* [PATCH v2] iio: bmp280: fix compensation of humidity
@ 2020-04-29 18:48 Andreas Klinger
2020-05-03 13:05 ` Jonathan Cameron
0 siblings, 1 reply; 2+ messages in thread
From: Andreas Klinger @ 2020-04-29 18:48 UTC (permalink / raw)
To: jic23
Cc: knaack.h, lars, pmeerw, bgolaszewski, linus.walleij, tglx,
allison, linux-iio, linux-kernel
Output of humidity compensation is limited to the range between 0 and
100 percent. Add this to the compensation formula as described in the
datasheet chapter 4.2.3.
Change to v1:
Thanks to Tomasz for suggesting the easier to use function clamp_val()
which is now used.
Signed-off-by: Andreas Klinger <ak@it-klinger.de>
---
drivers/iio/pressure/bmp280-core.c | 2 ++
1 file changed, 2 insertions(+)
diff --git a/drivers/iio/pressure/bmp280-core.c b/drivers/iio/pressure/bmp280-core.c
index 29c209cc1108..297ee2205bf6 100644
--- a/drivers/iio/pressure/bmp280-core.c
+++ b/drivers/iio/pressure/bmp280-core.c
@@ -271,6 +271,8 @@ static u32 bmp280_compensate_humidity(struct bmp280_data *data,
+ (s32)2097152) * calib->H2 + 8192) >> 14);
var -= ((((var >> 15) * (var >> 15)) >> 7) * (s32)calib->H1) >> 4;
+ var = clamp_val(var, 0, 419430400);
+
return var >> 12;
};
--
2.20.1
^ permalink raw reply related [flat|nested] 2+ messages in thread
* Re: [PATCH v2] iio: bmp280: fix compensation of humidity
2020-04-29 18:48 [PATCH v2] iio: bmp280: fix compensation of humidity Andreas Klinger
@ 2020-05-03 13:05 ` Jonathan Cameron
0 siblings, 0 replies; 2+ messages in thread
From: Jonathan Cameron @ 2020-05-03 13:05 UTC (permalink / raw)
To: Andreas Klinger
Cc: knaack.h, lars, pmeerw, bgolaszewski, linus.walleij, tglx,
allison, linux-iio, linux-kernel
On Wed, 29 Apr 2020 20:48:54 +0200
Andreas Klinger <ak@it-klinger.de> wrote:
> Output of humidity compensation is limited to the range between 0 and
> 100 percent. Add this to the compensation formula as described in the
> datasheet chapter 4.2.3.
More details needed...
1. Fixes tag
2. What is the result of this not being clamped? What happens if I set
a value outside that range?
>
> Change to v1:
> Thanks to Tomasz for suggesting the easier to use function clamp_val()
> which is now used.
Change log belongs below the ---
>
> Signed-off-by: Andreas Klinger <ak@it-klinger.de>
> ---
Here for changelog.
> drivers/iio/pressure/bmp280-core.c | 2 ++
> 1 file changed, 2 insertions(+)
>
> diff --git a/drivers/iio/pressure/bmp280-core.c b/drivers/iio/pressure/bmp280-core.c
> index 29c209cc1108..297ee2205bf6 100644
> --- a/drivers/iio/pressure/bmp280-core.c
> +++ b/drivers/iio/pressure/bmp280-core.c
> @@ -271,6 +271,8 @@ static u32 bmp280_compensate_humidity(struct bmp280_data *data,
> + (s32)2097152) * calib->H2 + 8192) >> 14);
> var -= ((((var >> 15) * (var >> 15)) >> 7) * (s32)calib->H1) >> 4;
>
> + var = clamp_val(var, 0, 419430400);
> +
> return var >> 12;
> };
>
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