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SubjectRe: [v3,1/3] hwmon: ltc2990: refactor value conversion
On Mon, Jul 03, 2017 at 06:28:58AM +0200, Tom Levens wrote:
> Conversion from raw values to signed integers has been refactored using
> bitops.h. This also fixes a bug where negative temperatures were
> converted incorrectly.
>

Documentation/process/submitting-patches.rst, chapter 2: "Solve only one
problem per patch.".

I can understand the urge to merge two sets of changes here. However,
that creates a problem for me: The fix should be applied to stable kernels,
but not the refactoring.

Please split the patch in two, one for the bug fix and one for the
refactoring.

Thanks,
Guenter

> Signed-off-by: Tom Levens <tom.levens@cern.ch>
> ---
> drivers/hwmon/ltc2990.c | 18 ++++--------------
> 1 file changed, 4 insertions(+), 14 deletions(-)
>
> diff --git a/drivers/hwmon/ltc2990.c b/drivers/hwmon/ltc2990.c
> index 8f8fe05..e320d21 100644
> --- a/drivers/hwmon/ltc2990.c
> +++ b/drivers/hwmon/ltc2990.c
> @@ -11,6 +11,7 @@
> * the chip's internal temperature and Vcc power supply voltage.
> */
>
> +#include <linux/bitops.h>
> #include <linux/err.h>
> #include <linux/hwmon.h>
> #include <linux/hwmon-sysfs.h>
> @@ -34,15 +35,6 @@
> #define LTC2990_CONTROL_MODE_CURRENT 0x06
> #define LTC2990_CONTROL_MODE_VOLTAGE 0x07
>
> -/* convert raw register value to sign-extended integer in 16-bit range */
> -static int ltc2990_voltage_to_int(int raw)
> -{
> - if (raw & BIT(14))
> - return -(0x4000 - (raw & 0x3FFF)) << 2;
> - else
> - return (raw & 0x3FFF) << 2;
> -}
> -
> /* Return the converted value from the given register in uV or mC */
> static int ltc2990_get_value(struct i2c_client *i2c, u8 reg, int *result)
> {
> @@ -55,18 +47,16 @@ static int ltc2990_get_value(struct i2c_client *i2c, u8 reg, int *result)
> switch (reg) {
> case LTC2990_TINT_MSB:
> /* internal temp, 0.0625 degrees/LSB, 13-bit */
> - val = (val & 0x1FFF) << 3;
> - *result = (val * 1000) >> 7;
> + *result = sign_extend32(val, 12) * 1000 / 16;
> break;
> case LTC2990_V1_MSB:
> case LTC2990_V3_MSB:
> /* Vx-Vy, 19.42uV/LSB. Depends on mode. */
> - *result = ltc2990_voltage_to_int(val) * 1942 / (4 * 100);
> + *result = sign_extend32(val, 14) * 1942 / 100;
> break;
> case LTC2990_VCC_MSB:
> /* Vcc, 305.18μV/LSB, 2.5V offset */
> - *result = (ltc2990_voltage_to_int(val) * 30518 /
> - (4 * 100 * 1000)) + 2500;
> + *result = sign_extend32(val, 14) * 30518 / (100 * 1000) + 2500;
> break;
> default:
> return -EINVAL; /* won't happen, keep compiler happy */

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