From: Lars-Peter Clausen <lars@metafoo.de>
To: Alexandre Belloni <alexandre.belloni@free-electrons.com>
Cc: Jonathan Cameron <jic23@kernel.org>,
Shawn Guo <shawn.guo@linaro.org>,
Grant Likely <grant.likely@secretlab.ca>,
jimwall@q.com, brian@crystalfontz.com,
Maxime Ripard <maxime.ripard@free-electrons.com>,
linux-iio@vger.kernel.org, linux-kernel@vger.kernel.org,
linux-doc@vger.kernel.org, linux-arm-kernel@lists.infradead.org,
devicetree-discuss@lists.ozlabs.org,
Jonathan Cameron <jic23@cam.ac.uk>, Rob Landley <rob@landley.net>,
Rob Herring <rob.herring@calxeda.com>
Subject: Re: [PATCHv2 1/3] iio: Add Nuvoton NAU7802 ADC driver
Date: Sun, 23 Jun 2013 15:54:08 +0200 [thread overview]
Message-ID: <51C6FE00.8010900@metafoo.de> (raw)
In-Reply-To: <51C5A68F.3000300@free-electrons.com>
On 06/22/2013 03:28 PM, Alexandre Belloni wrote:
> On 22/06/2013 15:20, Lars-Peter Clausen wrote:
>> On 06/22/2013 03:07 PM, Alexandre Belloni wrote:
>>> On 22/06/2013 14:02, Lars-Peter Clausen wrote:
>>>> On 06/22/2013 01:55 PM, Jonathan Cameron wrote:
>>>>> On 06/20/2013 07:57 PM, Alexandre Belloni wrote:
>>>>>> The Nuvoton NAU7802 ADC is a 24-bit 2-channels I2C ADC, with adjustable
>>>>>> gain and sampling rates.
>>>>>>
>>>>> Sorry, somewhat low on time today so only a quick review.
>>>>>
>>>>> 1) Missing userspace ABI documentation. Also, perhaps min_conversions is
>>>>> a little vague? Not that I have a better idea!
>>>> I really don't like the name min_conversions either. Isn't this effectively
>>>> a decimation filter?
>>> Yeah, it could be seen like that but it is only relevant and only
>>> happens when switching between channels. I'm open to any ideas.
>>>
>> I see. Is there anything about this in the datasheet on how many conversions
>> you usually need? Is this really something you need to change at runtime or
>> does moving this to platform data work?
>>
>>
>
> There is actually nothing in the datasheet. The default value (6
> conversions) was found experimentally. What I did was saturating the ADC
> with the higher value on one channel and the lower value on the other
> one and I tried to find when reading both channel sequentially was
> resulting in a correct value.
>
> You may not need to change it at runtime. And that value mainly depend
> on the precision versus speed balance you want to achieve. If you know
> that the values on both channels will not be to far apart, then you may
> not need to wait at all.
>
> Would you think that is something I should hide in the DT ? Or maybe I
> can drop that knob for now and see if it is needed in the future.
>
It is always a good idea to be conservative when introducing new ABI, so if
you think we can get away with hardcoding this in the driver I think that's
a good idea.
- Lars
next prev parent reply other threads:[~2013-06-23 13:54 UTC|newest]
Thread overview: 16+ messages / expand[flat|nested] mbox.gz Atom feed top
2013-06-20 18:57 [PATCHv2 0/3] Add support for the Nuvoton NAU7802 ADC to the cfa10049 Alexandre Belloni
2013-06-20 18:57 ` [PATCHv2 1/3] iio: Add Nuvoton NAU7802 ADC driver Alexandre Belloni
[not found] ` <1371754675-12242-2-git-send-email-alexandre.belloni-wi1+55ScJUtKEb57/3fJTNBPR1lH4CV8@public.gmane.org>
2013-06-22 11:55 ` Jonathan Cameron
[not found] ` <51C590B5.2060308-DgEjT+Ai2ygdnm+yROfE0A@public.gmane.org>
2013-06-22 12:02 ` Lars-Peter Clausen
[not found] ` <51C5923D.6030609-Qo5EllUWu/uELgA04lAiVw@public.gmane.org>
2013-06-22 13:07 ` Alexandre Belloni
2013-06-22 13:20 ` Lars-Peter Clausen
2013-06-22 13:28 ` Alexandre Belloni
2013-06-23 13:54 ` Lars-Peter Clausen [this message]
[not found] ` <51C6FE00.8010900-Qo5EllUWu/uELgA04lAiVw@public.gmane.org>
2013-06-23 17:33 ` Jonathan Cameron
2013-06-24 6:41 ` Lars-Peter Clausen
2013-06-24 10:37 ` Alexandre Belloni
[not found] ` <51C82169.1010203-wi1+55ScJUtKEb57/3fJTNBPR1lH4CV8@public.gmane.org>
2013-06-24 16:41 ` Lars-Peter Clausen
2013-06-24 17:26 ` Alexandre Belloni
2013-06-20 18:57 ` [PATCHv2 2/3] ARM: mxs: cfa10049: Switch bus i2c1 to bitbanging Alexandre Belloni
[not found] ` <1371754675-12242-3-git-send-email-alexandre.belloni-wi1+55ScJUtKEb57/3fJTNBPR1lH4CV8@public.gmane.org>
2013-06-21 22:27 ` Fabio Estevam
2013-06-20 18:57 ` [PATCHv2 3/3] ARM: mxs: cfa10049: Add NAU7802 ADCs to the device tree Alexandre Belloni
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