Re: power_supply: Making "enum power_supply_type type" dynamic

[Sebastian Reichel <sre@kernel.org>]

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Hi,

On Thu, Jul 02, 2015 at 05:56:17PM +0000, Pallala, Ramakrishna wrote:
> Currently 'enum power_supply_type type' is part of 'struct
> power_supply_desc' which is again defined as a 'const *' in
> 'struct power_supply'
> 
> Can we move the 'enum power_supply_type type' to 'struct
> power_supply' itself?
> 
> Rational behind this is, if you take any mobile or tablet device
> it comes with one USB charging port but it can support multiple
> charging cables like SDP, CDP and DCP etc.. So whenever we connect
> any of these cables we need to adjust the charger parameters
> accordingly.
>
> So the point here is, If we are using same physical charging port
> and the same charger IC for setting up the charging we can have
> one power supply class registration from the charger driver and
> change the power supply type based on the cable detection at
> runtime.
> 
> The current implementation forces us to create multiple power
> supply objects for each cable type which is not optimal as all
> these objects set/get methods operate on the same set of
> registers.

Sounds legit. I would prefer not to modify all existing drivers, though.
Instead of 'moving' the type field I suggest the following strategy:

struct power_supply_desc {
    ...
    enum power_supply_type type;
    ...
}

struct power_supply {
    ...
    enum power_supply_type type;
    ...
}

struct power_supply * power_supply_register(...) {
    ...
    psy.type = psy_desc.type;
    ...
}

This way chargers with static type, batteries, ... do not have
to be changed at all and runtime changeable chargers have a
nice default value.

-- Sebastian

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