[PATCH v2] iio: dac: m62332: Fix regulator reference count imbalance

[PATCH v2] iio: dac: m62332: Fix regulator reference count imbalance

[Erick Henrique]

m62332_set_value() enables the Vcc regulator on every write of a
non-zero value and disables it on every write of zero, without tracking
the channel's current state. Because the regulator is reference counted,
changing a channel directly from one non-zero value to another enables
it more than once, while a later write of zero disables it only once.
The reference count never returns to zero and the regulator is left
enabled indefinitely.

Only enable the regulator on the transition from zero to non-zero, and
only disable it on the transition from non-zero to zero, using the
previously stored channel value to detect the edge. Balance the
regulator on the I2C error path so the reference count stays consistent
if the write fails.

Fixes: b87b0c0f81e8 ("iio: add m62332 DAC driver")
Reported-by: Sashiko <sashiko-bot@kernel.org>
Closes: https://sashiko.dev/#/patchset/20260418130322.106769-1-erick.henrique.rodrigues%40usp.br
Cc: stable@vger.kernel.org
Signed-off-by: Erick Henrique <erick.henrique.rodrigues@usp.br>
---
v2:
- Use local enabling/disabling booleans for the edge conditions (Jonathan)
- Credit Sashiko directly in Reported-by with a Closes: link to its
  report entry, per Jonathan
v1: https://lore.kernel.org/r/20260630021309.36636-1-erick.henrique.rodrigues@usp.br

 drivers/iio/dac/m62332.c | 17 ++++++++++++-----
 1 file changed, 12 insertions(+), 5 deletions(-)

diff --git a/drivers/iio/dac/m62332.c b/drivers/iio/dac/m62332.c
index 3497513854d7..2c13feee8d61 100644
--- a/drivers/iio/dac/m62332.c
+++ b/drivers/iio/dac/m62332.c
@@ -32,6 +32,7 @@ static int m62332_set_value(struct iio_dev *indio_dev, u8 val, int channel)
 {
 	struct m62332_data *data = iio_priv(indio_dev);
 	struct i2c_client *client = data->client;
+	bool enabling, disabling;
 	u8 outbuf[2];
 	int res;
 
@@ -43,7 +44,10 @@ static int m62332_set_value(struct iio_dev *indio_dev, u8 val, int channel)
 
 	mutex_lock(&data->mutex);
 
-	if (val) {
+	enabling = val && !data->raw[channel];
+	disabling = !val && data->raw[channel];
+
+	if (enabling) {
 		res = regulator_enable(data->vcc);
 		if (res)
 			goto out;
@@ -52,14 +56,17 @@ static int m62332_set_value(struct iio_dev *indio_dev, u8 val, int channel)
 	res = i2c_master_send(client, outbuf, ARRAY_SIZE(outbuf));
 	if (res >= 0 && res != ARRAY_SIZE(outbuf))
 		res = -EIO;
-	if (res < 0)
+	if (res < 0) {
+		if (enabling)
+			regulator_disable(data->vcc);
 		goto out;
+	}
 
-	data->raw[channel] = val;
-
-	if (!val)
+	if (disabling)
 		regulator_disable(data->vcc);
 
+	data->raw[channel] = val;
+
 	mutex_unlock(&data->mutex);
 
 	return 0;
-- 
2.51.0

Re: [PATCH v2] iio: dac: m62332: Fix regulator reference count imbalance

[Jonathan Cameron]

On Fri,  3 Jul 2026 17:52:36 -0300
Erick Henrique <erick.henrique.rodrigues@usp.br> wrote:

> m62332_set_value() enables the Vcc regulator on every write of a
> non-zero value and disables it on every write of zero, without tracking
> the channel's current state. Because the regulator is reference counted,
> changing a channel directly from one non-zero value to another enables
> it more than once, while a later write of zero disables it only once.
> The reference count never returns to zero and the regulator is left
> enabled indefinitely.
> 
> Only enable the regulator on the transition from zero to non-zero, and
> only disable it on the transition from non-zero to zero, using the
> previously stored channel value to detect the edge. Balance the
> regulator on the I2C error path so the reference count stays consistent
> if the write fails.
> 
> Fixes: b87b0c0f81e8 ("iio: add m62332 DAC driver")
> Reported-by: Sashiko <sashiko-bot@kernel.org>
> Closes: https://sashiko.dev/#/patchset/20260418130322.106769-1-erick.henrique.rodrigues%40usp.br
> Cc: stable@vger.kernel.org
> Signed-off-by: Erick Henrique <erick.henrique.rodrigues@usp.br>
Applied to the fixes-togreg branch of iio.git

Thanks,

Jonathan

> ---
> v2:
> - Use local enabling/disabling booleans for the edge conditions (Jonathan)
> - Credit Sashiko directly in Reported-by with a Closes: link to its
>   report entry, per Jonathan
> v1: https://lore.kernel.org/r/20260630021309.36636-1-erick.henrique.rodrigues@usp.br
> 
>  drivers/iio/dac/m62332.c | 17 ++++++++++++-----
>  1 file changed, 12 insertions(+), 5 deletions(-)
> 
> diff --git a/drivers/iio/dac/m62332.c b/drivers/iio/dac/m62332.c
> index 3497513854d7..2c13feee8d61 100644
> --- a/drivers/iio/dac/m62332.c
> +++ b/drivers/iio/dac/m62332.c
> @@ -32,6 +32,7 @@ static int m62332_set_value(struct iio_dev *indio_dev, u8 val, int channel)
>  {
>  	struct m62332_data *data = iio_priv(indio_dev);
>  	struct i2c_client *client = data->client;
> +	bool enabling, disabling;
>  	u8 outbuf[2];
>  	int res;
>  
> @@ -43,7 +44,10 @@ static int m62332_set_value(struct iio_dev *indio_dev, u8 val, int channel)
>  
>  	mutex_lock(&data->mutex);
>  
> -	if (val) {
> +	enabling = val && !data->raw[channel];
> +	disabling = !val && data->raw[channel];
> +
> +	if (enabling) {
>  		res = regulator_enable(data->vcc);
>  		if (res)
>  			goto out;
> @@ -52,14 +56,17 @@ static int m62332_set_value(struct iio_dev *indio_dev, u8 val, int channel)
>  	res = i2c_master_send(client, outbuf, ARRAY_SIZE(outbuf));
>  	if (res >= 0 && res != ARRAY_SIZE(outbuf))
>  		res = -EIO;
> -	if (res < 0)
> +	if (res < 0) {
> +		if (enabling)
> +			regulator_disable(data->vcc);
>  		goto out;
> +	}
>  
> -	data->raw[channel] = val;
> -
> -	if (!val)
> +	if (disabling)
>  		regulator_disable(data->vcc);
>  
> +	data->raw[channel] = val;
> +
>  	mutex_unlock(&data->mutex);
>  
>  	return 0;