Implement devicetree support for AB8500 Btemp

On Thursday 13 September 2012 08:07 PM, Arnd Bergmann wrote:

On Thursday 13 September 2012, Rajanikanth HV wrote:

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On Wednesday 12 September 2012 09:06 PM, 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?

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What does indeed seem to be needed is a place to identify the battery
type, but it's not clear if the btemp device is the best place for
that (maybe it is). 

I am not clear whether you are trying to correlate battery-type with
supplied-to. however, battery type is identified based on the
resistance value measured at batctrl pin which is expected to be in the
allowable limit of ab8500 device. This resistance limit varies across
battery types. This happens in btemp driver.

I wasn't correlating them. I just mentioned that unlike the supplied-to
property, the battery type property does seem to belong into the device
tree.

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For this, I would suggest you give a list of

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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.

If we expect the property to be needed only for ab8500, please use
a vendor prefix like 'stericsson,'.

it is fine to have battery-name in the battery-type property as said
above and to have binding document, the basic requirement is to
maintain the battery type information for a specified battery also
within the same technology of battery method, battery parameters may
vary. Presently battery-type and its dependent information is
maintained in the drivers/power/ folder as per the arnd review
sometimes back.

	Arnd