linux-kernel - Re: extending /sys/.../iio:deviceX/in_accelX_power

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Date:	Tue, 01 Mar 2016 11:07:21 +0100
From:	Martin Kepplinger <martink@...teo.de>
To:	Crt Mori <cmo@...exis.com>
Cc:	Daniel Baluta <daniel.baluta@...el.com>,
	Jonathan Cameron <jic23@...nel.org>,
	Lars-Peter Clausen <lars@...afoo.de>,
	Matt Ranostaj <mranostay@...il.com>,
	Haneen Mohammed <hamohammed.sa@...il.com>,
	Darshana Padmadas <darshanapadmadas@...il.com>,
	mfuzzey@...keon.com, octavian.purdila@...el.com,
	Irina Tirdea <irina.tirdea@...el.com>,
	Cristina Georgiana Opriceana <cristina.opriceana@...il.com>,
	Vladimir Barinov <vladimir.barinov@...entembedded.com>,
	linux-kernel@...r.kernel.org, linux-iio@...r.kernel.org
Subject: Re: extending /sys/.../iio:deviceX/in_accelX_power_mode

Am 01.03.2016 10:53 schrieb Crt Mori:
> On 1 March 2016 at 10:47, Martin Kepplinger <martink@...teo.de> wrote:
>> Am 2016-03-01 um 10:38 schrieb Daniel Baluta:
>>> On Tue, Mar 1, 2016 at 10:59 AM, Martin Kepplinger 
>>> <martink@...teo.de> wrote:
>>>> Would it be ok, if adding in_accelX_power_mode to a driver, to 
>>>> extend it
>>>> so that in_accel_power_mode_available offers:
>>>> 
>>>> low_noise low_power low_power_low_noise normal
>>>> 
>>>> if there's a default "normal" mode, plus options to increase or 
>>>> decrease
>>>> oversampling / power consumption for my device?
>>>> 
>>>> Specifically I'm unsure about "low_power_low_noise" being enough
>>>> user-friendly. The chip I work with just happens to offer these 4 
>>>> modes.
>>>> Would you leave out "low_power_low_noise" and go with
>>>> 
>>>> low_noise low_power normal
>>>> 
>>>> or is it not even desired to add "normal" to the list?
>>>> 
>>>> Although strictly not necessary, I would add any new addition to the
>>>> Documentation as well.
>>> 
>>> The problem with this is that is not uniform across sensors. What
>>> chip are you looking at?
>>> 
>>> For example INV6500 has:
>>> * sleep mode
>>> * standby mode
>>> * etc.
>>> 
>>> Daniel.
>>> 
>> 
>> I suspect these modes are something else. I'm looking at the mma8452
>> driver, and it also has "active" "standby" and "sleep" modes, but I'm
>> talking about different *power* (oversampling) configurations in
>> "active" mode, which is what said sysfs file is about.
>> 
>> But yes, it should be potenially uniform across sensors, which is why 
>> I
>> would probably only add "normal" to the list. At least I can imagine
>> that many devices have an oversampling mode called "normal".
> 
> If that is oversampling option then why don't you just use that as a
> setup? Power mode does not sound like oversampling to me... Maybe you
> should use a sampling_frequency parameter instead?
> 

well, it doesn't affect the sampling frequency. Oversampling is a way 
chips get
more accurate values and use more power. But it's fine. It comes down to
trying patches and see what happens anyways :)

>> 
>> A simple user interface is important so right now I think the best is 
>> to
>> leave it as it is, and not to add complexity and every possible option
>> for the user.
>> --
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