[PATCH 0/3] power: supply: add battery driver for netronix ec

[PATCH 0/3] power: supply: add battery driver for netronix ec

[Josua Mayer]

Signed-off-by: Josua Mayer <josua.mayer@jm0.eu>
---
Josua Mayer (3):
      power: supply: add battery driver for netronix ec
      dt-bindings: mfd: netronix,ntxec: add reference to power-supply
      ARM: dts: imx: imx50-kobo-aura: add description for battery

 .../devicetree/bindings/mfd/netronix,ntxec.yaml    |   9 +-
 arch/arm/boot/dts/nxp/imx/imx50-kobo-aura.dts      |   9 ++
 drivers/mfd/ntxec.c                                |   1 +
 drivers/power/supply/Kconfig                       |   9 ++
 drivers/power/supply/Makefile                      |   1 +
 drivers/power/supply/ntxec-battery.c               | 101 +++++++++++++++++++++
 6 files changed, 127 insertions(+), 3 deletions(-)
---
base-commit: 8f0b4cce4481fb22653697cced8d0d04027cb1e8
change-id: 20251227-kobo-aura-battery-3e60bc159d16

Best regards,
-- 
Josua Mayer <josua.mayer@jm0.eu>

[PATCH 1/3] power: supply: add battery driver for netronix ec

[Josua Mayer]

Implement a simple battery driver for monitoring voltage with the
netronix embedded controller found in certain ebook readers.

Signed-off-by: Josua Mayer <josua.mayer@jm0.eu>
---
 drivers/mfd/ntxec.c                  |   1 +
 drivers/power/supply/Kconfig         |   9 ++++
 drivers/power/supply/Makefile        |   1 +
 drivers/power/supply/ntxec-battery.c | 101 +++++++++++++++++++++++++++++++++++
 4 files changed, 112 insertions(+)

diff --git a/drivers/mfd/ntxec.c b/drivers/mfd/ntxec.c
index 08c68de0f01bc..d5059b8862aa8 100644
--- a/drivers/mfd/ntxec.c
+++ b/drivers/mfd/ntxec.c
@@ -139,6 +139,7 @@ static const struct regmap_config regmap_config = {
 static const struct mfd_cell ntxec_subdev[] = {
 	{ .name = "ntxec-rtc" },
 	{ .name = "ntxec-pwm" },
+	{ .name = "ntxec-battery" },
 };
 
 static const struct mfd_cell ntxec_subdev_pwm[] = {
diff --git a/drivers/power/supply/Kconfig b/drivers/power/supply/Kconfig
index 92f9f7aae92f2..5674a23ba7bd6 100644
--- a/drivers/power/supply/Kconfig
+++ b/drivers/power/supply/Kconfig
@@ -1132,4 +1132,13 @@ config FUEL_GAUGE_MM8013
 	  the state of charge, temperature, cycle count, actual and design
 	  capacity, etc.
 
+config BATTERY_NTXEC
+	tristate "Battery driver for Netronix embedded controller"
+	depends on MFD_NTXEC
+	help
+	  Say yes here to enable netronix ec battery monitoring driver.
+	  It enables the monitoring battery voltage on certain e-book readers
+	  using an embedded controller by ODM Netronix. Battery design
+	  characteristics are read from Firmware Tables if available.
+
 endif # POWER_SUPPLY
diff --git a/drivers/power/supply/Makefile b/drivers/power/supply/Makefile
index 4b79d5abc49a7..db6fc815f9da2 100644
--- a/drivers/power/supply/Makefile
+++ b/drivers/power/supply/Makefile
@@ -128,3 +128,4 @@ obj-$(CONFIG_CHARGER_SURFACE)	+= surface_charger.o
 obj-$(CONFIG_BATTERY_UG3105)	+= ug3105_battery.o
 obj-$(CONFIG_CHARGER_QCOM_SMB2)	+= qcom_smbx.o
 obj-$(CONFIG_FUEL_GAUGE_MM8013)	+= mm8013.o
+obj-$(CONFIG_BATTERY_NTXEC)	+= ntxec-battery.o
diff --git a/drivers/power/supply/ntxec-battery.c b/drivers/power/supply/ntxec-battery.c
new file mode 100644
index 0000000000000..f49f0966d18dd
--- /dev/null
+++ b/drivers/power/supply/ntxec-battery.c
@@ -0,0 +1,101 @@
+// SPDX-License-Identifier: GPL-2.0-or-later
+/*
+ * The Netronix embedded controller is a microcontroller found in some
+ * e-book readers designed by the original design manufacturer Netronix, Inc.
+ * It contains RTC, battery monitoring, system power management, and PWM
+ * functionality.
+ *
+ * This driver implements battery monitoring.
+ *
+ * Copyright 2021 Josua Mayer <josua.mayer@jm0.eu>
+ */
+
+#include <linux/mfd/ntxec.h>
+#include <linux/module.h>
+#include <linux/platform_device.h>
+#include <linux/power_supply.h>
+#include <linux/property.h>
+#include <linux/regmap.h>
+
+static const enum power_supply_property ntxec_battery_properties[] = {
+	POWER_SUPPLY_PROP_VOLTAGE_NOW,
+};
+
+struct ntxec_battery {
+	struct ntxec *ec;
+};
+
+#define NTXEC_REG_READ_BATTERY	0x41
+
+static int ntxec_battery_get_property(struct power_supply *psy,
+				     enum power_supply_property psp,
+				     union power_supply_propval *val)
+{
+	struct ntxec_battery *priv = power_supply_get_drvdata(psy);
+	int ret;
+	unsigned int value;
+
+	switch (psp) {
+		case POWER_SUPPLY_PROP_VOLTAGE_NOW:
+			ret = regmap_read(priv->ec->regmap, NTXEC_REG_READ_BATTERY, &value);
+			if (ret < 0)
+				return ret;
+
+			/* ec value to microvolt conversion:
+			 * vendor kernel source suggests linear behaviour from 3V to 4.2V
+			 * with readings 767 to 1023; each increment represents 4687,5uV.
+			 * adjust 3V boundary slightly to report exactly 4.2V when full.
+			 */
+			val->intval = 2999872 + (value - 767) * 4688;
+			break;
+		default:
+			dev_err(&psy->dev, "%s: invalid property %u\n", __func__, psp);
+			return -EINVAL;
+	}
+
+	return 0;
+}
+
+static const struct power_supply_desc ntxec_battery_desc = {
+	.name = "ec-battery",
+	.type = POWER_SUPPLY_TYPE_BATTERY,
+	.properties = ntxec_battery_properties,
+	.get_property = ntxec_battery_get_property,
+	.num_properties = ARRAY_SIZE(ntxec_battery_properties),
+};
+
+static int ntxec_battery_probe(struct platform_device *pdev)
+{
+	struct device *dev = &pdev->dev;
+	struct ntxec *ec = dev_get_drvdata(dev->parent);
+	struct power_supply_config psy_cfg = {};
+	struct ntxec_battery *priv;
+	struct power_supply *psy;
+
+	priv = devm_kzalloc(dev, sizeof(*priv), GFP_KERNEL);
+	if (!priv)
+		return -ENOMEM;
+
+	priv->ec = ec;
+	psy_cfg.drv_data = priv;
+	psy_cfg.fwnode = dev_fwnode(dev->parent);
+	psy_cfg.no_wakeup_source = true;
+	psy = devm_power_supply_register(dev, &ntxec_battery_desc, &psy_cfg);
+	if (IS_ERR(psy))
+		return PTR_ERR(psy);
+
+	return 0;
+}
+
+static struct platform_driver ntxec_battery_driver = {
+	.driver = {
+		.name = "ntxec-battery",
+	},
+	.probe = ntxec_battery_probe,
+};
+module_platform_driver(ntxec_battery_driver);
+
+MODULE_AUTHOR("Josua Mayer <josua.mayer@jm0.eu>");
+MODULE_DESCRIPTION("Battery driver for Netronix EC");
+MODULE_LICENSE("GPL");
+MODULE_ALIAS("platform:ntxec-battery");

-- 
2.51.0

Re: [PATCH 1/3] power: supply: add battery driver for netronix ec

[Andreas Kemnade]

On Sat, 27 Dec 2025 17:28:13 +0100
Josua Mayer <josua.mayer@jm0.eu> wrote:

> Implement a simple battery driver for monitoring voltage with the
> netronix embedded controller found in certain ebook readers.
> 
> Signed-off-by: Josua Mayer <josua.mayer@jm0.eu>

This also produces a value somehow depending on battery voltage
on the Tolino vision.
[...]
> diff --git a/drivers/mfd/ntxec.c b/drivers/mfd/ntxec.c
> index 08c68de0f01bc..d5059b8862aa8 100644
> --- a/drivers/mfd/ntxec.c
> +++ b/drivers/mfd/ntxec.c
> @@ -139,6 +139,7 @@ static const struct regmap_config regmap_config = {
> static const struct mfd_cell ntxec_subdev[] = {
> 	{ .name = "ntxec-rtc" },
> 	{ .name = "ntxec-pwm" },
> +	{ .name = "ntxec-battery" },
> };
> 
> static const struct mfd_cell ntxec_subdev_pwm[] = {

I think that should be a separate patch for mfd.

[...]
> +	switch (psp) {
> +		case POWER_SUPPLY_PROP_VOLTAGE_NOW:
> +			ret = regmap_read(priv->ec->regmap, NTXEC_REG_READ_BATTERY, &value);
> +			if (ret < 0)
> +				return ret;
> +
> +			/* ec value to microvolt conversion:
> +			 * vendor kernel source suggests linear behaviour from 3V to 4.2V
> +			 * with readings 767 to 1023; each increment represents 4687,5uV.
> +			 * adjust 3V boundary slightly to report exactly 4.2V when full.
> +			 */
> +			val->intval = 2999872 + (value - 767) * 4688;
> +			break;
I find this code both in some kobo 2.6.35.3 code and on the tolino 3.0.35:

        const unsigned short battGasgauge[] = {
        //      3.0V, 3.1V, 3.2V, 3.3V, 3.4V, 3.5V, 3.6V, 3.7V, 3.8V, 3.9V, 4.0V, 4.1V, 4.2V,
//               743,  767,  791,  812,  835,  860,  885,  909,  935,  960,  985, 1010, 1023,
                 767,  791,  812,  833,  852,  877,  903,  928,  950,  979,  993, 1019, 1023,
        };

This does not look very linear... We have offsets
24
21
21
19
25
26
25
22
29
14
26
4

Do you have something looking more sane?
No idea what should produce such flaky offsets besides of
improper measurements. At least that should be commented.
And why do these tables exist at all?

Hmm, the more weird thing is that these voltages are translated linearly
inot capacity. So maybe they are just adjusted to have the capacity look
more sane. That would explain the 4 units step between 4.1V and 4.2V.
Having linear adc result -> voltage and nonlinear voltage-> capcity would
make more sense.

looking at such code snippet like this:
case POWER_SUPPLY_PROP_CAPACITY:
                if (POWER_SUPPLY_STATUS_NOT_CHARGING == g_ntx_bat_di->battery_status) {
                        val->intval = 100;
                        return 0;
                }
                value = ntx_up_battery_vol();
[...]
                                val->intval  = 100 - ((4100000 - value)/7000);


I am wondering whether we should just return capacity that way without
calculating voltage...

Regards,
Andreas

Re: [PATCH 1/3] power: supply: add battery driver for netronix ec

[Ing. Josua Mayer]

Am 27.12.25 um 22:38 schrieb Andreas Kemnade:
> On Sat, 27 Dec 2025 17:28:13 +0100
> Josua Mayer <josua.mayer@jm0.eu> wrote:
> 
>> Implement a simple battery driver for monitoring voltage with the
>> netronix embedded controller found in certain ebook readers.
>>
>> Signed-off-by: Josua Mayer <josua.mayer@jm0.eu>
> 
> This also produces a value somehow depending on battery voltage
> on the Tolino vision.
Good!

> [...]
>> diff --git a/drivers/mfd/ntxec.c b/drivers/mfd/ntxec.c
>> index 08c68de0f01bc..d5059b8862aa8 100644
>> --- a/drivers/mfd/ntxec.c
>> +++ b/drivers/mfd/ntxec.c
>> @@ -139,6 +139,7 @@ static const struct regmap_config regmap_config = {
>> static const struct mfd_cell ntxec_subdev[] = {
>> 	{ .name = "ntxec-rtc" },
>> 	{ .name = "ntxec-pwm" },
>> +	{ .name = "ntxec-battery" },
>> };
>>
>> static const struct mfd_cell ntxec_subdev_pwm[] = {
> 
> I think that should be a separate patch for mfd.
Okay

> [...]
>> +	switch (psp) {
>> +		case POWER_SUPPLY_PROP_VOLTAGE_NOW:
>> +			ret = regmap_read(priv->ec->regmap, NTXEC_REG_READ_BATTERY, &value);
>> +			if (ret < 0)
>> +				return ret;
>> +
>> +			/* ec value to microvolt conversion:
>> +			 * vendor kernel source suggests linear behaviour from 3V to 4.2V
>> +			 * with readings 767 to 1023; each increment represents 4687,5uV.
>> +			 * adjust 3V boundary slightly to report exactly 4.2V when full.
>> +			 */
>> +			val->intval = 2999872 + (value - 767) * 4688;
>> +			break;
> I find this code both in some kobo 2.6.35.3 code and on the tolino 3.0.35:
> 
>          const unsigned short battGasgauge[] = {
>          //      3.0V, 3.1V, 3.2V, 3.3V, 3.4V, 3.5V, 3.6V, 3.7V, 3.8V, 3.9V, 4.0V, 4.1V, 4.2V,
> //               743,  767,  791,  812,  835,  860,  885,  909,  935,  960,  985, 1010, 1023,
>                   767,  791,  812,  833,  852,  877,  903,  928,  950,  979,  993, 1019, 1023,
>          };
> 
> This does not look very linear... We have offsets
> 24
> 21
> 21
> 19
> 25
> 26
> 25
> 22
> 29
> 14
> 26
> 4
> 
> Do you have something looking more sane?
No, I based on the same but simplified it.
> No idea what should produce such flaky offsets besides of
> improper measurements. At least that should be commented.
> And why do these tables exist at all?
> 
> Hmm, the more weird thing is that these voltages are translated linearly
> inot capacity.
Indeed - this is why I decided on a linear relationship ...
matching minimal and maixmal voltage as close as possible.

> So maybe they are just adjusted to have the capacity look
> more sane. That would explain the 4 units step between 4.1V and 4.2V.
4.1 is the full voltage of the lion battery if charger was disconnected.
However 4.2 I think is the final voltage reached while charging.

> Having linear adc result -> voltage and nonlinear voltage-> capcity would
> make more sense.
Indeed.
But if it was intended as percentage, then why would he register not 
just read from 0-100 :(
So I still guess it is some adc result.

> 
> looking at such code snippet like this:
> case POWER_SUPPLY_PROP_CAPACITY:
>                  if (POWER_SUPPLY_STATUS_NOT_CHARGING == g_ntx_bat_di->battery_status) {
>                          val->intval = 100;
>                          return 0;
>                  }
>                  value = ntx_up_battery_vol();
> [...]
>                                  val->intval  = 100 - ((4100000 - value)/7000);
> 
> 
> I am wondering whether we should just return capacity that way without
> calculating voltage...
I suppose it depends on whether it is more likely that the ec provides 
voltage, or a charge estimation.

br
Josua

Re: [PATCH 1/3] power: supply: add battery driver for netronix ec

[J. Neuschäfer]

Hello!

Nice to see someone work on the Netronix EC :-)

On Sat, Dec 27, 2025 at 05:28:13PM +0100, Josua Mayer wrote:
> Implement a simple battery driver for monitoring voltage with the
> netronix embedded controller found in certain ebook readers.
> 
> Signed-off-by: Josua Mayer <josua.mayer@jm0.eu>
> ---
>  drivers/mfd/ntxec.c                  |   1 +
>  drivers/power/supply/Kconfig         |   9 ++++
>  drivers/power/supply/Makefile        |   1 +
>  drivers/power/supply/ntxec-battery.c | 101 +++++++++++++++++++++++++++++++++++
>  4 files changed, 112 insertions(+)
> 
> diff --git a/drivers/mfd/ntxec.c b/drivers/mfd/ntxec.c
> index 08c68de0f01bc..d5059b8862aa8 100644
> --- a/drivers/mfd/ntxec.c
> +++ b/drivers/mfd/ntxec.c
> @@ -139,6 +139,7 @@ static const struct regmap_config regmap_config = {
>  static const struct mfd_cell ntxec_subdev[] = {
>  	{ .name = "ntxec-rtc" },
>  	{ .name = "ntxec-pwm" },
> +	{ .name = "ntxec-battery" },
>  };
>  
>  static const struct mfd_cell ntxec_subdev_pwm[] = {
> diff --git a/drivers/power/supply/Kconfig b/drivers/power/supply/Kconfig
> index 92f9f7aae92f2..5674a23ba7bd6 100644
> --- a/drivers/power/supply/Kconfig
> +++ b/drivers/power/supply/Kconfig
> @@ -1132,4 +1132,13 @@ config FUEL_GAUGE_MM8013
>  	  the state of charge, temperature, cycle count, actual and design
>  	  capacity, etc.
>  
> +config BATTERY_NTXEC
> +	tristate "Battery driver for Netronix embedded controller"
> +	depends on MFD_NTXEC
> +	help
> +	  Say yes here to enable netronix ec battery monitoring driver.
> +	  It enables the monitoring battery voltage on certain e-book readers
> +	  using an embedded controller by ODM Netronix. Battery design
> +	  characteristics are read from Firmware Tables if available.

What do you mean by Firmware Tables, and where does this happen?

(I guess it means devicetree/fwnode, but "git grep -i 'firmware tables'"
doesn't show many uses of that term)

> +
>  endif # POWER_SUPPLY
> diff --git a/drivers/power/supply/Makefile b/drivers/power/supply/Makefile
> index 4b79d5abc49a7..db6fc815f9da2 100644
> --- a/drivers/power/supply/Makefile
> +++ b/drivers/power/supply/Makefile
> @@ -128,3 +128,4 @@ obj-$(CONFIG_CHARGER_SURFACE)	+= surface_charger.o
>  obj-$(CONFIG_BATTERY_UG3105)	+= ug3105_battery.o
>  obj-$(CONFIG_CHARGER_QCOM_SMB2)	+= qcom_smbx.o
>  obj-$(CONFIG_FUEL_GAUGE_MM8013)	+= mm8013.o
> +obj-$(CONFIG_BATTERY_NTXEC)	+= ntxec-battery.o
> diff --git a/drivers/power/supply/ntxec-battery.c b/drivers/power/supply/ntxec-battery.c
> new file mode 100644
> index 0000000000000..f49f0966d18dd
> --- /dev/null
> +++ b/drivers/power/supply/ntxec-battery.c
> @@ -0,0 +1,101 @@
> +// SPDX-License-Identifier: GPL-2.0-or-later
> +/*
> + * The Netronix embedded controller is a microcontroller found in some
> + * e-book readers designed by the original design manufacturer Netronix, Inc.
> + * It contains RTC, battery monitoring, system power management, and PWM
> + * functionality.
> + *
> + * This driver implements battery monitoring.
> + *
> + * Copyright 2021 Josua Mayer <josua.mayer@jm0.eu>
> + */
> +
> +#include <linux/mfd/ntxec.h>
> +#include <linux/module.h>
> +#include <linux/platform_device.h>
> +#include <linux/power_supply.h>
> +#include <linux/property.h>
> +#include <linux/regmap.h>
> +
> +static const enum power_supply_property ntxec_battery_properties[] = {
> +	POWER_SUPPLY_PROP_VOLTAGE_NOW,
> +};
> +
> +struct ntxec_battery {
> +	struct ntxec *ec;
> +};
> +
> +#define NTXEC_REG_READ_BATTERY	0x41
> +
> +static int ntxec_battery_get_property(struct power_supply *psy,
> +				     enum power_supply_property psp,
> +				     union power_supply_propval *val)
> +{
> +	struct ntxec_battery *priv = power_supply_get_drvdata(psy);
> +	int ret;
> +	unsigned int value;
> +
> +	switch (psp) {
> +		case POWER_SUPPLY_PROP_VOLTAGE_NOW:
> +			ret = regmap_read(priv->ec->regmap, NTXEC_REG_READ_BATTERY, &value);
> +			if (ret < 0)
> +				return ret;
> +
> +			/* ec value to microvolt conversion:
> +			 * vendor kernel source suggests linear behaviour from 3V to 4.2V
> +			 * with readings 767 to 1023; each increment represents 4687,5uV.
> +			 * adjust 3V boundary slightly to report exactly 4.2V when full.
> +			 */
> +			val->intval = 2999872 + (value - 767) * 4688;
> +			break;
> +		default:
> +			dev_err(&psy->dev, "%s: invalid property %u\n", __func__, psp);
> +			return -EINVAL;
> +	}
> +
> +	return 0;
> +}
> +
> +static const struct power_supply_desc ntxec_battery_desc = {
> +	.name = "ec-battery",
> +	.type = POWER_SUPPLY_TYPE_BATTERY,
> +	.properties = ntxec_battery_properties,
> +	.get_property = ntxec_battery_get_property,
> +	.num_properties = ARRAY_SIZE(ntxec_battery_properties),
> +};
> +
> +static int ntxec_battery_probe(struct platform_device *pdev)
> +{
> +	struct device *dev = &pdev->dev;
> +	struct ntxec *ec = dev_get_drvdata(dev->parent);
> +	struct power_supply_config psy_cfg = {};
> +	struct ntxec_battery *priv;
> +	struct power_supply *psy;
> +
> +	priv = devm_kzalloc(dev, sizeof(*priv), GFP_KERNEL);
> +	if (!priv)
> +		return -ENOMEM;
> +
> +	priv->ec = ec;
> +	psy_cfg.drv_data = priv;
> +	psy_cfg.fwnode = dev_fwnode(dev->parent);
> +	psy_cfg.no_wakeup_source = true;
> +	psy = devm_power_supply_register(dev, &ntxec_battery_desc, &psy_cfg);
> +	if (IS_ERR(psy))
> +		return PTR_ERR(psy);
> +
> +	return 0;
> +}
> +
> +static struct platform_driver ntxec_battery_driver = {
> +	.driver = {
> +		.name = "ntxec-battery",
> +	},
> +	.probe = ntxec_battery_probe,
> +};
> +module_platform_driver(ntxec_battery_driver);
> +
> +MODULE_AUTHOR("Josua Mayer <josua.mayer@jm0.eu>");
> +MODULE_DESCRIPTION("Battery driver for Netronix EC");
> +MODULE_LICENSE("GPL");
> +MODULE_ALIAS("platform:ntxec-battery");

Thanks,
J. Neuschäfer

Re: [PATCH 1/3] power: supply: add battery driver for netronix ec

[Ing. Josua Mayer]

Am 28.12.25 um 18:56 schrieb J. Neuschäfer:
> Hello!
> 
> Nice to see someone work on the Netronix EC :-)
> 
> On Sat, Dec 27, 2025 at 05:28:13PM +0100, Josua Mayer wrote:
>> Implement a simple battery driver for monitoring voltage with the
>> netronix embedded controller found in certain ebook readers.
>>
>> Signed-off-by: Josua Mayer <josua.mayer@jm0.eu>
>> ---
>>   drivers/mfd/ntxec.c                  |   1 +
>>   drivers/power/supply/Kconfig         |   9 ++++
>>   drivers/power/supply/Makefile        |   1 +
>>   drivers/power/supply/ntxec-battery.c | 101 +++++++++++++++++++++++++++++++++++
>>   4 files changed, 112 insertions(+)
>>
>> diff --git a/drivers/mfd/ntxec.c b/drivers/mfd/ntxec.c
>> index 08c68de0f01bc..d5059b8862aa8 100644
>> --- a/drivers/mfd/ntxec.c
>> +++ b/drivers/mfd/ntxec.c
>> @@ -139,6 +139,7 @@ static const struct regmap_config regmap_config = {
>>   static const struct mfd_cell ntxec_subdev[] = {
>>   	{ .name = "ntxec-rtc" },
>>   	{ .name = "ntxec-pwm" },
>> +	{ .name = "ntxec-battery" },
>>   };
>>   
>>   static const struct mfd_cell ntxec_subdev_pwm[] = {
>> diff --git a/drivers/power/supply/Kconfig b/drivers/power/supply/Kconfig
>> index 92f9f7aae92f2..5674a23ba7bd6 100644
>> --- a/drivers/power/supply/Kconfig
>> +++ b/drivers/power/supply/Kconfig
>> @@ -1132,4 +1132,13 @@ config FUEL_GAUGE_MM8013
>>   	  the state of charge, temperature, cycle count, actual and design
>>   	  capacity, etc.
>>   
>> +config BATTERY_NTXEC
>> +	tristate "Battery driver for Netronix embedded controller"
>> +	depends on MFD_NTXEC
>> +	help
>> +	  Say yes here to enable netronix ec battery monitoring driver.
>> +	  It enables the monitoring battery voltage on certain e-book readers
>> +	  using an embedded controller by ODM Netronix. Battery design
>> +	  characteristics are read from Firmware Tables if available.
> 
> What do you mean by Firmware Tables, and where does this happen?
Effectively I mean device-tree.

This happens in power-supply core automatically for type battery:

static struct power_supply *__must_check
__power_supply_register(struct device *parent,
				   const struct power_supply_desc *desc,
				   const struct power_supply_config *cfg)
{
	...
	/*
	 * Expose constant battery info, if it is available. While there are
	 * some chargers accessing constant battery data, we only want to
	 * expose battery data to userspace for battery devices.
	 */
	if (desc->type == POWER_SUPPLY_TYPE_BATTERY) {
		rc = power_supply_get_battery_info(psy, &psy->battery_info);
		if (rc && rc != -ENODEV && rc != -ENOENT)
			goto check_supplies_failed;
	}
	...
}

This code particular is the reason I marked it optional in DT binding.

> 
> (I guess it means devicetree/fwnode, but "git grep -i 'firmware tables'"
Yes, given that power_supply_get_battery_info uses fwnode_* functions.

> doesn't show many uses of that term)
I was struggling with the phrasing - can change to something better.

> 
>> +
>>   endif # POWER_SUPPLY
>> diff --git a/drivers/power/supply/Makefile b/drivers/power/supply/Makefile
>> index 4b79d5abc49a7..db6fc815f9da2 100644
>> --- a/drivers/power/supply/Makefile
>> +++ b/drivers/power/supply/Makefile
>> @@ -128,3 +128,4 @@ obj-$(CONFIG_CHARGER_SURFACE)	+= surface_charger.o
>>   obj-$(CONFIG_BATTERY_UG3105)	+= ug3105_battery.o
>>   obj-$(CONFIG_CHARGER_QCOM_SMB2)	+= qcom_smbx.o
>>   obj-$(CONFIG_FUEL_GAUGE_MM8013)	+= mm8013.o
>> +obj-$(CONFIG_BATTERY_NTXEC)	+= ntxec-battery.o
>> diff --git a/drivers/power/supply/ntxec-battery.c b/drivers/power/supply/ntxec-battery.c
>> new file mode 100644
>> index 0000000000000..f49f0966d18dd
>> --- /dev/null
>> +++ b/drivers/power/supply/ntxec-battery.c
>> @@ -0,0 +1,101 @@
>> +// SPDX-License-Identifier: GPL-2.0-or-later
>> +/*
>> + * The Netronix embedded controller is a microcontroller found in some
>> + * e-book readers designed by the original design manufacturer Netronix, Inc.
>> + * It contains RTC, battery monitoring, system power management, and PWM
>> + * functionality.
>> + *
>> + * This driver implements battery monitoring.
>> + *
>> + * Copyright 2021 Josua Mayer <josua.mayer@jm0.eu>
>> + */
>> +
>> +#include <linux/mfd/ntxec.h>
>> +#include <linux/module.h>
>> +#include <linux/platform_device.h>
>> +#include <linux/power_supply.h>
>> +#include <linux/property.h>
>> +#include <linux/regmap.h>
>> +
>> +static const enum power_supply_property ntxec_battery_properties[] = {
>> +	POWER_SUPPLY_PROP_VOLTAGE_NOW,
>> +};
>> +
>> +struct ntxec_battery {
>> +	struct ntxec *ec;
>> +};
>> +
>> +#define NTXEC_REG_READ_BATTERY	0x41
>> +
>> +static int ntxec_battery_get_property(struct power_supply *psy,
>> +				     enum power_supply_property psp,
>> +				     union power_supply_propval *val)
>> +{
>> +	struct ntxec_battery *priv = power_supply_get_drvdata(psy);
>> +	int ret;
>> +	unsigned int value;
>> +
>> +	switch (psp) {
>> +		case POWER_SUPPLY_PROP_VOLTAGE_NOW:
>> +			ret = regmap_read(priv->ec->regmap, NTXEC_REG_READ_BATTERY, &value);
>> +			if (ret < 0)
>> +				return ret;
>> +
>> +			/* ec value to microvolt conversion:
>> +			 * vendor kernel source suggests linear behaviour from 3V to 4.2V
>> +			 * with readings 767 to 1023; each increment represents 4687,5uV.
>> +			 * adjust 3V boundary slightly to report exactly 4.2V when full.
>> +			 */
>> +			val->intval = 2999872 + (value - 767) * 4688;
>> +			break;
>> +		default:
>> +			dev_err(&psy->dev, "%s: invalid property %u\n", __func__, psp);
>> +			return -EINVAL;
>> +	}
>> +
>> +	return 0;
>> +}
>> +
>> +static const struct power_supply_desc ntxec_battery_desc = {
>> +	.name = "ec-battery",
>> +	.type = POWER_SUPPLY_TYPE_BATTERY,
>> +	.properties = ntxec_battery_properties,
>> +	.get_property = ntxec_battery_get_property,
>> +	.num_properties = ARRAY_SIZE(ntxec_battery_properties),
>> +};
>> +
>> +static int ntxec_battery_probe(struct platform_device *pdev)
>> +{
>> +	struct device *dev = &pdev->dev;
>> +	struct ntxec *ec = dev_get_drvdata(dev->parent);
>> +	struct power_supply_config psy_cfg = {};
>> +	struct ntxec_battery *priv;
>> +	struct power_supply *psy;
>> +
>> +	priv = devm_kzalloc(dev, sizeof(*priv), GFP_KERNEL);
>> +	if (!priv)
>> +		return -ENOMEM;
>> +
>> +	priv->ec = ec;
>> +	psy_cfg.drv_data = priv;
>> +	psy_cfg.fwnode = dev_fwnode(dev->parent);
>> +	psy_cfg.no_wakeup_source = true;
>> +	psy = devm_power_supply_register(dev, &ntxec_battery_desc, &psy_cfg);
>> +	if (IS_ERR(psy))
>> +		return PTR_ERR(psy);
>> +
>> +	return 0;
>> +}
>> +
>> +static struct platform_driver ntxec_battery_driver = {
>> +	.driver = {
>> +		.name = "ntxec-battery",
>> +	},
>> +	.probe = ntxec_battery_probe,
>> +};
>> +module_platform_driver(ntxec_battery_driver);
>> +
>> +MODULE_AUTHOR("Josua Mayer <josua.mayer@jm0.eu>");
>> +MODULE_DESCRIPTION("Battery driver for Netronix EC");
>> +MODULE_LICENSE("GPL");
>> +MODULE_ALIAS("platform:ntxec-battery");
> 
> Thanks,
> J. Neuschäfer

[PATCH 2/3] dt-bindings: mfd: netronix,ntxec: add reference to power-supply

[Josua Mayer]

The Netronix Embedded Controller supports monitoring of battery voltage.

Voltage monitoring functionality is self-contained and requires no
supply- or battery-specific runtime configuration.

Battery design characteristics (e.g. voltage-min-design-microvolt) are
useful for users to understand the charge level and are commonly
provided by a separate battery node linked with monitored-battery
property.

Add reference to power-supply.yaml so that power-supplies and
monitored-battery properties become available.

Further drop reg property description and replace it with maxItems 1 as
is common for i2c devices with single bus address.

Finally replace additionalProperties with unevaluatedProperties to
allow properties from referenced schemas.

Signed-off-by: Josua Mayer <josua@solid-run.com>
---
 Documentation/devicetree/bindings/mfd/netronix,ntxec.yaml | 9 ++++++---
 1 file changed, 6 insertions(+), 3 deletions(-)

diff --git a/Documentation/devicetree/bindings/mfd/netronix,ntxec.yaml b/Documentation/devicetree/bindings/mfd/netronix,ntxec.yaml
index 37fbb953ea12e..6599dcf0eceb0 100644
--- a/Documentation/devicetree/bindings/mfd/netronix,ntxec.yaml
+++ b/Documentation/devicetree/bindings/mfd/netronix,ntxec.yaml
@@ -13,13 +13,15 @@ description: |
   This EC is found in e-book readers of multiple brands (e.g. Kobo, Tolino), and
   is typically implemented as a TI MSP430 microcontroller.
 
+allOf:
+  - $ref: /schemas/power/supply/power-supply.yaml
+
 properties:
   compatible:
     const: netronix,ntxec
 
   reg:
-    items:
-      - description: The I2C address of the EC
+    maxItems: 1
 
   system-power-controller:
     type: boolean
@@ -42,7 +44,7 @@ required:
   - compatible
   - reg
 
-additionalProperties: false
+unevaluatedProperties: false
 
 examples:
   - |
@@ -61,5 +63,6 @@ examples:
                 interrupt-parent = <&gpio4>;
                 interrupts = <11 IRQ_TYPE_EDGE_FALLING>;
                 #pwm-cells = <2>;
+                monitored-battery = <&battery>;
         };
     };

-- 
2.51.0

Re: [PATCH 2/3] dt-bindings: mfd: netronix,ntxec: add reference to power-supply

[Krzysztof Kozlowski]

On Sat, Dec 27, 2025 at 05:28:14PM +0100, Josua Mayer wrote:
> The Netronix Embedded Controller supports monitoring of battery voltage.
> 
> Voltage monitoring functionality is self-contained and requires no
> supply- or battery-specific runtime configuration.
> 
> Battery design characteristics (e.g. voltage-min-design-microvolt) are
> useful for users to understand the charge level and are commonly
> provided by a separate battery node linked with monitored-battery
> property.
> 
> Add reference to power-supply.yaml so that power-supplies and
> monitored-battery properties become available.
> 
> Further drop reg property description and replace it with maxItems 1 as
> is common for i2c devices with single bus address.
> 
> Finally replace additionalProperties with unevaluatedProperties to
> allow properties from referenced schemas.
> 
> Signed-off-by: Josua Mayer <josua@solid-run.com>

This does not match From address. Please use consistent identities for
both.

Best regards,
Krzysztof

[PATCH 3/3] ARM: dts: imx: imx50-kobo-aura: add description for battery

[Josua Mayer]

Kobo Aura has a rechargable battery that is monitored by the embedded
controller.

Battery markings: PR-285083 3.7V Typ. 1500mAh; 575327416288 5.55Wh.

Add description for this battery and link it for monitoring by the
embedded controller.

Signed-off-by: Josua Mayer <josua.mayer@jm0.eu>
---
 arch/arm/boot/dts/nxp/imx/imx50-kobo-aura.dts | 9 +++++++++
 1 file changed, 9 insertions(+)

diff --git a/arch/arm/boot/dts/nxp/imx/imx50-kobo-aura.dts b/arch/arm/boot/dts/nxp/imx/imx50-kobo-aura.dts
index b1a6a9c58ac33..dc8d9fd45cd23 100644
--- a/arch/arm/boot/dts/nxp/imx/imx50-kobo-aura.dts
+++ b/arch/arm/boot/dts/nxp/imx/imx50-kobo-aura.dts
@@ -16,6 +16,14 @@ chosen {
 		stdout-path = "serial1:115200n8";
 	};
 
+	battery: battery {
+		compatible = "simple-battery";
+		voltage-min-design-microvolt = <3400000>;
+		voltage-max-design-microvolt = <4100000>;
+		energy-full-design-microwatt-hours = <5550000>;
+		charge-full-design-microamp-hours = <1500000>;
+	};
+
 	memory@70000000 {
 		device_type = "memory";
 		reg = <0x70000000 0x10000000>;
@@ -151,6 +159,7 @@ embedded-controller@43 {
 		system-power-controller;
 		interrupts-extended = <&gpio4 11 IRQ_TYPE_EDGE_FALLING>;
 		#pwm-cells = <2>;
+		monitored-battery = <&battery>;
 	};
 };
 

-- 
2.51.0

Re: [PATCH 3/3] ARM: dts: imx: imx50-kobo-aura: add description for battery

[J. Neuschäfer]

On Sat, Dec 27, 2025 at 05:28:15PM +0100, Josua Mayer wrote:
> Kobo Aura has a rechargable battery that is monitored by the embedded
> controller.
> 
> Battery markings: PR-285083 3.7V Typ. 1500mAh; 575327416288 5.55Wh.
> 
> Add description for this battery and link it for monitoring by the
> embedded controller.
> 
> Signed-off-by: Josua Mayer <josua.mayer@jm0.eu>
> ---

Reviewed-by: J. Neuschäfer <j.neuschaefer@gmx.net>

Thanks!

>  arch/arm/boot/dts/nxp/imx/imx50-kobo-aura.dts | 9 +++++++++
>  1 file changed, 9 insertions(+)
> 
> diff --git a/arch/arm/boot/dts/nxp/imx/imx50-kobo-aura.dts b/arch/arm/boot/dts/nxp/imx/imx50-kobo-aura.dts
> index b1a6a9c58ac33..dc8d9fd45cd23 100644
> --- a/arch/arm/boot/dts/nxp/imx/imx50-kobo-aura.dts
> +++ b/arch/arm/boot/dts/nxp/imx/imx50-kobo-aura.dts
> @@ -16,6 +16,14 @@ chosen {
>  		stdout-path = "serial1:115200n8";
>  	};
>  
> +	battery: battery {
> +		compatible = "simple-battery";
> +		voltage-min-design-microvolt = <3400000>;
> +		voltage-max-design-microvolt = <4100000>;
> +		energy-full-design-microwatt-hours = <5550000>;
> +		charge-full-design-microamp-hours = <1500000>;
> +	};
> +
>  	memory@70000000 {
>  		device_type = "memory";
>  		reg = <0x70000000 0x10000000>;
> @@ -151,6 +159,7 @@ embedded-controller@43 {
>  		system-power-controller;
>  		interrupts-extended = <&gpio4 11 IRQ_TYPE_EDGE_FALLING>;
>  		#pwm-cells = <2>;
> +		monitored-battery = <&battery>;
>  	};
>  };
>  
> 
> -- 
> 2.51.0
>