linux-kernel - Re: [PATCH v4 01/20] power: supply: core: Refactor power_supply_set_input_current_limit_from

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Date:   Mon, 31 Jan 2022 15:39:35 +0100
From:   Hans de Goede <hdegoede@...hat.com>
To:     Andy Shevchenko <andriy.shevchenko@...el.com>
Cc:     "Rafael J . Wysocki" <rafael@...nel.org>,
        Mika Westerberg <mika.westerberg@...ux.intel.com>,
        Mark Gross <markgross@...nel.org>,
        Andy Shevchenko <andy@...nel.org>,
        Wolfram Sang <wsa@...nel.org>,
        Lee Jones <lee.jones@...aro.org>,
        Sebastian Reichel <sre@...nel.org>,
        MyungJoo Ham <myungjoo.ham@...sung.com>,
        Chanwoo Choi <cw00.choi@...sung.com>,
        Ard Biesheuvel <ardb@...nel.org>, Len Brown <lenb@...nel.org>,
        linux-acpi@...r.kernel.org, Yauhen Kharuzhy <jekhor@...il.com>,
        Tsuchiya Yuto <kitakar@...il.com>,
        Fabio Aiuto <fabioaiuto83@...il.com>,
        platform-driver-x86@...r.kernel.org, linux-pm@...r.kernel.org,
        linux-kernel@...r.kernel.org, linux-efi@...r.kernel.org
Subject: Re: [PATCH v4 01/20] power: supply: core: Refactor
 power_supply_set_input_current_limit_from_supplier()

Hi Andy,

Thank you for the reviews.

On 1/31/22 14:37, Andy Shevchenko wrote:
> On Sun, Jan 30, 2022 at 09:45:38PM +0100, Hans de Goede wrote:
>> Some (USB) charger ICs have variants with USB D+ and D- pins to do their
>> own builtin charger-type detection, like e.g. the bq24190 and bq25890 and
>> also variants which lack this functionality, e.g. the bq24192 and bq25892.
>>
>> In case the charger-type; and thus the input-current-limit detection is
>> done outside the charger IC then we need some way to communicate this to
>> the charger IC. In the past extcon was used for this, but if the external
>> detection does e.g. full USB PD negotiation then the extcon cable-types do
>> not convey enough information.
>>
>> For these setups it was decided to model the external charging "brick"
>> and the parameters negotiated with it as a power_supply class-device
>> itself; and power_supply_set_input_current_limit_from_supplier() was
>> introduced to allow drivers to get the input-current-limit this way.
>>
>> But in some cases psy drivers may want to know other properties, e.g. the
>> bq25892 can do "quick-charge" negotiation by pulsing its current draw,
>> but this should only be done if the usb_type psy-property of its supplier
>> is set to DCP (and device-properties indicate the board allows higher
>> voltages).
>>
>> Instead of adding extra helper functions for each property which
>> a psy-driver wants to query from its supplier, refactor
>> power_supply_set_input_current_limit_from_supplier() into a
>> more generic power_supply_get_property_from_supplier() function.
> 
> ...
> 
>> +	ret = power_supply_get_property_from_supplier(bdi->charger,
>> +						      POWER_SUPPLY_PROP_CURRENT_MAX,
>> +						      &val);
>> +	if (ret == 0)
> 
> Can it be as simple as
> 
> 	if (ret)
> 		return;
> 
> 	...
> 
> 
> ?
> 
> Or did I misunderstand the meaning of 0?

Yes that would be better and together with some of the other tweaks
you've suggested I believe that this warrants a version 5. So I'll
address a v5 addressing all your comment.

Regards,

Hans