Re: [PATCH] iio: gyro: mpu3050: fix sign of raw angular velocity readings

On 8/2/26 1:55 AM, Cong Nguyen wrote:
> The MPU-3050 gyroscope output registers hold 16-bit two's complement
> values; the angular velocity channels are declared with .sign = 's'.
> When mpu3050_read_raw() handles IIO_CHAN_INFO_RAW it reads the register
> via a big-endian regmap_bulk_read() and assigns it with:
> 
> 	*val = be16_to_cpu(raw_val);
> 
> be16_to_cpu() yields an unsigned 16-bit quantity, so negative rates
> (bit 15 set) are reported to userspace as large positive integers
> (e.g. -1 becomes 65535) instead of the correct negative value.
> 
> Cast to s16 before the assignment, matching the temperature channel a
> few lines above which already handles the sign correctly.
> 
> Fixes: 3904b28efb2c ("iio: gyro: Add driver for the MPU-3050 gyroscope")
> Cc: [email protected]
> Assisted-by: Claude:claude-opus-4
> Signed-off-by: Cong Nguyen <[email protected]>
> ---
>  drivers/iio/gyro/mpu3050-core.c | 2 +-
>  1 file changed, 1 insertion(+), 1 deletion(-)
> 
> diff --git a/drivers/iio/gyro/mpu3050-core.c b/drivers/iio/gyro/mpu3050-core.c
> index d84e04e4b431..07c0f9011c63 100644
> --- a/drivers/iio/gyro/mpu3050-core.c
> +++ b/drivers/iio/gyro/mpu3050-core.c
> @@ -356,7 +356,7 @@ static int mpu3050_read_raw(struct iio_dev *indio_dev,
>  				goto out_read_raw_unlock;
>  			}
>  
> -			*val = be16_to_cpu(raw_val);
> +			*val = (s16)be16_to_cpu(raw_val);
>  			ret = IIO_VAL_INT;
>  
>  			goto out_read_raw_unlock;

Usually, we use sign_extend32() instead of a cast for this. But this
driver already has a similar cast for the temperature channel. So to
keep it consistent, this looks fine.

Reviewed-by: David Lechner <[email protected]>