linux-kernel - Re: [RFC PATCH v2] platform/x86/fujitsu-laptop: Add battery charge control support

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Date: Mon, 5 Feb 2024 18:07:46 +0100
From: Armin Wolf <W_Armin@....de>
To: Szilard Fabian <szfabian@...emarch.art>
Cc: hdegoede@...hat.com, ilpo.jarvinen@...ux.intel.com, jwoithe@...t42.net,
 linux-kernel@...r.kernel.org, platform-driver-x86@...r.kernel.org
Subject: Re: [RFC PATCH v2] platform/x86/fujitsu-laptop: Add battery charge
 control support

Am 03.02.24 um 01:17 schrieb Szilard Fabian:

> Hello,
>
> On Tue, Jan 30, 2024 at 03:02:09AM +0100, Armin Wolf wrote:
>> Am 29.01.24 um 19:00 schrieb Szilard Fabian:
>>> +
>>> +	return sprintf(buf, "%d\n", status);
>>> +}
>>> +
>>> +static DEVICE_ATTR_RW(charge_control_end_threshold);
>>> +
>>> +/* ACPI battery hook */
>>> +
>>> +static int fujitsu_battery_add(struct power_supply *battery,
>>> +			       struct acpi_battery_hook *hook)
>>> +{
>>> +	/* Check if there is an existing FUJ02E3 ACPI device. */
>>> +	if (fext == NULL)
>>> +		return -ENODEV;
>> Can you put the struct acpi_battery_hook into the struct fujitsu_laptop
>> and then use container_of() to retrieve the ACPI device from there?
>> The dell-wmi-ddv driver does something similar.
>>
>> This would guarantee that the battery hook always accesses the correct ACPI device
>> and you could drop this check.
>>
>>> +
>>> +	/*
>>> +	 * Check if the S006 0x21 method exists by trying to get the current
>>> +	 * battery charge limit.
>>> +	 */
>>> +	int s006_cc_return;
>>> +	s006_cc_return = call_fext_func(fext, FUNC_S006_METHOD,
>>> +					CHARGE_CONTROL_RW, 0x21, 0x0);
>>> +	if (s006_cc_return == UNSUPPORTED_CMD)
>>> +		return -ENODEV;
>> Maybe this check should be done once during probe?
> What about the following scenario?
> - Put a bool into the struct fujitsu_laptop to store information about the
>    machine's charge control ability.
> - The S006 0x21 method check with `battery_hook_register` gets moved into
>    an 'init function'. In that 'init function' the bool gets set accordingly.
> - `battery_hook_unregister` gets moved into an 'exit function', where the
>    bool gets read and when it's false nothing happens.
> - `fext` check gets removed from `fujitsu_battery_add` because it's
>    redundant (more about that later).
> - The 'init function' gets called in `acpi_fujitsu_laptop_add` and the 'exit
>    function' gets called in `acpi_fujitsu_laptop_remove`.
>
> With that scenario the code could be a little bit clearer in my opinion.
> And it is possible to drop the `fext` check because if the FUJ02E3 ACPI
> device exists `fext` gets set in the `acpi_fujitsu_laptop_add` function with
> an error check.
> (And the `fujitsu_battery_add` `fext` check was already redundant because
> `battery_hook_register` got called in `acpi_fujitsu_laptop_add`. `fext`
> gets set in the same function, and there is an error check already.)
>
> Thanks,
> Szilard
>
This would work too.

Armin Wolf