On Tue, 2013-08-13 at 22:23 +0100, Jonathan Cameron wrote: > On 07/22/13 15:04, Hector Palacios wrote: > > Some LRADC channels have fixed pre-dividers so they can measure > > different voltages at full scale. The reference voltage allows to > > expose a scaling attribute through the IIO sysfs so that a user can > > compute the real voltage out of a measured sample value. > > > > diff --git a/Documentation/devicetree/bindings/staging/iio/adc/mxs-lradc.txt b/Documentation/devicetree/bindings/staging/iio/adc/mxs-lradc.txt > > index 4688205..6ec485c 100644 > > --- a/Documentation/devicetree/bindings/staging/iio/adc/mxs-lradc.txt > > +++ b/Documentation/devicetree/bindings/staging/iio/adc/mxs-lradc.txt > > @@ -1,9 +1,12 @@ > > * Freescale i.MX28 LRADC device driver > > > > Required properties: > > -- compatible: Should be "fsl,imx28-lradc" > > +- compatible: "fsl,imx28-lradc", "fsl,imx23-lradc" > > - reg: Address and length of the register set for the device > > - interrupts: Should contain the LRADC interrupts > > +- fsl,vref: Reference voltage (in mV) for each LRADC channel. This is the > > + maximum voltage that can be measured at full scale in each channel > > + considering fixed pre-dividers. So, let me try to rephrase what I read above. There's an ADC with X channels. And there's a reference voltage source (one?). Now, each of the ADC channels have a (different?) voltage divider, taking the voltage from the reference source and feeding it to the ADC comparator. How much am I wrong? If I'm not wrong at all, I'd say that the reference source could be described as a standard fixed regulator (Documentation/devicetree/bindings/regulator/fixed-regulator.txt) and the ADC node should have some king of "reference-supply" phandle to the regulator node. Now, if the dividers factors are *really* fixed, the driver could know about them and calculate the effective reference voltage on its own, couldn't it? Let me repeat the "DT standard disclaimer": the tree, in general, should describe the way components are *wired up*, not much more. Pawel -- To unsubscribe from this list: send the line "unsubscribe linux-iio" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
