linux-kernel - Re: [PATCH] IIO AD7923 iio

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Message-ID: <524FDD4F.7080406@metafoo.de>
Date:	Sat, 05 Oct 2013 11:35:11 +0200
From:	Lars-Peter Clausen <lars@...afoo.de>
To:	leroy christophe <christophe.leroy@....fr>
CC:	Jonathan Cameron <jic23@....ac.uk>, linux-kernel@...r.kernel.org,
	linux-iio@...r.kernel.org, patrick.vasseur@....fr
Subject: Re: [PATCH] IIO AD7923 iio_consumer support

On 10/05/2013 11:18 AM, leroy christophe wrote:
> 
> Le 05/10/2013 10:41, Lars-Peter Clausen a écrit :
>> On 10/05/2013 10:21 AM, Christophe Leroy wrote:
>>> +        .consumer_channel = "channel_0",
>>> +        .adc_channel_label = "0",
>>> +    },
>>> +    {
>>> +        .consumer_dev_name = AD7923_NAME,
>>> +        .consumer_channel = "channel_1",
>>> +        .adc_channel_label = "1",
>>> +    },
>>> +    {
>>> +        .consumer_dev_name = AD7923_NAME,
>>> +        .consumer_channel = "channel_2",
>>> +        .adc_channel_label = "2",
>>> +    },
>>> +    {
>>> +        .consumer_dev_name = AD7923_NAME,
>>> +        .consumer_channel = "channel_3",
>>> +        .adc_channel_label = "3",
>>> +    },
>>> +    { }
>>> +};
>> This is a mapping between channel names of the provider between the channel
>> names of the consumer. So it is specific to a certain combination of
>> consumer and provider and usually depend on how things are physically wired
>> on your board. As such there can be no generic mapping and this needs to go
>> into your machine/board driver. The mapping is usually passed to the IIO
>> driver via its platform data.
>>
>> So e.g. imagine you have a provider like this driver and you have a consumer
>> that has a "voltage" channel. And on your board channel 3 of the ADC is what
>> you want to route to that consumer. Then your mapping would look like this:
>>
>> {
>>     .consumer_dev_name = "your_consumer_device.1",
>>     .consumer_channel = "voltage",
>>     .adc_channel_label = "AIN3",
>> }
>>
>> And in your consumer driver you'd do:
>>
>> channel = iio_channel_get(dev, "voltage");
>>
>>
> Thanks for the explanation.
> 
> Can the mapping be retrieved via of_platform ?
> 
> Indeed, the only exemple I found was in the lp8788_adc driver, which
> includes iio/machine.h and declares a default mapping, but it is based on
> platform_data, not of_platform.
>

If you are using device tree you can specify the mapping inside the
devicetree. Have a look at
Documentation/devicetree/bindings/iio/iio-bindings.txt

- Lars

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