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

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Date: Tue, 30 Jan 2024 03:02:09 +0100
From: Armin Wolf <W_Armin@....de>
To: Szilard Fabian <szfabian@...emarch.art>, linux-kernel@...r.kernel.org,
 platform-driver-x86@...r.kernel.org, jwoithe@...t42.net,
 hdegoede@...hat.com, ilpo.jarvinen@...ux.intel.com
Subject: Re: [RFC PATCH v2] platform/x86/fujitsu-laptop: Add battery charge
 control support

Am 29.01.24 um 19:00 schrieb Szilard Fabian:

> This patch adds battery charge control support on Fujitsu notebooks
> via the S006 method of the FUJ02E3 ACPI device. With this method it's
> possible to set charge_control_end_threshold between 50 and 100%.
>
> Tested on Lifebook E5411 and Lifebook U728. Sadly I can't test this
> patch on a dual battery one, but I didn't find any clue about
> independent battery charge control on dual battery Fujitsu notebooks
> either. And by that I mean checking the DSDT table of various Lifebook
> notebooks and reverse engineering FUJ02E3.dll.
>
> Signed-off-by: Szilard Fabian <szfabian@...emarch.art>
> ---
> v2:
> Forgot to sign-off the original commit. Fixed, sorry for the
> inconvenience.
> ---
>   drivers/platform/x86/fujitsu-laptop.c | 95 +++++++++++++++++++++++++++
>   1 file changed, 95 insertions(+)
>
> diff --git a/drivers/platform/x86/fujitsu-laptop.c b/drivers/platform/x86/fujitsu-laptop.c
> index 085e044e888e..bf3df74e4d63 100644
> --- a/drivers/platform/x86/fujitsu-laptop.c
> +++ b/drivers/platform/x86/fujitsu-laptop.c
> @@ -49,6 +49,8 @@
>   #include <linux/kfifo.h>
>   #include <linux/leds.h>
>   #include <linux/platform_device.h>
> +#include <linux/power_supply.h>
> +#include <acpi/battery.h>
>   #include <acpi/video.h>
>
>   #define FUJITSU_DRIVER_VERSION		"0.6.0"
> @@ -97,6 +99,10 @@
>   #define BACKLIGHT_OFF			(BIT(0) | BIT(1))
>   #define BACKLIGHT_ON			0
>
> +/* FUNC interface - battery control interface */
> +#define FUNC_S006_METHOD		0x1006
> +#define CHARGE_CONTROL_RW		0x21
> +
>   /* Scancodes read from the GIRB register */
>   #define KEY1_CODE			0x410
>   #define KEY2_CODE			0x411
> @@ -164,6 +170,91 @@ static int call_fext_func(struct acpi_device *device,
>   	return value;
>   }
>
> +/* Battery charge control code */
> +
> +static ssize_t charge_control_end_threshold_store(struct device *dev,
> +				struct device_attribute *attr,
> +				const char *buf, size_t count)
> +{
> +	int value, ret;
> +
> +	ret = kstrtouint(buf, 10, &value);
> +	if (ret)
> +		return ret;
> +
> +	if (value < 50 || value > 100)
> +		return -EINVAL;
> +
> +	int cc_end_value, s006_cc_return;
> +
> +	cc_end_value = value * 0x100 + 0x20;
> +	s006_cc_return = call_fext_func(fext, FUNC_S006_METHOD,
> +					CHARGE_CONTROL_RW, cc_end_value, 0x0);

Hi,

Error handling is missing for call_fext_func(), as it can return an negative error code.

> +
> +	/*
> +	 * The S006 0x21 method returns 0x00 in case the provided value
> +	 * is invalid.
> +	 */
> +	if (s006_cc_return == 0x00)
> +		return -EINVAL;
> +
> +	return count;
> +}
> +
> +static ssize_t charge_control_end_threshold_show(struct device *dev,
> +				struct device_attribute *attr,
> +				char *buf)
> +{
> +	int status;
> +	status = call_fext_func(fext, FUNC_S006_METHOD,
> +				CHARGE_CONTROL_RW, 0x21, 0x0);

Same as above.

> +
> +	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?

> +
> +	if (device_create_file(&battery->dev,
> +			       &dev_attr_charge_control_end_threshold))
> +		return -ENODEV;
> +
> +	return 0;

Better to just return the result of device_create_file() here.

Thanks,
Armin Wolf

> +}
> +
> +static int fujitsu_battery_remove(struct power_supply *battery,
> +				  struct acpi_battery_hook *hook)
> +{
> +	device_remove_file(&battery->dev,
> +			   &dev_attr_charge_control_end_threshold);
> +
> +	return 0;
> +}
> +
> +static struct acpi_battery_hook battery_hook = {
> +	.add_battery = fujitsu_battery_add,
> +	.remove_battery = fujitsu_battery_remove,
> +	.name = "Fujitsu Battery Extension",
> +};
> +
>   /* Hardware access for LCD brightness control */
>
>   static int set_lcd_level(struct acpi_device *device, int level)
> @@ -839,6 +930,8 @@ static int acpi_fujitsu_laptop_add(struct acpi_device *device)
>   	if (ret)
>   		goto err_free_fifo;
>
> +	battery_hook_register(&battery_hook);
> +
>   	return 0;
>
>   err_free_fifo:
> @@ -851,6 +944,8 @@ static void acpi_fujitsu_laptop_remove(struct acpi_device *device)
>   {
>   	struct fujitsu_laptop *priv = acpi_driver_data(device);
>
> +	battery_hook_unregister(&battery_hook);
> +
>   	fujitsu_laptop_platform_remove(device);
>
>   	kfifo_free(&priv->fifo);