Implement devicetree support for AB8500 Btemp

(Thanks for Cc'ing me.)

On Thu, Sep 13, 2012 at 02:37:38PM +0000, Arnd Bergmann wrote:
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If this is true, I don't understand what makes the 'supplied-to'
properties you list in the device tree binding board specific. Are
they not always done the same way? If so, you could just leave them
out.

Precisely 'supplied-to' is not board specific, it was maintained as
platform_data which i migrated to dt-node. It is meant to establish
dependency across bm drivers based on power_supply property and
runtime battery attributes.
Basically, 'supplied-to' provides a way of exporting change in
power_supply_property and runtime batter characteristics so that other
bm devs shall make use or refer the updated values.
Ref: external_power_changed(...) call back api.
Note: all the bm drivers handles subset of power_supply property and
      battery attributes,
      ref: include/linux/power_supply.h and get_property(...) call back
      api across bm drivers.

Ok, so you want to just remove the property from the device tree,
or do you want to establish a different method to specify these
connections?

Power supply subsystem's supplied_to describes not just how driver
should notify other devices, supplied_to is more generic stuff, in terms
that it describes power supply hierarchy. It's like a directed graph,
e.g.:

      <AC power> supplied_to <main battery> and <backup battery>
     <USB power> supplied_to <main battery> and <backup battery>
  <main battery> supplied_to <system>
<backup battery> supplied_to <system>
  <cmos battery> supplied_to <southbridge pci device>
  <mice battery> supplied_to <mice wireless hid>

How things interact in linux are just implementations details.
So, device tree is surely a perfect place to describe these things.

Although, in current bindings I see this:

+       ab8500-fg {
+               /* Other enery management module */
+               supplied_to = "ab8500_chargalg", "ab8500_usb";
+               num_supplicants = <2>;
+       };

Instead of addressing supplicants by name, it's better to address
via phandles. And, of course, num_supplicants is not needed, it can
be derived.

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possible batteries and require a property such as

 st-ericsson,battery-type: A string identifier for the type of battery,
			   which impacts how an operating system interpret
			   the sensor readings. Possible values include:
	* "none"	-- no battery connected
	* "li-ion-9100" -- Type 9100 Li-ION battery
	* <add any others that apply here>

Can do this, not precisely as "st-ericsson,battery-type", it will be as
battery-type = [unknown|NiMH|LION|...|]], reason being
allowable battery type is based on technology, as you can see the
possible types as:
POWER_SUPPLY_TECHNOLOGY_UNKNOWN = 0,
        POWER_SUPPLY_TECHNOLOGY_NiMH,
        POWER_SUPPLY_TECHNOLOGY_LION,
        POWER_SUPPLY_TECHNOLOGY_LIPO,
        POWER_SUPPLY_TECHNOLOGY_LiFe,
        POWER_SUPPLY_TECHNOLOGY_NiCd,
        POWER_SUPPLY_TECHNOLOGY_LiMn
Ref: include/linux/power_supply.h
Note: doing this will impact my of_probe(...), may slightly bloat the
code.

Ok.

If you want to make the battery type a generic property, it's probably
best to start a separate binding document for this in
Documentation/devicetree/bindings/power-supply/common.txt
and document a string for each of these.

Fully agree. We need to document generic DT bindings for power supplies.

Thanks,
Anton.