[PATCH] media: i2c: imx296: Fix error handling while reading temperature

[PATCH] media: i2c: imx296: Fix error handling while reading temperature

[Christophe JAILLET]

If imx296_read() returns an error, its returned value is a negative value.
But because of the "& IMX296_TMDOUT_MASK" (i.e. 0x3ff), 'tmdout' can't be
negative.

So the error handling does not work as expected and a wrong value is used
to compute the temperature.

Apply the IMX296_TMDOUT_MASK mask after checking for errors to fix it.

Fixes: cb33db2b6ccf ("media: i2c: IMX296 camera sensor driver")
Signed-off-by: Christophe JAILLET <christophe.jaillet@wanadoo.fr>
---
 drivers/media/i2c/imx296.c | 4 +++-
 1 file changed, 3 insertions(+), 1 deletion(-)

diff --git a/drivers/media/i2c/imx296.c b/drivers/media/i2c/imx296.c
index 4f22c0515ef8..c3d6d52fc772 100644
--- a/drivers/media/i2c/imx296.c
+++ b/drivers/media/i2c/imx296.c
@@ -922,10 +922,12 @@ static int imx296_read_temperature(struct imx296 *sensor, int *temp)
 	if (ret < 0)
 		return ret;
 
-	tmdout = imx296_read(sensor, IMX296_TMDOUT) & IMX296_TMDOUT_MASK;
+	tmdout = imx296_read(sensor, IMX296_TMDOUT);
 	if (tmdout < 0)
 		return tmdout;
 
+	tmdout &= IMX296_TMDOUT_MASK;
+
 	/* T(°C) = 246.312 - 0.304 * TMDOUT */;
 	*temp = 246312 - 304 * tmdout;
 
-- 
2.34.1

Re: [PATCH] media: i2c: imx296: Fix error handling while reading temperature

[Laurent Pinchart]

Hi Christophe,

Thank you for the patch.

On Mon, Apr 17, 2023 at 12:14:42AM +0200, Christophe JAILLET wrote:
> If imx296_read() returns an error, its returned value is a negative value.
> But because of the "& IMX296_TMDOUT_MASK" (i.e. 0x3ff), 'tmdout' can't be
> negative.
> 
> So the error handling does not work as expected and a wrong value is used
> to compute the temperature.
> 
> Apply the IMX296_TMDOUT_MASK mask after checking for errors to fix it.
> 
> Fixes: cb33db2b6ccf ("media: i2c: IMX296 camera sensor driver")
> Signed-off-by: Christophe JAILLET <christophe.jaillet@wanadoo.fr>

Dan Carpenter has submitted the same fix in
https://lore.kernel.org/linux-media/Y%2FYf19AE78jn5YW7@kili/. Sakari,
could you please pick it up ?

> ---
>  drivers/media/i2c/imx296.c | 4 +++-
>  1 file changed, 3 insertions(+), 1 deletion(-)
> 
> diff --git a/drivers/media/i2c/imx296.c b/drivers/media/i2c/imx296.c
> index 4f22c0515ef8..c3d6d52fc772 100644
> --- a/drivers/media/i2c/imx296.c
> +++ b/drivers/media/i2c/imx296.c
> @@ -922,10 +922,12 @@ static int imx296_read_temperature(struct imx296 *sensor, int *temp)
>  	if (ret < 0)
>  		return ret;
>  
> -	tmdout = imx296_read(sensor, IMX296_TMDOUT) & IMX296_TMDOUT_MASK;
> +	tmdout = imx296_read(sensor, IMX296_TMDOUT);
>  	if (tmdout < 0)
>  		return tmdout;
>  
> +	tmdout &= IMX296_TMDOUT_MASK;
> +
>  	/* T(°C) = 246.312 - 0.304 * TMDOUT */;
>  	*temp = 246312 - 304 * tmdout;
>  

-- 
Regards,

Laurent Pinchart

Re: [PATCH] media: i2c: imx296: Fix error handling while reading temperature

[Sakari Ailus]

Hi Laurent,

On Mon, Apr 17, 2023 at 08:30:59AM +0300, Laurent Pinchart wrote:
> Hi Christophe,
> 
> Thank you for the patch.
> 
> On Mon, Apr 17, 2023 at 12:14:42AM +0200, Christophe JAILLET wrote:
> > If imx296_read() returns an error, its returned value is a negative value.
> > But because of the "& IMX296_TMDOUT_MASK" (i.e. 0x3ff), 'tmdout' can't be
> > negative.
> > 
> > So the error handling does not work as expected and a wrong value is used
> > to compute the temperature.
> > 
> > Apply the IMX296_TMDOUT_MASK mask after checking for errors to fix it.
> > 
> > Fixes: cb33db2b6ccf ("media: i2c: IMX296 camera sensor driver")
> > Signed-off-by: Christophe JAILLET <christophe.jaillet@wanadoo.fr>
> 
> Dan Carpenter has submitted the same fix in
> https://lore.kernel.org/linux-media/Y%2FYf19AE78jn5YW7@kili/. Sakari,
> could you please pick it up ?

Oops, thanks for notifying me. This slipped from my hands somehow. It's in
my tree now.

-- 
Sakari Ailus