[PATCH] iio: light: opt4001: Fix a wrong array iteration limit

[PATCH] iio: light: opt4001: Fix a wrong array iteration limit

[Jonathan Cameron]

From: Jonathan Cameron <Jonathan.Cameron@huawei.com>

In practice it's unlikely anyone would try to set the integration time
to 0 which isn't in the available list and if they did then they would
get index 12 which whilst reserved on the device fits in the field.
However a compiler might get half way through this reasoning and that
might be the cause of

> >> drivers/iio/light/opt4001.c:215:9: error: call to '__compiletime_assert_355' declared with 'error' attribute: FIELD_PREP: value too large for the field
>      215 |         reg |= FIELD_PREP(OPT4001_CTRL_CONV_TIME_MASK, chip->int_time);

Even if this isn't the cause, it looks like a bug to me.

Fixes: 9a9608418292 ("iio: light: Add support for TI OPT4001 light sensor")
Reported-by: kernel test robot <lkp@intel.com>
Closes: https://lore.kernel.org/oe-kbuild-all/202308061902.0gVz6bSe-lkp@intel.com/
Cc: Stefan Windfeldt-Prytz <stefan.windfeldt-prytz@axis.com>
Signed-off-by: Jonathan Cameron <Jonathan.Cameron@huawei.com>
---
 drivers/iio/light/opt4001.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/drivers/iio/light/opt4001.c b/drivers/iio/light/opt4001.c
index 502946bf9f94..83f978706758 100644
--- a/drivers/iio/light/opt4001.c
+++ b/drivers/iio/light/opt4001.c
@@ -137,7 +137,7 @@ static int opt4001_als_time_to_index(const u32 als_integration_time)
 {
 	int i;
 
-	for (i = 0; i < ARRAY_SIZE(opt4001_int_time_available); i++) {
+	for (i = 0; i < ARRAY_SIZE(opt4001_int_time_available) / 2; i++) {
 		if (als_integration_time == opt4001_int_time_available[i][1])
 			return i;
 	}
-- 
2.41.0

Re: [PATCH] iio: light: opt4001: Fix a wrong array iteration limit

[Jonathan Cameron]

On Mon,  7 Aug 2023 20:50:43 +0100
Jonathan Cameron <jic23@kernel.org> wrote:

> From: Jonathan Cameron <Jonathan.Cameron@huawei.com>
> 
> In practice it's unlikely anyone would try to set the integration time
> to 0 which isn't in the available list and if they did then they would
> get index 12 which whilst reserved on the device fits in the field.
> However a compiler might get half way through this reasoning and that
> might be the cause of
> 
> > >> drivers/iio/light/opt4001.c:215:9: error: call to '__compiletime_assert_355' declared with 'error' attribute: FIELD_PREP: value too large for the field  
> >      215 |         reg |= FIELD_PREP(OPT4001_CTRL_CONV_TIME_MASK, chip->int_time);  
> 
> Even if this isn't the cause, it looks like a bug to me.
> 
> Fixes: 9a9608418292 ("iio: light: Add support for TI OPT4001 light sensor")
> Reported-by: kernel test robot <lkp@intel.com>
> Closes: https://lore.kernel.org/oe-kbuild-all/202308061902.0gVz6bSe-lkp@intel.com/
> Cc: Stefan Windfeldt-Prytz <stefan.windfeldt-prytz@axis.com>
> Signed-off-by: Jonathan Cameron <Jonathan.Cameron@huawei.com>

Oops. Clearly half asleep last night. This is garbage so I'm back to the drawing board
on what is causing clang to believe int_time can be bigger than 4 bits.

Any suggestions welcome!

> ---
>  drivers/iio/light/opt4001.c | 2 +-
>  1 file changed, 1 insertion(+), 1 deletion(-)
> 
> diff --git a/drivers/iio/light/opt4001.c b/drivers/iio/light/opt4001.c
> index 502946bf9f94..83f978706758 100644
> --- a/drivers/iio/light/opt4001.c
> +++ b/drivers/iio/light/opt4001.c
> @@ -137,7 +137,7 @@ static int opt4001_als_time_to_index(const u32 als_integration_time)
>  {
>  	int i;
>  
> -	for (i = 0; i < ARRAY_SIZE(opt4001_int_time_available); i++) {
> +	for (i = 0; i < ARRAY_SIZE(opt4001_int_time_available) / 2; i++) {
>  		if (als_integration_time == opt4001_int_time_available[i][1])
>  			return i;
>  	}