Re: [PATCH v5] iio: temperature: add support for Maxim thermocouple chips

[Marek Vasut <marex@denx.de>]

On 07/01/2016 04:52 AM, Matt Ranostay wrote:
> Add initial driver support for MAX6675, and MAX31855 thermocouple chips.
> 
> Cc: Marek Vasut <marex@denx.de>
> Cc: Matt Porter <mporter@konsulko.com>
> Signed-off-by: Matt Ranostay <mranostay@gmail.com>
> ---
> 
> Changes from v1:
> * switch to iio_device_*_direct_mode wrappers
> * add const to structs
> * removed useless cast
> 
> Changes from v2:
> * mark buffer data invalid on disconnected thermocouple
> * add .address = 0 to be consistent
> * add missing scan_mask for the max31855 part
> 
> Changes from v3:
> * fixed several typos of max31855 part number
> 
> Changes from v4:
> * drop maxim_thermocouple_validate_buffer() due to peer review saying
>   this is an incorrect way to signal an invalid reading

[...]

> +const struct iio_chan_spec max31855_channels[] = {
> +	{	/* thermocouple temperature */
> +		.type = IIO_TEMP,
> +		.address = 2,
> +		.info_mask_separate =
> +			BIT(IIO_CHAN_INFO_RAW) | BIT(IIO_CHAN_INFO_SCALE),
> +		.scan_index = 0,
> +		.scan_type = {
> +			.sign = 's',
> +			.realbits = 14,
> +			.storagebits = 16,
> +			.shift = 2,
> +			.endianness = IIO_BE,
> +		},
> +	},
> +	{	/* cold junction temperature */
> +		.type = IIO_TEMP,
> +		.address = 0,
> +		.channel2 = IIO_MOD_TEMP_AMBIENT,
> +		.modified = 1,
> +		.info_mask_separate =
> +			BIT(IIO_CHAN_INFO_RAW) | BIT(IIO_CHAN_INFO_SCALE),
> +		.scan_index = 1,
> +		.scan_type = {
> +			.sign = 's',
> +			.realbits = 12,
> +			.storagebits = 16,
> +			.shift = 4,
> +			.endianness = IIO_BE,
> +		},
> +	},
> +	IIO_CHAN_SOFT_TIMESTAMP(2),
> +};
> +
> +static const unsigned long max31855_scan_masks[] = {0x3, 0};
> +
> +struct maxim_thermocouple_chip {
> +	const struct iio_chan_spec *channels;
> +	const unsigned long *scan_masks;
> +	int num_channels;

const u8 or u32 ?

> +	int read_size;

const u8

> +	/* bit-check for valid input */
> +	int status_bit;

const bool ?

You can save some slop in here, see also:
http://www.catb.org/esr/structure-packing/

> +};
> +
> +const struct maxim_thermocouple_chip maxim_thermocouple_chips[] = {
> +	[MAX6675] = {
> +			.channels = max6675_channels,
> +			.num_channels = ARRAY_SIZE(max6675_channels),
> +			.read_size = 2,
> +			.status_bit = BIT(2),
> +		},
> +	[MAX31855] = {
> +			.channels = max31855_channels,
> +			.num_channels = ARRAY_SIZE(max31855_channels),
> +			.read_size = 4,
> +			.scan_masks = max31855_scan_masks,
> +			.status_bit = BIT(16),
> +		},
> +};
[...]

-- 
Best regards,
Marek Vasut