Re: [PATCH] iio: adc: mcp320x: support more differential voltage measurement

[Jonathan Cameron <jic23@kernel.org>]

On 07/01/16 15:40, Akinobu Mita wrote:
> mcp320x driver supports the pseudo-differential mode by
> in_voltage'IN+'-voltage'IN-'_raw where (IN+, IN-) = (0, 1), (2, 3), ...
> 
> mcp320x chips except MCP3X01 can also select swapped IN+ and IN-
> pairs in the pseudo-differential mode.
> i.e. in_voltage'IN+'-voltage'IN-'_raw where (IN+, IN-) = (1, 0),
> (3, 2), ...
> 
> If the voltage level of IN+ is equal to or less than IN-, the
> resultant code will be 000h.  So it is useful to provide these, too.
> 
> Signed-off-by: Akinobu Mita <akinobu.mita@gmail.com>
> Cc: Oskar Andero <oskar.andero@gmail.com>
> Cc: Jonathan Cameron <jic23@kernel.org>
> Cc: Hartmut Knaack <knaack.h@gmx.de>
> Cc: Lars-Peter Clausen <lars@metafoo.de>
> Cc: Peter Meerwald <pmeerw@pmeerw.net>
> Cc: linux-iio@vger.kernel.org
Looks good to me.   Will let it sit for a while longer on the list
as we have lots of time at this point in a kernel cycle (new one
has just started as far as IIO is concerned)

Jonathan
> ---
>  drivers/iio/adc/mcp320x.c | 31 +++++++++++++++++++------------
>  1 file changed, 19 insertions(+), 12 deletions(-)
> 
> diff --git a/drivers/iio/adc/mcp320x.c b/drivers/iio/adc/mcp320x.c
> index 8569c8e..a9c4acd 100644
> --- a/drivers/iio/adc/mcp320x.c
> +++ b/drivers/iio/adc/mcp320x.c
> @@ -187,26 +187,27 @@ out:
>  		.info_mask_shared_by_type = BIT(IIO_CHAN_INFO_SCALE) \
>  	}
>  
> -#define MCP320X_VOLTAGE_CHANNEL_DIFF(num)			\
> +#define MCP320X_VOLTAGE_CHANNEL_DIFF(chan1, chan2)		\
>  	{							\
>  		.type = IIO_VOLTAGE,				\
>  		.indexed = 1,					\
> -		.channel = (num * 2),				\
> -		.channel2 = (num * 2 + 1),			\
> -		.address = (num * 2),				\
> +		.channel = (chan1),				\
> +		.channel2 = (chan2),				\
> +		.address = (chan1),				\
>  		.differential = 1,				\
>  		.info_mask_separate = BIT(IIO_CHAN_INFO_RAW),	\
>  		.info_mask_shared_by_type = BIT(IIO_CHAN_INFO_SCALE) \
>  	}
>  
>  static const struct iio_chan_spec mcp3201_channels[] = {
> -	MCP320X_VOLTAGE_CHANNEL_DIFF(0),
> +	MCP320X_VOLTAGE_CHANNEL_DIFF(0, 1),
>  };
>  
>  static const struct iio_chan_spec mcp3202_channels[] = {
>  	MCP320X_VOLTAGE_CHANNEL(0),
>  	MCP320X_VOLTAGE_CHANNEL(1),
> -	MCP320X_VOLTAGE_CHANNEL_DIFF(0),
> +	MCP320X_VOLTAGE_CHANNEL_DIFF(0, 1),
> +	MCP320X_VOLTAGE_CHANNEL_DIFF(1, 0),
>  };
>  
>  static const struct iio_chan_spec mcp3204_channels[] = {
> @@ -214,8 +215,10 @@ static const struct iio_chan_spec mcp3204_channels[] = {
>  	MCP320X_VOLTAGE_CHANNEL(1),
>  	MCP320X_VOLTAGE_CHANNEL(2),
>  	MCP320X_VOLTAGE_CHANNEL(3),
> -	MCP320X_VOLTAGE_CHANNEL_DIFF(0),
> -	MCP320X_VOLTAGE_CHANNEL_DIFF(1),
> +	MCP320X_VOLTAGE_CHANNEL_DIFF(0, 1),
> +	MCP320X_VOLTAGE_CHANNEL_DIFF(1, 0),
> +	MCP320X_VOLTAGE_CHANNEL_DIFF(2, 3),
> +	MCP320X_VOLTAGE_CHANNEL_DIFF(3, 2),
>  };
>  
>  static const struct iio_chan_spec mcp3208_channels[] = {
> @@ -227,10 +230,14 @@ static const struct iio_chan_spec mcp3208_channels[] = {
>  	MCP320X_VOLTAGE_CHANNEL(5),
>  	MCP320X_VOLTAGE_CHANNEL(6),
>  	MCP320X_VOLTAGE_CHANNEL(7),
> -	MCP320X_VOLTAGE_CHANNEL_DIFF(0),
> -	MCP320X_VOLTAGE_CHANNEL_DIFF(1),
> -	MCP320X_VOLTAGE_CHANNEL_DIFF(2),
> -	MCP320X_VOLTAGE_CHANNEL_DIFF(3),
> +	MCP320X_VOLTAGE_CHANNEL_DIFF(0, 1),
> +	MCP320X_VOLTAGE_CHANNEL_DIFF(1, 0),
> +	MCP320X_VOLTAGE_CHANNEL_DIFF(2, 3),
> +	MCP320X_VOLTAGE_CHANNEL_DIFF(3, 2),
> +	MCP320X_VOLTAGE_CHANNEL_DIFF(4, 5),
> +	MCP320X_VOLTAGE_CHANNEL_DIFF(5, 4),
> +	MCP320X_VOLTAGE_CHANNEL_DIFF(6, 7),
> +	MCP320X_VOLTAGE_CHANNEL_DIFF(7, 6),
>  };
>  
>  static const struct iio_info mcp320x_info = {
>