From: Rob Herring <robh@kernel.org>
To: Schrempf Frieder <frieder.schrempf@exceet.de>
Cc: "dmitry.torokhov@gmail.com" <dmitry.torokhov@gmail.com>,
"pawel.moll@arm.com" <pawel.moll@arm.com>,
"ijc+devicetree@hellion.org.uk" <ijc+devicetree@hellion.org.uk>,
"galak@codeaurora.org" <galak@codeaurora.org>,
"luis@debethencourt.com" <luis@debethencourt.com>,
"linux-input@vger.kernel.org" <linux-input@vger.kernel.org>,
"devicetree@vger.kernel.org" <devicetree@vger.kernel.org>,
"linux-kernel@vger.kernel.org" <linux-kernel@vger.kernel.org>
Subject: Re: [PATCH v2 2/3] input: pwm-beeper: add documentation for volume devicetree bindings
Date: Tue, 11 Oct 2016 08:39:57 -0500 [thread overview]
Message-ID: <CAL_JsqLGY+6eWb4dN-TMmt+PJSK6zm6gPgO3SCPa4esSpTzW8w@mail.gmail.com> (raw)
In-Reply-To: <24e35d49-7c3d-b094-f0b7-96367389f249@exceet.de>
On Tue, Oct 11, 2016 at 3:17 AM, Schrempf Frieder
<frieder.schrempf@exceet.de> wrote:
> On 10.10.2016 17:20, Rob Herring wrote:
>> On Fri, Oct 07, 2016 at 09:08:17AM +0000, Schrempf Frieder wrote:
>>> This patch adds the documentation for the devicetree bindings to set
>>> the volume levels.
>>>
>>> Signed-off-by: Frieder Schrempf <frieder.schrempf@exceet.de>
>>> ---
>>> Changes in v2:
>>> - split into 3 separate patches
>>> - make volume properties optional
>>>
>>> .../devicetree/bindings/input/pwm-beeper.txt | 22 ++++++++++++++++++++++
>>> 1 file changed, 22 insertions(+)
>>>
>>> diff --git a/Documentation/devicetree/bindings/input/pwm-beeper.txt b/Documentation/devicetree/bindings/input/pwm-beeper.txt
>>> index be332ae..6d8ba4e 100644
>>> --- a/Documentation/devicetree/bindings/input/pwm-beeper.txt
>>> +++ b/Documentation/devicetree/bindings/input/pwm-beeper.txt
>>> @@ -5,3 +5,25 @@ Registers a PWM device as beeper.
>>> Required properties:
>>> - compatible: should be "pwm-beeper"
>>> - pwms: phandle to the physical PWM device
>>> +
>>> +Optional properties:
>>> +- volume-levels: Array of distinct volume levels. These need to be in the
>>> + range of 0 to 500, while 0 means 0% duty cycle (mute) and 500 means
>>> + 50% duty cycle (max volume).
>>> + Please note that the actual volume of most beepers is highly
>>> + non-linear, which means that low volume levels are probably somewhere
>>> + in the range of 1 to 30 (0.1-3% duty cycle).
>>
>> What does the index correspond to? The linear volume?
>
> In most cases users probably need linear volume levels (e.g. 0%, 25%,
> 50%, 75%, 100%) and in this case the index would indeed correspond to
> the linear perceived volume.
>
> But also non-linear relations are possible (e.g. 0%, 20%, 100%), if the
> user needs for example "mute", "low", "high" as volume levels.
Exclude off/mute and this is still linear. Also, the user exposed
levels could be a subset of the defined h/w levels. That should be
independent of DT.
> The linearization (defining the corresponding duty cycle for each index)
> depends on the beeper and the perception of the user.
This has to be a consistent interface across h/w to have a userspace
that can work across h/w. For that, you have to define the binding as
linear. Of course, it's all measured by perception and not completely
accurate which is fine.
> For the example array definition below, I tried different duty cycles
> and found values of 0.8%, 2%, 4%, 50% to be approximately correspondent
> to perceived volume levels of 25%, 50%, 75%, 100% in my case.
>
>>
>>> +- default-volume-level: the default volume level (index into the
>>> + array defined by the "volume-levels" property)
>>> +
>>> +The volume level can be set via sysfs under /sys/class/input/inputX/volume.
>>> +The maximum volume level index can be read from /sys/class/input/inputX/max_volume_level.
Also, drop this. Not relevant to the binding.
Rob
next prev parent reply other threads:[~2016-10-11 13:40 UTC|newest]
Thread overview: 35+ messages / expand[flat|nested] mbox.gz Atom feed top
2016-04-07 15:58 [PATCH 1/1] input: pwm-beeper: add feature to set volume via sysfs Schrempf Frieder
2016-04-11 15:21 ` Rob Herring
2016-10-07 9:00 ` Schrempf Frieder
2016-10-07 9:08 ` [PATCH v2 0/3] input: pwm-beeper: add feature to set volume level Schrempf Frieder
2016-10-07 9:08 ` [PATCH v2 1/3] input: pwm-beeper: add feature to set volume via sysfs Schrempf Frieder
2016-10-07 9:08 ` [PATCH v2 2/3] input: pwm-beeper: add documentation for volume devicetree bindings Schrempf Frieder
2016-10-10 15:20 ` Rob Herring
2016-10-11 8:17 ` Schrempf Frieder
2016-10-11 13:39 ` Rob Herring [this message]
2017-01-19 14:40 ` Frieder Schrempf
2017-01-19 15:24 ` [PATCH v3 0/3] input: pwm-beeper: add feature to set volume level Frieder Schrempf
2017-01-19 15:24 ` [PATCH v3 1/3] input: pwm-beeper: add feature to set volume via sysfs Frieder Schrempf
2017-01-19 21:29 ` Dmitry Torokhov
2017-02-16 20:37 ` Frieder Schrempf
2017-01-19 15:24 ` [PATCH v3 2/3] input: pwm-beeper: add documentation for volume devicetree bindings Frieder Schrempf
2017-01-23 14:40 ` Rob Herring
2017-01-19 15:24 ` [PATCH v3 3/3] input: pwm-beeper: add devicetree bindings to set volume levels Frieder Schrempf
2017-01-19 21:30 ` Dmitry Torokhov
2017-02-16 20:40 ` Frieder Schrempf
2017-01-19 21:37 ` [PATCH v3 0/3] input: pwm-beeper: add feature to set volume level Dmitry Torokhov
2017-01-20 19:11 ` David Lechner
2017-02-16 21:15 ` Frieder Schrempf
2017-02-16 21:44 ` David Lechner
2017-02-17 10:01 ` Frieder Schrempf
2017-02-16 21:08 ` [PATCH v4 " Frieder Schrempf
2017-02-16 21:08 ` [PATCH v4 1/3] input: pwm-beeper: add feature to set volume via sysfs Frieder Schrempf
2017-02-16 21:08 ` [PATCH v4 2/3] input: pwm-beeper: add documentation for volume devicetree bindings Frieder Schrempf
2017-02-16 21:08 ` [PATCH v4 3/3] input: pwm-beeper: add devicetree bindings to set volume levels Frieder Schrempf
2017-02-16 23:07 ` kbuild test robot
2017-02-17 0:14 ` kbuild test robot
2017-02-17 9:54 ` [PATCH v5 0/3] input: pwm-beeper: add feature to set volume level Frieder Schrempf
2017-02-17 9:54 ` [PATCH v5 1/3] input: pwm-beeper: add feature to set volume via sysfs Frieder Schrempf
2017-02-17 9:54 ` [PATCH v5 2/3] input: pwm-beeper: add documentation for volume devicetree bindings Frieder Schrempf
2017-02-17 9:54 ` [PATCH v5 3/3] input: pwm-beeper: add devicetree bindings to set volume levels Frieder Schrempf
2016-10-07 9:08 ` [PATCH v2 " Schrempf Frieder
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