On Tue, 22 Aug 2017 15:33:00 +0200
Lukas Wunner <lukas@xxxxxxxxx> wrote:
> Commit f686a36b4b79 ("iio: adc: mcp320x: Add support for mcp3301")
> returns a signed voltage from mcp320x_adc_conversion() but neglects that
> the caller interprets a negative return value as failure. Only mcp3301
> (and the upcoming mcp3550/1/3) is affected as the other chips are
> incapable of measuring negative voltages.
>
> Fix and while at it, add mcp3301 to the list of supported chips at the
> top of the file.
>
> Fixes: f686a36b4b79 ("iio: adc: mcp320x: Add support for mcp3301")
> Cc: Andrea Galbusera <gizero@xxxxxxxxx>
> Signed-off-by: Lukas Wunner <lukas@xxxxxxxxx>
Applied to the fixes-togreg branch of iio.git and marked for stable.
Thanks,
Jonathan
> ---
> drivers/iio/adc/mcp320x.c | 24 +++++++++++++++---------
> 1 file changed, 15 insertions(+), 9 deletions(-)
>
> diff --git a/drivers/iio/adc/mcp320x.c b/drivers/iio/adc/mcp320x.c
> index 45d043c9a888..071dd23a33d9 100644
> --- a/drivers/iio/adc/mcp320x.c
> +++ b/drivers/iio/adc/mcp320x.c
> @@ -17,6 +17,8 @@
> * MCP3204
> * MCP3208
> * ------------
> + * 13 bit converter
> + * MCP3301
> *
> * Datasheet can be found here:
> * http://ww1.microchip.com/downloads/en/DeviceDoc/21293C.pdf mcp3001
> @@ -96,7 +98,7 @@ static int mcp320x_channel_to_tx_data(int device_index,
> }
>
> static int mcp320x_adc_conversion(struct mcp320x *adc, u8 channel,
> - bool differential, int device_index)
> + bool differential, int device_index, int *val)
> {
> int ret;
>
> @@ -117,19 +119,25 @@ static int mcp320x_adc_conversion(struct mcp320x *adc, u8 channel,
>
> switch (device_index) {
> case mcp3001:
> - return (adc->rx_buf[0] << 5 | adc->rx_buf[1] >> 3);
> + *val = (adc->rx_buf[0] << 5 | adc->rx_buf[1] >> 3);
> + return 0;
> case mcp3002:
> case mcp3004:
> case mcp3008:
> - return (adc->rx_buf[0] << 2 | adc->rx_buf[1] >> 6);
> + *val = (adc->rx_buf[0] << 2 | adc->rx_buf[1] >> 6);
> + return 0;
> case mcp3201:
> - return (adc->rx_buf[0] << 7 | adc->rx_buf[1] >> 1);
> + *val = (adc->rx_buf[0] << 7 | adc->rx_buf[1] >> 1);
> + return 0;
> case mcp3202:
> case mcp3204:
> case mcp3208:
> - return (adc->rx_buf[0] << 4 | adc->rx_buf[1] >> 4);
> + *val = (adc->rx_buf[0] << 4 | adc->rx_buf[1] >> 4);
> + return 0;
> case mcp3301:
> - return sign_extend32((adc->rx_buf[0] & 0x1f) << 8 | adc->rx_buf[1], 12);
> + *val = sign_extend32((adc->rx_buf[0] & 0x1f) << 8
> + | adc->rx_buf[1], 12);
> + return 0;
> default:
> return -EINVAL;
> }
> @@ -150,12 +158,10 @@ static int mcp320x_read_raw(struct iio_dev *indio_dev,
> switch (mask) {
> case IIO_CHAN_INFO_RAW:
> ret = mcp320x_adc_conversion(adc, channel->address,
> - channel->differential, device_index);
> -
> + channel->differential, device_index, val);
> if (ret < 0)
> goto out;
>
> - *val = ret;
> ret = IIO_VAL_INT;
> break;
>
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