[PATCH 0/2] Subject: [PATCH 0/2] iio: light: cm3323: fix and cleanup

[PATCH 0/2] Subject: [PATCH 0/2] iio: light: cm3323: fix and cleanup

[Aldo Conte]

This series fixes a bug and does a cleanup of the CM3323 
color light sensor driver.

Patch 1 fixes data->reg_conf being incorrectly initialized with the 
return value of the i2c_smbus_write_word_data() instead of the actual 	
register value. Tested with i2c-stub on a Raspberri Pi 3B.

Patch 2 converts dev_err() to dev_err_probe() in the probe path.


Aldo Conte (2):
  iio: light: cm3323: fix reg_conf not being initialized correctly
  iio: light: cm3323: use dev_err_probe() in probe path

 drivers/iio/light/cm3323.c | 24 ++++++++++--------------
 1 file changed, 10 insertions(+), 14 deletions(-)

-- 
2.53.0

[PATCH 1/2] iio: light: cm3323: fix reg_conf not being initialized correctly

[Aldo Conte]

The code stores the return value of i2c_smbus_write_word_data()
in data->reg_conf; however, this value represents the result
of the write operation and not the value actually written to
the configuration register. This meant that the contents of
data->reg_conf did not truly reflect the contents
of the hardware register.

Instead, save the value of the register before the write
and use this value in the I2C write.

The bug was found by code inspection: i2c_smbus_write_word_data()
returns 0 on success, not the value written to the register.

Tested using i2c-stub on a Raspberry Pi 3B running a custom 6.19.10
kernel. Before loading the driver , the configuration register 0x00
CM3323_CMD_CONF was populated with 0x0030 using
i2cset -y 11 0x10 0x00 0x0030 w, encoding an integration time of 320ms
in bits[6:4].

Due to the error into the initialization of data->reg_conf in
cm3323_init(), the print of integration_time returns 0.040000
instead of the expected 0.320000. This happens because the read of the
integration_time depends on cm3323_get_it_bits() that is based on the
value of data->reg_conf, which is erroneously set to 0.

With this fix applied, data->reg_conf correctly saves 0x0030 after init
and the successive integration_time reports 0.320000 as expected.

Fixes: 8b0544263761 ("iio: light: Add support for Capella CM3323 color sensor")
Signed-off-by: Aldo Conte <aldocontelk@gmail.com>
---
 drivers/iio/light/cm3323.c | 5 ++---
 1 file changed, 2 insertions(+), 3 deletions(-)

diff --git a/drivers/iio/light/cm3323.c b/drivers/iio/light/cm3323.c
index 79ad6e2209ca..0fe61b8a7029 100644
--- a/drivers/iio/light/cm3323.c
+++ b/drivers/iio/light/cm3323.c
@@ -89,15 +89,14 @@ static int cm3323_init(struct iio_dev *indio_dev)
 
 	/* enable sensor and set auto force mode */
 	ret &= ~(CM3323_CONF_SD_BIT | CM3323_CONF_AF_BIT);
+	data->reg_conf = ret;
 
-	ret = i2c_smbus_write_word_data(data->client, CM3323_CMD_CONF, ret);
+	ret = i2c_smbus_write_word_data(data->client, CM3323_CMD_CONF, data->reg_conf);
 	if (ret < 0) {
 		dev_err(&data->client->dev, "Error writing reg_conf\n");
 		return ret;
 	}
 
-	data->reg_conf = ret;
-
 	return 0;
 }
 
-- 
2.53.0

[PATCH 2/2] iio: light: cm3323: use dev_err_probe() in probe path

[Aldo Conte]

Replace dev_err() calls with dev_err_probe() in cm3323_init() and
cm3323_probe(). cm3323_init() is called by cm3323_probe() ,  so using
dev_err_probe() ensures that deferred probing is handled
correctly and simplifies error paths.

Remove the redundant error message in cm3323_probe().

Tested on a Raspberry Pi 3B using i2c-stub. The driver probes
successfully and successfully read integration_time after this change.

Signed-off-by: Aldo Conte <aldocontelk@gmail.com>
---
 drivers/iio/light/cm3323.c | 19 ++++++++-----------
 1 file changed, 8 insertions(+), 11 deletions(-)

diff --git a/drivers/iio/light/cm3323.c b/drivers/iio/light/cm3323.c
index 0fe61b8a7029..43c2929fc724 100644
--- a/drivers/iio/light/cm3323.c
+++ b/drivers/iio/light/cm3323.c
@@ -82,20 +82,18 @@ static int cm3323_init(struct iio_dev *indio_dev)
 	struct cm3323_data *data = iio_priv(indio_dev);
 
 	ret = i2c_smbus_read_word_data(data->client, CM3323_CMD_CONF);
-	if (ret < 0) {
-		dev_err(&data->client->dev, "Error reading reg_conf\n");
-		return ret;
-	}
+	if (ret < 0)
+		return dev_err_probe(&data->client->dev, ret,
+				     "Error reading reg_conf\n");
 
 	/* enable sensor and set auto force mode */
 	ret &= ~(CM3323_CONF_SD_BIT | CM3323_CONF_AF_BIT);
 	data->reg_conf = ret;
 
 	ret = i2c_smbus_write_word_data(data->client, CM3323_CMD_CONF, data->reg_conf);
-	if (ret < 0) {
-		dev_err(&data->client->dev, "Error writing reg_conf\n");
-		return ret;
-	}
+	if (ret < 0)
+		return dev_err_probe(&data->client->dev, ret,
+				     "Error writing reg_conf\n");
 
 	return 0;
 }
@@ -236,10 +234,9 @@ static int cm3323_probe(struct i2c_client *client)
 	indio_dev->modes = INDIO_DIRECT_MODE;
 
 	ret = cm3323_init(indio_dev);
-	if (ret < 0) {
-		dev_err(&client->dev, "cm3323 chip init failed\n");
+	if (ret < 0)
 		return ret;
-	}
+
 
 	ret = devm_add_action_or_reset(&client->dev, cm3323_disable, indio_dev);
 	if (ret < 0)
-- 
2.53.0

Re: [PATCH 2/2] iio: light: cm3323: use dev_err_probe() in probe path

[Andy Shevchenko]

On Thu, Apr 02, 2026 at 05:17:30PM +0200, Aldo Conte wrote:
> Replace dev_err() calls with dev_err_probe() in cm3323_init() and
> cm3323_probe(). cm3323_init() is called by cm3323_probe() ,  so using
> dev_err_probe() ensures that deferred probing is handled
> correctly and simplifies error paths.
> 
> Remove the redundant error message in cm3323_probe().
> 
> Tested on a Raspberry Pi 3B using i2c-stub. The driver probes
> successfully and successfully read integration_time after this change.

...

> +		return dev_err_probe(&data->client->dev, ret,
> +				     "Error reading reg_conf\n");

Add

	struct device *dev = &data->client->dev;

at the top of the function and make these just to be one-liners.

-- 
With Best Regards,
Andy Shevchenko

Re: [PATCH 1/2] iio: light: cm3323: fix reg_conf not being initialized correctly

[Andy Shevchenko]

On Thu, Apr 02, 2026 at 05:17:29PM +0200, Aldo Conte wrote:
> The code stores the return value of i2c_smbus_write_word_data()
> in data->reg_conf; however, this value represents the result
> of the write operation and not the value actually written to
> the configuration register. This meant that the contents of
> data->reg_conf did not truly reflect the contents
> of the hardware register.
> 
> Instead, save the value of the register before the write
> and use this value in the I2C write.
> 
> The bug was found by code inspection: i2c_smbus_write_word_data()
> returns 0 on success, not the value written to the register.

> Tested using i2c-stub on a Raspberry Pi 3B running a custom 6.19.10
> kernel. Before loading the driver , the configuration register 0x00

Extra space needs to be removed.

> CM3323_CMD_CONF was populated with 0x0030 using
> i2cset -y 11 0x10 0x00 0x0030 w, encoding an integration time of 320ms

I recommend to use backquotes when providing a shell commands.

`i2cset -y 11 0x10 0x00 0x0030 w`

> in bits[6:4].
> 
> Due to the error into the initialization of data->reg_conf in
> cm3323_init(), the print of integration_time returns 0.040000
> instead of the expected 0.320000. This happens because the read of the
> integration_time depends on cm3323_get_it_bits() that is based on the
> value of data->reg_conf, which is erroneously set to 0.
> 
> With this fix applied, data->reg_conf correctly saves 0x0030 after init
> and the successive integration_time reports 0.320000 as expected.

Overall a good catch!

-- 
With Best Regards,
Andy Shevchenko