On Wed, Nov 16, 2016 at 04:23:53PM -0600, Matt Weber wrote:
> From: Jared Bents <jared.bents@xxxxxxxxxxxxxxxxxxx>
>
> Converts the unsigned temperature values from the i2c read
> to be sign extended as defined in the datasheet so that
> negative temperatures are properly read.
>
> Signed-off-by: Jared Bents <jared.bents@xxxxxxxxxxxxxxxxxxx>
> Signed-off-by: Matt Weber <matthew.weber@xxxxxxxxxxxxxxxxxxx>
> ---
> drivers/hwmon/amc6821.c | 2 +-
> 1 file changed, 1 insertion(+), 1 deletion(-)
>
> diff --git a/drivers/hwmon/amc6821.c b/drivers/hwmon/amc6821.c
> index 12e851a..d7368f7 100644
> --- a/drivers/hwmon/amc6821.c
> +++ b/drivers/hwmon/amc6821.c
> @@ -188,7 +188,7 @@ static struct amc6821_data *amc6821_update_device(struct device *dev)
> !data->valid) {
>
> for (i = 0; i < TEMP_IDX_LEN; i++)
> - data->temp[i] = i2c_smbus_read_byte_data(client,
> + data->temp[i] = (int8_t) i2c_smbus_read_byte_data(client,
How does that fix anything ? The only difference is that errors reported from
i2c_smbus_read_byte_data() are now capped off and stored as 0xff and no longer
as negative numbers. I don't see how a value of 0xff read from the chip would
now be reported as -1 degrees C; it should be reported as 255 degrees C as it
was all along. What am I missing here ?
A real fix would be to actually check for errors either here or in the show
function (temp[] < 0 indicates a transfer error), and to use sign_extend()
to convert the 8-bit reading to a signed value.
Guenter
> temp_reg[i]);
>
> data->stat1 = i2c_smbus_read_byte_data(client,
> --
> 1.9.1
>
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