On 24 January 2013 15:24, Lars-Peter Clausen <lars@xxxxxxxxxx> wrote:
>
> On 01/24/2013 01:42 AM, Doug Anderson wrote:
> > Lars,
> >
> > On Wed, Jan 23, 2013 at 4:52 AM, Lars-Peter Clausen <lars@xxxxxxxxxx> wrote:
> >>> Few doubts regarding the mappings and child device handling.
> >>> Kindly, suggest me better methods.
> >>
> >> The patch looks mostly good now. As for the mappings, the problem is that we
> >> currently do not have any device tree bindings for IIO. So a proper solution
> >> would be to add dt bindings for IIO.
> >
> > Can you explain more how you think this would work? It seems like
> > just having child nodes as platform drivers would be OK (to me) and
> > having them instantiated with of_platform_populate() seems reasonable.
> >
> > ...but the one thing that is missing is a way for children to get
> > access to the channel properly.
> >
> > The children have access to the ADC "struct device" (it is their
> > parent device) and have a channel number (their "reg" field), but
> > there is no API call to map this to a "struct iio_channel". Is that
> > all that's needed in this case? ...or are you envisioning something
> > more?
>
> Well, the idea is that the consumer doesn't need to know the channel number.
> That's what the mapping takes care of. It basically creates a consumer alias
> for the channel. When requesting the channel the consumer always uses the
> same name.
>
> iio_channel_get(dev_name(&pdev->dev), "voltage");
>
> And the mapping contains an entry which maps the tuple of device name and
> channel name to a real IIO channel which as been registered by a IIO device.
> Note if there is only one channel you can also just use NULL for the channel
> name. This is similar to how clocks are managed with the clk framework.
>
> Now for the dt bindings I think we should stick to something similar to what
> the clk framework does.
>
> E.g.
>
> adc: adc@12D10000 {
>
> #io-channel-cells = <1>;
> io-channel-output-names = "adc1", "adc2", ...;
>
> ncp15wb473@0 {
> compatible = "ntc,ncp15wb473";
> ...
> io-channels = <&adc 0>; // First ADC channel
> io-channel-names = "voltage";
> };
>
> ncp15wb473@0 {
> compatible = "ntc,ncp15wb473";
> ...
> io-channels = <&adc 1>; // Second ADC channel
> io-channel-names = "voltage";
> }
> };
>
Hello Lars,
I've a doubt here
How do i find the child dev_name for iio_map_array_register();
cause the child devices are probed during of_platform_populate();
and during the probe the child calls
iio_channel_get(dev_name(&pdev->dev), "voltage");
The child device nodes are ncp15wb473.0 and ncp15wb473.1 in this case.
But, this may change.
Kindly, help.
Assume we have a device tree like this
adc@12D10000 {
#io-channel-cells = <1>;
io-channel-output-names = "adc0", "adc1", "adc2",
"adc3", "adc4", "adc5",
"adc6", "adc7", "adc8", "adc9";
ncp15wb473@0 {
compatible = "ntc,ncp15wb473";
reg = <0x0>;
io-channel-names = "voltage";
pullup-uV = <1800000>;
pullup-ohm = <47000>;
pulldown-ohm = <0>;
};
ncp15wb473@1 {
compatible = "ntc,ncp15wb473";
reg = <0x1>;
io-channel-names = "voltage";
pullup-uV = <1800000>;
pullup-ohm = <47000>;
pulldown-ohm = <0>;
};
};
> io-channel-output-names and io-channel-names can be optional. In the case
> where there is only one channel it's not really necessary to use
> io-channel-names.
>
> - Lars
--
Shine bright,
(: Nav :)
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