN Ben (ST-FIR/ENG1-Zhu)" <Ben.Guan@...bosch.com>,
        "devicetree@...r.kernel.org" <devicetree@...r.kernel.org>,
        Thierry Reding <thierry.reding@...il.com>,
        "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
        Boris Brezillon <boris.brezillon@...e-electrons.com>,
        Rob Herring <robh+dt@...nel.org>,
        Manfred Schlaegl <manfred.schlaegl@....at>,
        Mark Rutland <mark.rutland@....com>
Subject: Re: [PATCH] Input: pwm-beeper: support customized freq for SND_BELL

On Wed, Feb 08, 2017 at 10:11:21AM +0000, Jonas Mark (ST-FIR/ENG1) wrote:
> Hello Dmitry,
> 
> > > extend the pwm-beeper driver to support customized frequency
> > > for SND_BELL from device tree.
> > 
> > No, SND_BELL is literally SND_TONE @1000Hz. There should be no
> > customizing. If applications want to use different frequency then should
> > be using SND_TONE.
> 
> We are not aiming for an application shortcut here. Instead, changing
> the bell frequency shall be a system setting. That is, every
> application which wants to make a bell sound shall use the alternative
> frequency.
> 
> The reason why we are deviating from the default 1000 Hz is that on
> our hardware we are using a loudspeaker which is rated for 2.7 kHz.
> That is, it will only sound at the specified volume and frequency if
> you feed it with a 2.7 kHz square wave. If you deviate from it, e.g.
> by using 1000 Hz, the output will be dim and squeaky. Worst case,
> SND_BELL would be completely silent on our system. So the only bell
> sound we can reliably generate on our system has 2.7 kHz.

OK, fair enough. Please address Rob's comments on binding and resend.

Also I am not sure why you needed to change the switch statement around,
you only need to replace 1000 with value from the attribute.

Oh, and please use device_property_*() API instead of of_*().

Thanks.

-- 
Dmitry