linux-kernel - Re: [PATCH v2 11/14] power: supply: bq24190_charger: Get input_current

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Date:   Tue, 29 Aug 2017 13:53:24 +0200
From:   Hans de Goede <hdegoede@...hat.com>
To:     Sebastian Reichel <sebastian.reichel@...labora.co.uk>
Cc:     Wolfram Sang <wsa@...-dreams.de>,
        Guenter Roeck <linux@...ck-us.net>,
        Heikki Krogerus <heikki.krogerus@...ux.intel.com>,
        Darren Hart <dvhart@...radead.org>,
        Andy Shevchenko <andy@...radead.org>,
        Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        Liam Breck <liam@...workimprov.net>,
        Tony Lindgren <tony@...mide.com>, linux-i2c@...r.kernel.org,
        linux-pm@...r.kernel.org, platform-driver-x86@...r.kernel.org,
        linux-kernel@...r.kernel.org, devel@...verdev.osuosl.org
Subject: Re: [PATCH v2 11/14] power: supply: bq24190_charger: Get
 input_current_limit from our supplier

Hi,

Thank you for your reviews / queuing!

On 29-08-17 13:40, Sebastian Reichel wrote:
> Hi,
> 
> On Tue, Aug 15, 2017 at 10:04:59PM +0200, Hans de Goede wrote:
>> On some devices the USB Type-C port power (USB PD 2.0) negotiation is
>> done by a separate port-controller IC, while the current limit is
>> controlled through another (charger) IC.
>>
>> It has been decided to model this by modelling the external Type-C
>> power brick (adapter/charger) as a power-supply class device which
>> supplies the charger-IC, with its voltage-now and current-max representing
>> the negotiated voltage and max current draw.
>>
>> This commit adds support for this to the bq24190_charger driver by calling
>> power_supply_set_input_current_limit_from_supplier helper if the
>> "input-current-limit-from-supplier" device-property is set.
>>
>> Note this replaces the functionality to get the current-limit from an
>> extcon device, which will be removed in a follow-up commit.
> 
> I'm fine with the general approach, but ...
> 
>> [...]
>> +	bdi->input_current_limit_from_supplier =
>> +		device_property_read_bool(dev,
>> +					  "input-current-limit-from-supplier");
>> [...]
> 
> I wonder if we actually need this. I think we can just enable it
> unconditionally when we have a parent power supply providing the
> information.

I was thinking the same when implementing this, so this is fine with
me. I think it is best to just unconditionally call
power_supply_set_input_current_limit_from_supplier from the
external_power_changed callback, that will only get called if we've
a parent supply and that function will check that the parent has
a current-max property itself.

Please let me know if just unconditionally calling
power_supply_set_input_current_limit_from_supplier from the
external_power_changed callback is ok with you then I will do that
for v3 of the patch-set (from which I will drop the patches you've
already queued).

Regards,

Hans