linux-kernel - Re: [PATCH 1/1] iio: adc: Add driver for the TI INA3221 Triple Current/Voltage Monitor

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Date:	Mon, 11 Apr 2016 11:47:44 -0500
From:	"Andrew F. Davis" <afd@...com>
To:	Guenter Roeck <linux@...ck-us.net>
CC:	Jonathan Cameron <jic23@...nel.org>,
	Hartmut Knaack <knaack.h@....de>,
	Lars-Peter Clausen <lars@...afoo.de>,
	Peter Meerwald <pmeerw@...erw.net>,
	Marc Titinger <mtitinger@...libre.com>,
	<linux-iio@...r.kernel.org>, <linux-kernel@...r.kernel.org>,
	Jean Delvare <jdelvare@...e.de>, <linux-hwmon@...r.kernel.org>
Subject: Re: [PATCH 1/1] iio: adc: Add driver for the TI INA3221 Triple
 Current/Voltage Monitor

On 04/11/2016 11:38 AM, Guenter Roeck wrote:
> On Mon, Apr 11, 2016 at 10:48:27AM -0500, Andrew F. Davis wrote:
>> On 04/10/2016 06:57 AM, Jonathan Cameron wrote:
>>> On 08/04/16 19:19, Andrew F. Davis wrote:
>>>> The INA3221 is a three-channel, high-side current and bus voltage monitor
>>>> with an I2C and SMBUS compatible interface.
>>>>
>>>> Signed-off-by: Andrew F. Davis <afd@...com>
>>> Hi Andrew,
>>>
>>> My immediate thought on this one is whether it would be better off in hwmon.
>>> I'm not convinced either way from a quick glance at the data sheet, but the
>>> question needs to be addressed.
>>>
>>
>> I was on the fence with this also, I was leaning towards hwmod until I
>> looked onto how the ina2xx driver has been ported to iio. This is almost
>> the same part but the ina3x has three monitors vs one. In addition it
>> looks like NVIDIA has written a hwmod driver for this part
>> (https://github.com/Bogdacutu/STLinux-Kernel/blob/master/drivers/hwmon/ina3221.c)
>> but then also ported it over to IIO (although doesn't appear to be
>> upstream ready or ever has been submitted for such)
>> (https://github.com/SuperPichu/shield-tablet-kernel/blob/master/drivers/staging/iio/meter/ina3221.c)
>> So I figured this was the way things are moving, but I have no problem
>> working this as a hwmod driver. The IIO work is already done here, I'll
>> write the hwmod version also but keep working this, I see no reason we
>> cant have both if needed. (unless using this and just using iio_hwmod.c
>> if needed is more acceptable?)
>>
> 
> You can not have both since they would conflict with each other.
> ina2xx has possibly created a bad precedent. I am not inclined to accept
> a hwmon driver if an iio driver already exists. If you want an iio driver,
> fine with me, but then you (and its users) will have to live with its
> limitations when it comes to hardware monitoring.
> 

Hmm, my plan was an MFD device core, that then could mediate the two
sub-drivers, but I'm not sure about this yet.

> I don't really mind if things are going all towards iio if that is where
> the community wants to go. However, if that is the case, I would suggest
> that someone should spend the time to define a clear sense of 'limits'
> as well as alert handling in iio, in a way that is exportable to other
> subsystems (hwmon and thermal come into mind).
> 

I agree. I think both frameworks offer useful interfaces, so I would
hate to limit users to one, but for now I'll just post the hwmon version
here in a bit and live with that until someone requests the IIO support.

Andrew