Re: adc-jack-driver opinion related to IIO

[Lars-Peter Clausen <lars@metafoo.de>]

On 07/10/2012 10:29 AM, anish singh wrote:
> On Fri, Jul 6, 2012 at 11:48 PM, Lars-Peter Clausen <lars@metafoo.de> wrote:
>> On 07/06/2012 06:45 PM, anish kumar wrote:
>>> On Fri, 2012-07-06 at 14:25 +0100, Jonathan Cameron wrote:
>>>> On 7/6/2012 1:00 PM, anish singh wrote:
>>>>> Hello Jonathan,
>>>>>
>>>>> I would be extremely happy if I can get your opinion on this.
>>>>>
>>>>> Recently Myungjoo Ham had posted Extcon: adc-jack driver patch.
>>>>>
>>>>> Description of this driver:
>>>>> This is basically a Headset(jack) driver.Once the headset is inserted
>>>>> a irq_handler is called and in this handler we have a callback(this
>>>>> callback calls into pmic driver to get the adc value) to get
>>>>> the adc value to determine the kind of headset: This headset could
>>>>> be headset with mic, headset without mic or headset with
>>>>> keys(volume-up/down) attached to it.One we have found out the kind
>>>>> of headset we use extcon framework to notify the other interested drivers or
>>>>> userspace that a headset with so and so capabilities has been inserted.
>>>>>
>>>>> Question:
>>>>> Does this driver fall into IIO as pointed by Mark Brown in his review comments?
>>>> The driver itself probably doesn't, but the adc part does in that IIO
>>>> provides a means of talking to the relevant adc.
>>>>>
>>>>> Why do we need to use IIO to get the adc value?As for different boards the
>>>>> method of getting adc is different.How does IIO help in this?
>>>> Ultimately, IIO in this case is acting as an infrastructure for ALL
>>>> adcs. E.g. for different boards you'll need a mapping to tell it which
>>>> adc channel is connected but that is it.  Hence you don't need a
>>>> specific callback for each pmic as you will be using generic interfaces
>>>> to query it.
>>> After having a brief glance at IIO below is my understanding:
>>> IIO is used to provide standard interfaces in the form of sysfs to
>>> userspace _ONLY_.
>>>
>>> My requirement:
>>> ADC-JACK-Driver should get the adc value from other driver i.e. PMIC
>>> driver.Here the requirement is communication between two drivers in
>>> kernel.Can IIO be used here?
>>>
>>> I had a look at drivers/staging/iio/Documentation/Overview.txt and some
>>> ADC drivers.
>>
>> Hi,
>>
>> There is a new experimental in kernel API, which lets you write IIO clients
>> in the kernel.
>>
>> See: drivers/iio/inkern.h
>> and drivers/staging/iio/iio_hwmon.c
> Thanks for this.So below is my understanding:
> 1.The driver which will provide adc value should first register itself with IIO
> core by specifiying it channels(struct iio_map should be used) and what
> values we can expect from it.
> 2.The driver which is interested in reading the adc values should call
> iio_channel_get
> to get the channel.
> 3.Once the channel is obtained we can call iio_st_read_channel_raw function to
> read the values.
> 
> Is my understanding right or I am completely lost here?

Yes, that sounds about right.

Btw. iio_st_read_channel_raw has been renamed to iio_read_channel_raw

- Lars