[PATCH] iio: adc: mt6359: fix unchecked return value in mt6358_read_imp

[PATCH] iio: adc: mt6359: fix unchecked return value in mt6358_read_imp

[Salah Triki]

In mt6358_read_imp(), the return value of regmap_read() is currently
ignored. This is problematic because if the bus read fails the variable
val_v remains uninitialized.

The function subsequently assigns this uninitialized stack value to
*vbat, leading to incorrect measurement results being reported to
the IIO subsystem without any error indication.

Update the function to check the return value of regmap_read(). Ensure
that mt6358_stop_imp_conv() is still called to clean up the hardware
state before returning the error code.

Signed-off-by: Salah Triki <salah.triki@gmail.com>
---
 drivers/iio/adc/mt6359-auxadc.c | 5 ++++-
 1 file changed, 4 insertions(+), 1 deletion(-)

diff --git a/drivers/iio/adc/mt6359-auxadc.c b/drivers/iio/adc/mt6359-auxadc.c
index 6b9ed9b1fde2..f927bff4a26a 100644
--- a/drivers/iio/adc/mt6359-auxadc.c
+++ b/drivers/iio/adc/mt6359-auxadc.c
@@ -497,10 +497,13 @@ static int mt6358_read_imp(struct mt6359_auxadc *adc_dev,
 		return ret;
 
 	/* Read the params before stopping */
-	regmap_read(regmap, reg_adc0 + (cinfo->imp_adc_num << 1), &val_v);
+	ret = regmap_read(regmap, reg_adc0 + (cinfo->imp_adc_num << 1), &val_v);
 
 	mt6358_stop_imp_conv(adc_dev);
 
+	if (ret)
+		return ret;
+
 	if (vbat)
 		*vbat = val_v;
 	if (ibat)
-- 
2.43.0

Re: [PATCH] iio: adc: mt6359: fix unchecked return value in mt6358_read_imp

[Andy Shevchenko]

On Mon, Apr 27, 2026 at 09:54:57AM +0100, Salah Triki wrote:
> In mt6358_read_imp(), the return value of regmap_read() is currently
> ignored. This is problematic because if the bus read fails the variable
> val_v remains uninitialized.
> 
> The function subsequently assigns this uninitialized stack value to
> *vbat, leading to incorrect measurement results being reported to
> the IIO subsystem without any error indication.
> 
> Update the function to check the return value of regmap_read(). Ensure
> that mt6358_stop_imp_conv() is still called to clean up the hardware
> state before returning the error code.

Sounds like this deserves a Fixes tag, but the problem is that the whole driver
is written like this. Why does having this fixed make it special?

-- 
With Best Regards,
Andy Shevchenko

Re: [PATCH] iio: adc: mt6359: fix unchecked return value in mt6358_read_imp

[Salah Triki]

On Mon, Apr 27, 2026 at 12:14:40PM +0300, Andy Shevchenko wrote:
> On Mon, Apr 27, 2026 at 09:54:57AM +0100, Salah Triki wrote:
> > In mt6358_read_imp(), the return value of regmap_read() is currently
> > ignored. This is problematic because if the bus read fails the variable
> > val_v remains uninitialized.
> > 
> > The function subsequently assigns this uninitialized stack value to
> > *vbat, leading to incorrect measurement results being reported to
> > the IIO subsystem without any error indication.
> > 
> > Update the function to check the return value of regmap_read(). Ensure
> > that mt6358_stop_imp_conv() is still called to clean up the hardware
> > state before returning the error code.
> 
> Sounds like this deserves a Fixes tag, but the problem is that the whole driver
> is written like this. Why does having this fixed make it special?
> 
> -- 
> With Best Regards,
> Andy Shevchenko
> 
> 

You are right, Andy. I noticed that several other functions in this driver
share the same issue. I will send a V2 that addresses all unchecked
regmap_read() calls in this file and I will include the Fixes tag. Thanks
for the feedback.

Best Regards
Salah Triki

[PATCH] iio: adc: mt6359: fix unchecked return value in mt6358_read_imp

[Salah Triki]

In mt6358_read_imp(), the return value of regmap_read() is currently
ignored. This is problematic because if the bus read fails the variable
val_v remains uninitialized.

The function subsequently assigns this uninitialized stack value to
*vbat, leading to incorrect measurement results being reported to
the IIO subsystem without any error indication.

Update the function to check the return value of regmap_read(). Ensure
that mt6358_stop_imp_conv() is still called to clean up the hardware
state before returning the error code.

Fixes: 3587914bf61 ("iio: adc: Add support for MediaTek MT6357/8/9 Auxiliary ADC")
Signed-off-by: Salah Triki <salah.triki@gmail.com>
---
Changes in v2:
- Added Fixes tag.
- Re-examined the entire driver for unchecked regmap operations.
  While several regmap_write() and regmap_set_bits() calls also ignore
  return values, I focused on this specific regmap_read() in 
  mt6358_read_imp() because it leads to an uninitialized variable usage
  (val_v). This makes this fix critical for reporting correct data 
  to userspace.

 drivers/iio/adc/mt6359-auxadc.c | 5 ++++-
 1 file changed, 4 insertions(+), 1 deletion(-)

diff --git a/drivers/iio/adc/mt6359-auxadc.c b/drivers/iio/adc/mt6359-auxadc.c
index 6b9ed9b1fde2..f927bff4a26a 100644
--- a/drivers/iio/adc/mt6359-auxadc.c
+++ b/drivers/iio/adc/mt6359-auxadc.c
@@ -497,10 +497,13 @@ static int mt6358_read_imp(struct mt6359_auxadc *adc_dev,
 		return ret;
 
 	/* Read the params before stopping */
-	regmap_read(regmap, reg_adc0 + (cinfo->imp_adc_num << 1), &val_v);
+	ret = regmap_read(regmap, reg_adc0 + (cinfo->imp_adc_num << 1), &val_v);
 
 	mt6358_stop_imp_conv(adc_dev);
 
+	if (ret)
+		return ret;
+
 	if (vbat)
 		*vbat = val_v;
 	if (ibat)
-- 
2.43.0