Re: [PATCH]staging:iio:ad799x make use of platform_data optional

[Jonathan Cameron <jic23@kernel.org>]

On 01/01/14 13:17, Hartmut Knaack wrote:
> Jonathan Cameron schrieb:
>> On 29/12/13 11:49, Hartmut Knaack wrote:
>>> Setting Vref with platform_data is a neat feature, though it is
>>> not essential for operating these devices. So make the use of
>>> platform_data optional and set default value of 1000 mV if
>>> nothing else is defined.
>>>
>>> Signed-off-by: Hartmut Knaack <knaack.h@gmx.de>
>> Hi Hartmut,
> Hi
>>
>> Why a default of 1V?  Does that correspond to anything in
>> particular?
> This makes it easier to calculate your real voltage, since you only
> need to multiply with your reference voltage. Another reason: if you
> are more interested in the relation of your input in the range
> [0V-Vref], you can simply get the per mill value.
Sorry, but I'm not going to take this as whilst I can see how it
is useful for your use case, it would introduce a new non standard
interface.
>>
>> Whilst the way this is set here is clunky there is a need for this
>> voltage to be supplied in some fashion.  Now we'd do it via a
>> regulator to give us nice standard device tree bindings and to
>> allow for less simplistic hardware configurations.
>>
>> So lets say we convert this to use a regulator, is there still a
>> reason why one might want a default value?
> I'm not aware of the current state of the device tree implementation
> at the moment. My intention is to also be able to use this driver
> without the need of compiling a custom kernel (so to use the
> distribution of choice out of the box).
Then it needs to be device tree enabled and the configuration done
via that.

Jonathan
>>> ---
>>> diff --git a/drivers/staging/iio/adc/ad799x_core.c b/drivers/staging/iio/adc/ad799x_core.c
>>> index 9428be8..e32a555 100644
>>> --- a/drivers/staging/iio/adc/ad799x_core.c
>>> +++ b/drivers/staging/iio/adc/ad799x_core.c
>>> @@ -545,10 +545,12 @@ static int ad799x_probe(struct i2c_client *client,
>>>
>>>    	/* TODO: Add pdata options for filtering and bit delay */
>>>
>>> -	if (!pdata)
>>> -		return -EINVAL;
>>> -
>>> -	st->int_vref_mv = pdata->vref_mv;
>>> +	if ((!pdata) || (!pdata->vref_mv)) {
>>> +		dev_warn(&client->dev,
>>> +			 "No platform data found, setting Vref to 1000 mV\n");
>>> +		st->int_vref_mv = 1000;
>>> +	} else
>>> +		st->int_vref_mv = pdata->vref_mv;
>>>
>>>    	st->reg = devm_regulator_get(&client->dev, "vcc");
>>>    	if (!IS_ERR(st->reg)) {
>>> --
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