linux-kernel - Re: [PATCH v5 07/10] iio: adc: Support ROHM BD79124 ADC

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Message-ID: <a6fcc1af-5fb8-48bd-8ed8-6fb16b1a5d4c@gmail.com>
Date: Mon, 10 Mar 2025 10:46:45 +0200
From: Matti Vaittinen <mazziesaccount@...il.com>
To: Jonathan Cameron <jic23@...nel.org>
Cc: Matti Vaittinen <matti.vaittinen@...rohmeurope.com>,
 Lars-Peter Clausen <lars@...afoo.de>, Nuno Sa <nuno.sa@...log.com>,
 David Lechner <dlechner@...libre.com>,
 Javier Carrasco <javier.carrasco.cruz@...il.com>,
 Olivier Moysan <olivier.moysan@...s.st.com>,
 Guillaume Stols <gstols@...libre.com>,
 Dumitru Ceclan <mitrutzceclan@...il.com>,
 Trevor Gamblin <tgamblin@...libre.com>,
 Matteo Martelli <matteomartelli3@...il.com>,
 Alisa-Dariana Roman <alisadariana@...il.com>,
 Andy Shevchenko <andriy.shevchenko@...ux.intel.com>,
 João Paulo Gonçalves <joao.goncalves@...adex.com>,
 AngeloGioacchino Del Regno <angelogioacchino.delregno@...labora.com>,
 linux-kernel@...r.kernel.org, linux-iio@...r.kernel.org
Subject: Re: [PATCH v5 07/10] iio: adc: Support ROHM BD79124 ADC

On 08/03/2025 18:44, Jonathan Cameron wrote:
> On Mon, 3 Mar 2025 13:33:39 +0200
> Matti Vaittinen <mazziesaccount@...il.com> wrote:
> 
>> The ROHM BD79124 is a 12-bit, 8-channel, SAR ADC. The ADC supports
>> an automatic measurement mode, with an alarm interrupt for out-of-window
>> measurements. The window is configurable for each channel.
>>
>> The I2C protocol for manual start of the measurement and data reading is
>> somewhat peculiar. It requires the master to do clock stretching after
>> sending the I2C slave-address until the slave has captured the data.
>> Needless to say this is not well suopported by the I2C controllers.
>>
>> Thus the driver does not support the BD79124's manual measurement mode
>> but implements the measurements using automatic measurement mode relying
>> on the BD79124's ability of storing latest measurements into register.
>>
>> The driver does also support configuring the threshold events for
>> detecting the out-of-window events.
>>
>> The BD79124 keeps asserting IRQ for as long as the measured voltage is
>> out of the configured window. Thus the driver masks the received event
>> for a fixed duration (1 second) when an event is handled. This prevents
>> the user-space from choking on the events
>>
>> The ADC input pins can be also configured as general purpose outputs.
>> Those pins which don't have corresponding ADC channel node in the
>> device-tree will be controllable as GPO.
>>
>> Signed-off-by: Matti Vaittinen <mazziesaccount@...il.com>
> Hi Matti
> 
> Just a few really trivial comments.  If all else in the
> set was resolved I'd probably have applied with a tweak or two
> 
> Thanks,
> 
> Jonathan
> 
>>   obj-$(CONFIG_SC27XX_ADC) += sc27xx_adc.o
>> diff --git a/drivers/iio/adc/rohm-bd79124.c b/drivers/iio/adc/rohm-bd79124.c
>> new file mode 100644
>> index 000000000000..466c7decf8fc
>> --- /dev/null
>> +++ b/drivers/iio/adc/rohm-bd79124.c
>> @@ -0,0 +1,1108 @@
> ...
> 
>> +
>> +/* Read-only regs */
> 
> Given naming this is pretty obvious.
 > I would drop the comment

I will drop this, although I am not sure it is as self explatonary as 
one thinks. I've seen people getting this wrong because the logic of 
regmap-ranges is kind of reversed. (Eg, read-only is done by adding 
range to wr_tables and not to rd_tables - as a no-range).

Thanks for the review, and rest of the comments just agreed with.

-- Matti