Re: [PATCH v2 5/5] iio: mxs-lradc: add write_raw function to modify scale

[Hector Palacios <hector.palacios@digi.com>]

Dear Marek,

On 07/19/2013 06:17 PM, Marek Vasut wrote:
>> Here you have three entries per channel:
>> in_voltageX_raw		-> the sample raw value
>> in_voltageX_scale	-> the scale to multiply the raw value to get the
> voltage
>> in mV in_voltageX_scale_available -> lists the available scales of the
>> channel
>>
>> For example for channel 0:
>>
>> # cat in_voltage0_scale_available
>> 0.451660156 0.903320312	(two scales available, first with divider by two
>> disabled, second with divider by two enabled)
>>
>> # cat in_voltage0_scale
>> 0.451660156			(divider by two is currently disabled)
>>
>> # cat in_voltage0_raw		(shows measured value)
>> 1000
>>
>> If you multiply the value by the scale you get: 1000 * 0.451660156 = 451.6
>> mV
>>
>> # echo 0.903320312 > in_voltage0_scale	(enables the divider by two)
>
> Ok, so I have to remember this value : '0.903320312' in case I want to enable
> divide-by-two functionality?

No you don't. That's why there is a 'in_voltage_scale_available' that lists the 
available values.

> Hmmmm ... why would this interface not work:
> echo 2 > in_voltage0_scale
>
> or
>
> echo 1 > in_voltage0_scale

An easy thing like that is what I first submitted, but it was rejected and I was told 
to use the scale_available descriptor instead, which is the common interface the rest 
of drivers use.

Best regards,
--
Hector Palacios