drivers/iio/dac/mcp4922.c

Source file repositories/reference/linux-study-clean/drivers/iio/dac/mcp4922.c

File Facts

System
Linux kernel
Corpus path
drivers/iio/dac/mcp4922.c
Extension
.c
Size
4252 bytes
Lines
180
Domain
Driver Families
Bucket
drivers/iio
Inferred role
Driver Families: implementation source
Status
source implementation candidate

Why This File Exists

Repeatable hardware-adapter layer. Deep compatibility for every driver is out of scope; this atlas records patterns, probe lifecycles, bus glue, IRQ/DMA usage, and links back to core abstractions.

Dependency Surface

Detected Declarations

Annotated Snippet

struct mcp4922_state {
	struct spi_device *spi;
	unsigned int value[MCP4922_NUM_CHANNELS];
	unsigned int vref_mv;
	u8 mosi[2] __aligned(IIO_DMA_MINALIGN);
};

#define MCP4922_CHAN(chan, bits) {			\
	.type = IIO_VOLTAGE,				\
	.output = 1,					\
	.indexed = 1,					\
	.channel = chan,				\
	.info_mask_separate = BIT(IIO_CHAN_INFO_RAW),	\
	.info_mask_shared_by_type = BIT(IIO_CHAN_INFO_SCALE),	\
	.scan_type = {					\
		.sign = 'u',				\
		.realbits = (bits),			\
		.storagebits = 16,			\
		.shift = 12 - (bits),			\
	},						\
}

static int mcp4922_spi_write(struct mcp4922_state *state, u8 addr, u32 val)
{
	state->mosi[1] = val & 0xff;
	state->mosi[0] = (addr == 0) ? 0x00 : 0x80;
	state->mosi[0] |= 0x30 | ((val >> 8) & 0x0f);

	return spi_write(state->spi, state->mosi, 2);
}

static int mcp4922_read_raw(struct iio_dev *indio_dev,
		struct iio_chan_spec const *chan,
		int *val,
		int *val2,
		long mask)
{
	struct mcp4922_state *state = iio_priv(indio_dev);

	switch (mask) {
	case IIO_CHAN_INFO_RAW:
		*val = state->value[chan->channel];
		return IIO_VAL_INT;
	case IIO_CHAN_INFO_SCALE:
		*val = state->vref_mv;
		*val2 = chan->scan_type.realbits;
		return IIO_VAL_FRACTIONAL_LOG2;
	default:
		return -EINVAL;
	}
}

static int mcp4922_write_raw(struct iio_dev *indio_dev,
		struct iio_chan_spec const *chan,
		int val,
		int val2,
		long mask)
{
	struct mcp4922_state *state = iio_priv(indio_dev);
	int ret;

	if (val2 != 0)
		return -EINVAL;

	switch (mask) {
	case IIO_CHAN_INFO_RAW:
		if (val < 0 || val > GENMASK(chan->scan_type.realbits - 1, 0))
			return -EINVAL;
		val <<= chan->scan_type.shift;

		ret = mcp4922_spi_write(state, chan->channel, val);
		if (!ret)
			state->value[chan->channel] = val;
		return ret;

	default:
		return -EINVAL;
	}
}

static const struct iio_chan_spec mcp4922_channels[4][MCP4922_NUM_CHANNELS] = {
	[ID_MCP4902] = { MCP4922_CHAN(0, 8),	MCP4922_CHAN(1, 8) },
	[ID_MCP4912] = { MCP4922_CHAN(0, 10),	MCP4922_CHAN(1, 10) },
	[ID_MCP4921] = { MCP4922_CHAN(0, 12),	{} },
	[ID_MCP4922] = { MCP4922_CHAN(0, 12),	MCP4922_CHAN(1, 12) },
};

static const struct iio_info mcp4922_info = {
	.read_raw = &mcp4922_read_raw,
	.write_raw = &mcp4922_write_raw,

Annotation

Implementation Notes