[PATCH v6] bq27xxx: support interchangeable OnePlus 6/6T fuel gauges

[PATCH v6] bq27xxx: support interchangeable OnePlus 6/6T fuel gauges

[Rinat Muhamedgaliev via B4 Relay]

OnePlus 6 and 6T replacement battery packs can contain either a bq27411 or a
bq27541 fuel gauge. The latter requires a different register map and produces
invalid battery readings when interpreted as a bq27411.

The I2C driver reads DeviceType while probing either of those compatible
devices and selects the matching profile.

The bq27541 path was tested on a OnePlus 6T with DeviceType 0x0541. It
reported 4.338 V, 100% capacity, 27.8 C, and Full/Good battery status.
Testing on an OnePlus 6 or 6T whose fuel gauge reports DeviceType 0x0421
(bq27411) would be appreciated.

Changes in v6:
- Compare the detected model with the compatible-selected model.
- Support both BQ27411-to-BQ27541 and BQ27541-to-BQ27411 detection.
- Document the pair of models checked at probe time.
- Link to v5: https://patch.msgid.link/20261018-master-v5-0-0be16441cdd1@gmail.com

Changes in v5:
- Report detected and expected DeviceType values instead of hard-coding chip names.
- Describe an unknown DeviceType as unrecognized.
- Link to v4: https://patch.msgid.link/20260928-master-v4-1-052c73ec1767@gmail.com

Changes in v4:
- Drop the generic compatible and binding update.
- Keep the established OnePlus DTS unchanged.
- Detect bq27541 from DeviceType in the bq27411 probe path.
- Send as a new thread.

---
Rinat Muhamedgaliev (1):
      power: supply: bq27xxx: detect bq27541 behind bq27411 compatible

 drivers/power/supply/bq27xxx_battery_i2c.c | 57 ++++++++++++++++++++++++++++++
 1 file changed, 57 insertions(+)
---
base-commit: 830b3c68c1fb1e9176028d02ef86f3cf76aa2476
change-id: 20260927-master-bd0afd9696ef

Best regards,
--  
Rinat Muhamedgaliev <rinat.muhamedgaliev@gmail.com>

[PATCH v6] power: supply: bq27xxx: detect bq27541 behind bq27411 compatible

[Rinat Muhamedgaliev via B4 Relay]

From: Rinat Muhamedgaliev <rinat.muhamedgaliev@gmail.com>

OnePlus 6 and 6T replacement battery packs may contain either a bq27411
or a bq27541 fuel gauge at I2C address 0x55. The device tree currently
identifies the gauge as bq27411, but a bq27541 uses a different register
map and then reports invalid battery values.

Read the DeviceType control subcommand when probing a bq27411. Keep the
existing profile for DeviceType 0x0421, but select the bq27541 profile
for DeviceType 0x0541. This retains the established DT ABI and supports
replacement packs without introducing a generic compatible.

Tested on OnePlus 6T (fajita) with DeviceType 0x0541: voltage, state of
charge, and temperature were reported correctly. Testing on hardware with
DeviceType 0x0421 would be appreciated.

Signed-off-by: Rinat Muhamedgaliev <rinat.muhamedgaliev@gmail.com>
---
 drivers/power/supply/bq27xxx_battery_i2c.c | 57 ++++++++++++++++++++++++++++++
 1 file changed, 57 insertions(+)

diff --git a/drivers/power/supply/bq27xxx_battery_i2c.c b/drivers/power/supply/bq27xxx_battery_i2c.c
index 94b00bb89c17..0b957888ad2b 100644
--- a/drivers/power/supply/bq27xxx_battery_i2c.c
+++ b/drivers/power/supply/bq27xxx_battery_i2c.c
@@ -16,6 +16,11 @@
 static DEFINE_IDR(battery_id);
 static DEFINE_MUTEX(battery_mutex);
 
+#define BQ27XXX_REG_CTRL		0x00
+#define BQ27XXX_DEVICE_TYPE		0x0001
+#define BQ27411_DEVICE_TYPE		0x0421
+#define BQ27541_DEVICE_TYPE		0x0541
+
 static irqreturn_t bq27xxx_battery_irq_handler_thread(int irq, void *data)
 {
 	struct bq27xxx_device_info *di = data;
@@ -136,6 +141,46 @@ static int bq27xxx_battery_i2c_bulk_write(struct bq27xxx_device_info *di,
 	return 0;
 }
 
+static int bq27xxx_battery_i2c_check_device_type(struct bq27xxx_device_info *di)
+{
+	enum bq27xxx_chip detected_chip;
+	int expected_type;
+	int ret;
+
+	ret = di->bus.write(di, BQ27XXX_REG_CTRL, BQ27XXX_DEVICE_TYPE,
+			    false);
+	if (ret < 0)
+		return ret;
+
+	ret = di->bus.read(di, BQ27XXX_REG_CTRL, false);
+	if (ret < 0)
+		return ret;
+
+	switch (ret) {
+	case BQ27411_DEVICE_TYPE:
+		detected_chip = BQ27411;
+		break;
+	case BQ27541_DEVICE_TYPE:
+		detected_chip = BQ27541;
+		break;
+	default:
+		dev_err(di->dev, "unrecognized DeviceType 0x%04x\n", ret);
+		return -ENODEV;
+	}
+
+	if (detected_chip == di->chip)
+		return 0;
+
+	expected_type = di->chip == BQ27411 ? BQ27411_DEVICE_TYPE :
+		BQ27541_DEVICE_TYPE;
+	dev_warn(di->dev,
+		 "detected DeviceType 0x%04x instead of expected 0x%04x\n",
+		 ret, expected_type);
+	di->chip = detected_chip;
+
+	return 0;
+}
+
 static int bq27xxx_battery_i2c_probe(struct i2c_client *client,
 				     const struct i2c_device_id *id)
 {
@@ -169,6 +214,18 @@ static int bq27xxx_battery_i2c_probe(struct i2c_client *client,
 	di->bus.read_bulk = bq27xxx_battery_i2c_bulk_read;
 	di->bus.write_bulk = bq27xxx_battery_i2c_bulk_write;
 
+	/* BQ27411 and BQ27541 may be interchanged in replacement battery packs. */
+	switch (di->chip) {
+	case BQ27411:
+	case BQ27541:
+		ret = bq27xxx_battery_i2c_check_device_type(di);
+		if (ret)
+			goto err_failed;
+		break;
+	default:
+		break;
+	}
+
 	ret = bq27xxx_battery_setup(di);
 	if (ret)
 		goto err_failed;

-- 
2.56.0

Re: [PATCH v6] power: supply: bq27xxx: detect bq27541 behind bq27411 compatible

[David Heidelberg]

On 18/10/2026 23:15, Rinat Muhamedgaliev via B4 Relay wrote:
> From: Rinat Muhamedgaliev <rinat.muhamedgaliev@gmail.com>
> 
> OnePlus 6 and 6T replacement battery packs may contain either a bq27411
> or a bq27541 fuel gauge at I2C address 0x55. The device tree currently
> identifies the gauge as bq27411, but a bq27541 uses a different register
> map and then reports invalid battery values.
> 
> Read the DeviceType control subcommand when probing a bq27411. Keep the
> existing profile for DeviceType 0x0421, but select the bq27541 profile
> for DeviceType 0x0541. This retains the established DT ABI and supports
> replacement packs without introducing a generic compatible.
> 
> Tested on OnePlus 6T (fajita) with DeviceType 0x0541: voltage, state of
> charge, and temperature were reported correctly. Testing on hardware with
> DeviceType 0x0421 would be appreciated.
> 
> Signed-off-by: Rinat Muhamedgaliev <rinat.muhamedgaliev@gmail.com>
> ---
>   drivers/power/supply/bq27xxx_battery_i2c.c | 57 ++++++++++++++++++++++++++++++
>   1 file changed, 57 insertions(+)
> 
> diff --git a/drivers/power/supply/bq27xxx_battery_i2c.c b/drivers/power/supply/bq27xxx_battery_i2c.c
> index 94b00bb89c17..0b957888ad2b 100644
> --- a/drivers/power/supply/bq27xxx_battery_i2c.c
> +++ b/drivers/power/supply/bq27xxx_battery_i2c.c
> @@ -16,6 +16,11 @@
>   static DEFINE_IDR(battery_id);
>   static DEFINE_MUTEX(battery_mutex);
>   
> +#define BQ27XXX_REG_CTRL		0x00
> +#define BQ27XXX_DEVICE_TYPE		0x0001
> +#define BQ27411_DEVICE_TYPE		0x0421
> +#define BQ27541_DEVICE_TYPE		0x0541
> +
>   static irqreturn_t bq27xxx_battery_irq_handler_thread(int irq, void *data)
>   {
>   	struct bq27xxx_device_info *di = data;
> @@ -136,6 +141,46 @@ static int bq27xxx_battery_i2c_bulk_write(struct bq27xxx_device_info *di,
>   	return 0;
>   }
>   
> +static int bq27xxx_battery_i2c_check_device_type(struct bq27xxx_device_info *di)
> +{
> +	enum bq27xxx_chip detected_chip;
> +	int expected_type;
> +	int ret;
> +
> +	ret = di->bus.write(di, BQ27XXX_REG_CTRL, BQ27XXX_DEVICE_TYPE,
> +			    false);
> +	if (ret < 0)
> +		return ret;
> +
> +	ret = di->bus.read(di, BQ27XXX_REG_CTRL, false);
> +	if (ret < 0)
> +		return ret;
> +
> +	switch (ret) {
> +	case BQ27411_DEVICE_TYPE:
> +		detected_chip = BQ27411;
> +		break;
> +	case BQ27541_DEVICE_TYPE:
> +		detected_chip = BQ27541;
> +		break;
> +	default:
> +		dev_err(di->dev, "unrecognized DeviceType 0x%04x\n", ret);
> +		return -ENODEV;
> +	}
> +
> +	if (detected_chip == di->chip)
> +		return 0;
> +
> +	expected_type = di->chip == BQ27411 ? BQ27411_DEVICE_TYPE :
> +		BQ27541_DEVICE_TYPE;

This is not that generic, I would go for extensible design, something like:

switch (di->chip) {
case BQ27411:
     expected_type = BQ27411_DEVICE_TYPE
case BQ27541:
     expected_type = BQ27541_DEVICE_TYPE
default:
     dev_warn(di->dev, "expected chip undefined\n");
}


> +	dev_warn(di->dev,
> +		 "detected DeviceType 0x%04x instead of expected 0x%04x\n",
> +		 ret, expected_type);
> +	di->chip = detected_chip;
> +
> +	return 0;
> +}
> +
>   static int bq27xxx_battery_i2c_probe(struct i2c_client *client,
>   				     const struct i2c_device_id *id)
>   {
> @@ -169,6 +214,18 @@ static int bq27xxx_battery_i2c_probe(struct i2c_client *client,
>   	di->bus.read_bulk = bq27xxx_battery_i2c_bulk_read;
>   	di->bus.write_bulk = bq27xxx_battery_i2c_bulk_write;
>   
> +	/* BQ27411 and BQ27541 may be interchanged in replacement battery packs. */

We can see this from the code. The comment should imply the list should be 
extended with devices which can be detected over i2c.

For all devices supporting reporting it's ID - if we can check at boot it's 
really reporting, it brings the value - e.g. broken or different device will not 
show 0 or 100% of battery charge, but fail to load.

Otherwise IMHO looks good.
Thanks

> +	switch (di->chip) {
> +	case BQ27411:
> +	case BQ27541:
> +		ret = bq27xxx_battery_i2c_check_device_type(di);
> +		if (ret)
> +			goto err_failed;
> +		break;
> +	default:
> +		break;
> +	}
> +
>   	ret = bq27xxx_battery_setup(di);
>   	if (ret)
>   		goto err_failed;
>