The ENS210 driver uses SMBus transactions (such as byte, word, and block
data reads/writes) during the probe and measurement phases. However, the
initial functionality check only validated a subset of these capabilities,
which could lead to loading failures on adapters requiring SMBus
emulation or native-only controllers.

To ensure compatibility across a wide range of I2C adapters, modify the
functionality check to verify if the adapter supports the required native
operations or, failing that, supports the SMBus emulation layer.

Fixes: c524fbca672e ("iio: humidity: Add support for ENS210")
Signed-off-by: Salah Triki <salah.triki@gmail.com>
---
Changes since v3:
- Fixed the alignment and indentation of the I2C functionality check
  per Andy's review.

Changes since v2:
- Fixed the alignment and indentation of the I2C functionality check
  per Maxime's review.

Changes since v1:
- Updated the I2C functionality test to check for both required native
  operations and SMBus emulation (`I2C_FUNC_SMBUS_EMUL`) to prevent
  loading issues on controllers lacking the emulation flag.

 drivers/iio/humidity/ens210.c | 9 ++++++---
 1 file changed, 6 insertions(+), 3 deletions(-)

diff --git a/drivers/iio/humidity/ens210.c b/drivers/iio/humidity/ens210.c
index 77418d97f30d..96076b0391a7 100644
--- a/drivers/iio/humidity/ens210.c
+++ b/drivers/iio/humidity/ens210.c
@@ -202,9 +202,12 @@ static int ens210_probe(struct i2c_client *client)
 	int ret;
 
 	if (!i2c_check_functionality(client->adapter,
-				     I2C_FUNC_SMBUS_WRITE_BYTE_DATA |
-				     I2C_FUNC_SMBUS_WRITE_BYTE |
-				     I2C_FUNC_SMBUS_READ_I2C_BLOCK)) {
+				I2C_FUNC_SMBUS_WRITE_BYTE_DATA |
+				I2C_FUNC_SMBUS_WRITE_BYTE |
+				I2C_FUNC_SMBUS_READ_BYTE_DATA |
+				I2C_FUNC_SMBUS_READ_WORD_DATA |
+				I2C_FUNC_SMBUS_READ_I2C_BLOCK) &&
+	    !i2c_check_functionality(client->adapter, I2C_FUNC_SMBUS_EMUL)) {
 		return dev_err_probe(&client->dev, -EOPNOTSUPP,
 			"adapter does not support some i2c transactions\n");
 	}
-- 
2.43.0

On Wed, May 06, 2026 at 10:46:29AM +0100, Salah Triki wrote:
> The ENS210 driver uses SMBus transactions (such as byte, word, and block
> data reads/writes) during the probe and measurement phases. However, the
> initial functionality check only validated a subset of these capabilities,
> which could lead to loading failures on adapters requiring SMBus
> emulation or native-only controllers.
> 
> To ensure compatibility across a wide range of I2C adapters, modify the
> functionality check to verify if the adapter supports the required native
> operations or, failing that, supports the SMBus emulation layer.

...

>  	if (!i2c_check_functionality(client->adapter,

> -				     I2C_FUNC_SMBUS_WRITE_BYTE_DATA |
> -				     I2C_FUNC_SMBUS_WRITE_BYTE |
> -				     I2C_FUNC_SMBUS_READ_I2C_BLOCK)) {
> +				I2C_FUNC_SMBUS_WRITE_BYTE_DATA |
> +				I2C_FUNC_SMBUS_WRITE_BYTE |
> +				I2C_FUNC_SMBUS_READ_BYTE_DATA |
> +				I2C_FUNC_SMBUS_READ_WORD_DATA |
> +				I2C_FUNC_SMBUS_READ_I2C_BLOCK) &&

No, the above is FINE as is, you need to adjust the new added lines
accordingly.

> +	    !i2c_check_functionality(client->adapter, I2C_FUNC_SMBUS_EMUL)) {
>  		return dev_err_probe(&client->dev, -EOPNOTSUPP,
>  			"adapter does not support some i2c transactions\n");
>  	}

-- 
With Best Regards,
Andy Shevchenko