linux-kernel - Re: [PATCH v3 2/5] iio: sensorhub: Add sensorhub bindings

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Message-ID: <549D549C.1000803@kernel.org>
Date:	Fri, 26 Dec 2014 12:29:16 +0000
From:	Jonathan Cameron <jic23@...nel.org>
To:	Karol Wrona <k.wrona@...sung.com>, linux-iio@...r.kernel.org,
	Hartmut Knaack <knaack.h@....de>, linux-kernel@...r.kernel.org
CC:	Bartlomiej Zolnierkiewicz <b.zolnierkie@...sung.com>,
	Kyungmin Park <kyungmin.park@...sung.com>,
	Karol Wrona <wrona.vy@...il.com>,
	"devicetree@...r.kernel.org" <devicetree@...r.kernel.org>,
	Rob Herring <robh+dt@...nel.org>,
	Pawel Moll <pawel.moll@....com>,
	Mark Rutland <mark.rutland@....com>,
	Ian Campbell <ijc+devicetree@...lion.org.uk>,
	Kumar Gala <galak@...eaurora.org>
Subject: Re: [PATCH v3 2/5] iio: sensorhub: Add sensorhub bindings

On 16/12/14 07:30, Karol Wrona wrote:
> On 12/06/2014 03:29 PM, Jonathan Cameron wrote:
>> On 05/12/14 19:54, Karol Wrona wrote:
>>> Add sensorhub bindings for sensorhub on Galaxy Gear 2.
>>>
>>> Change-Id: I4ee25aef33c21a4662de230841de9a8684f2c26b
>>> Signed-off-by: Karol Wrona <k.wrona@...sung.com>
>>> Acked-by: Kyungmin Park <kyungmin.park@...sung.com>
>> Looks good to me.  Comments inline.  Note I either need a device tree
>> ack or a long delay before I can take this though.  Unlikely to get the
>> device tree ack as you haven't cc'd the maintainers or list ;)
> I am curious about DT community opinion and I prefer to know it before
> v4 sending.
They have a lot of patches to review, so might take a while ;)
> 
>>
>> I've added the cc's. Please make sure future versions have them or you'll
>> just be slowing the process down (particularly if no one notices they 
>> are missing!)
> Thanks, I will remember that.
>>
>>> ---
>>>  .../devicetree/bindings/iio/sensorhub.txt          |   46 ++++++++++++++++++++
>>>  1 file changed, 46 insertions(+)
>>>  create mode 100644 Documentation/devicetree/bindings/iio/sensorhub.txt
>>>
>>> diff --git a/Documentation/devicetree/bindings/iio/sensorhub.txt b/Documentation/devicetree/bindings/iio/sensorhub.txt
>>> new file mode 100644
>>> index 0000000..2aca0c3
>>> --- /dev/null
>>> +++ b/Documentation/devicetree/bindings/iio/sensorhub.txt
>>> @@ -0,0 +1,46 @@
>>> +Samsung Sensorhub driver
>>> +
>>> +Sensorhub is a MCU which manages several sensors and also plays the role
>>> +of a virtual sensor device.
>>> +
>>> +Required properties:
>>> +- compatible: "samsung,sensorhub-rinato" or "samsung,sensorhub-thermostat"
>>> +- spi-max-frequency: max SPI clock frequency
>>> +- interrupt-parent: interrupt parent
>>> +- interrupts: communication interrupt
>>> +- ap-mcu-gpio: [out] ap to sensorhub line - used during communication
>>> +- mcu-ap-gpio: [in] sensorhub to ap - used during communication
>>> +- mcu-reset: [out] sensorhub reset
>> as commented in previous patch, why do the first two have -gpio and the
>> third not?
> Ok, all 3 will have "gpios" ending
>>> +
>>> +Optional properties:
>>> +- sensor's nodes:
>>> +  compatible = "samsung,mpu6500-accel"
>>> +  compatible = "samsung,mpu6500-gyro"
>>> +  compatible = "samsung,adpd142"
>>> +
>>> +Sensor compatibles are used to match proper sensor driver to real sensor on
>>> +the board. The firmware does not give such information, so it helps to specify
>>> +some sensors properties. Sensors have "samsung" prefixes because frequently
>>> +they will not have much in common with sensors used without sensorhub because
>>> +it can do some data processing.
>> We'll keep that under review.  Might make sense, sometimes, to unify the
>> drivers.  The different compatible will probably still be needed, but if
>> these devices proliferate I don't want two drivers for everything that
>> gets stuck behind them.
> I think that sensorhub is very similar hid-sensor (without hotpluging) where
> every sensor type has its own representation.  The real sensors are not driven
> directly but by external MCU so very often these sensors will not have much
> common with real ones.  So I wonder if it could be better to resign from these
> sensor compatibles and represent each sensor as mfd cell so optional properties
> probably will dropped (?)
Might do.
> Generally I intended to have i.e. one ssp-accel driver if they use another
> accelerometer then mpu6500 the buffering manner and sysfs will be handled in the
> same way.  I think I was mistaken with these compatibles.  There is also some
> probability that the firmware will be fixed someday and it will be able to tell
> more about sensor then the type.
Would be good - particularly if we start to get lots of variants out in the wild.
> 
>>> +
>>> +Example:
>>> +
>>> +	shub_spi: shub {
>>> +		compatible = "samsung,sensorhub-rinato";
>>> +		spi-max-frequency = <5000000>;
>>> +		interrupt-parent = <&gpx0>;
>>> +		interrupts = <2 0>;
>>> +		ap-mcu-gpio = <&gpx0 0 0>;
>>> +		mcu-ap-gpio = <&gpx0 4 0>;
>>> +		mcu-reset = <&gpx0 5 0>;
>>> +		sensor@0 {
>>> +			compatible = "samsung,mpu6500-accel";
>>> +		};
>>> +		sensor@1 {
>>> +			compatible = "samsung,mpu6500-gyro";
>>> +		};
>>> +		sensor@2 {
>>> +			compatible = "samsung,adpd142";
>>> +		};
>>> +	};
>>>
>>
>>
> 

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