linux-kernel - Re: [PATCH v3 1/2] iio: vadc: Qualcomm SPMI PMIC voltage ADC driver

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Date:	Sat, 04 Oct 2014 12:51:29 +0100
From:	Jonathan Cameron <jic23@...nel.org>
To:	"Ivan T. Ivanov" <iivanov@...sol.com>,
	Stanimir Varbanov <svarbanov@...sol.com>
CC:	lars <lars@...afoo.de>, sachin.kamat@...aro.org,
	srinivas.pandruvada@...ux.intel.com, linux-iio@...r.kernel.org,
	linux-arm-msm@...r.kernel.org, linux-kernel@...r.kernel.org,
	devicetree@...r.kernel.org
Subject: Re: [PATCH v3 1/2] iio: vadc: Qualcomm SPMI PMIC voltage ADC driver

On 02/10/14 13:08, Ivan T. Ivanov wrote:
> +iio maintainers
> 
> On Thu, 2014-10-02 at 12:29 +0300, Ivan T. Ivanov wrote:
>> Hi Stan,
>>
>> On 09/24/2014 03:56 PM, Stanimir Varbanov wrote:
>>
>> <snip>
>>
>>> +static int vadc_get_dt_data(struct vadc_priv *vadc, struct device_node *node)
>>> +{
>>> +	struct iio_chan_spec *iio_chan = vadc->iio_chans;
>>> +	const struct vadc_channels *vadc_chan;
>>> +	struct vadc_channel_prop prop;
>>> +	struct device_node *child;
>>> +	int ret, index = 0;
>>> +
>>> +	for_each_available_child_of_node(node, child) {
>>> +		ret = vadc_get_dt_channel_data(vadc->dev, &prop, child);
>>> +		if (ret)
>>> +			return ret;
>>> +
>>> +		vadc->chan_props[index] = prop;
>>> +
>>> +		vadc_chan = &vadc_chans[prop.channel];
>>> +
>>> +		iio_chan->channel = prop.channel;
>>> +		iio_chan->datasheet_name = vadc_chan->datasheet_name;
>>> +		iio_chan->info_mask_separate = vadc_chan->info_mask;
>>> +		iio_chan->type = vadc_chan->type;
>>> +		iio_chan->indexed = 1;
>>> +		iio_chan->scan_type.sign = 's';
>>> +		iio_chan->scan_type.realbits = 15;
>>> +		iio_chan->scan_type.storagebits = 16;
>>> +		iio_chan->address = index++;
>>> +
>>> +		iio_chan++;
>>> +	}
>>> +
>>> +	return 0;
>>> +}
>>> +
>>
>> <snip>
>>
>>> +static int vadc_probe(struct platform_device *pdev)
>>> +{
>>
>> <snip>
>>
>>> +
>>> +	indio_dev->dev.parent = dev;
>>> +	indio_dev->dev.of_node = node;
>>> +	indio_dev->name = pdev->name;
>>> +	indio_dev->modes = INDIO_DIRECT_MODE;
>>> +	indio_dev->info = &vadc_info;
>>> +	indio_dev->channels = vadc->iio_chans;
>>> +	indio_dev->num_channels = vadc->nchannels;
>>
>> This will not work as we thought. Registration will be fine and entries
>> in sysfs are created as expected, but this is breaking numbering scheme
>> for client drivers. For us the problem is that iio framework expect channels
>> numbering to be linear and channel number should not be greater than
>> channel count. For example even if die temperature channel is always 8, if
>> I describe only 5 channels in DTS files (4 for reference points measurement)
>> and 1 for die temperature, clients could not get OF reference to 
>> temperature
>> channel using io-channels = <&pm8941_vadc 8>;
>>
>> Jonathan, please, could you advise us.
I'd like to let the solution you proposed sit on the list a little longer.
It seems fairly sensible, but lets see what others suggest.

Jonathan
>>
>> Regards,
>> Ivan
>>
>>> +
>>> +	return devm_iio_device_register(dev, indio_dev);
>>> +}
>>> +
>>>
>>
>> --
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> 
> 
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