drivers/hwmon/mcp3021.c

Source file repositories/reference/linux-study-clean/drivers/hwmon/mcp3021.c

File Facts

System
Linux kernel
Corpus path
drivers/hwmon/mcp3021.c
Extension
.c
Size
4984 bytes
Lines
209
Domain
Driver Families
Bucket
drivers/hwmon
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 mcp3021_data {
	struct i2c_client *client;
	u32 vdd;        /* supply and reference voltage in millivolt */
	u16 sar_shift;
	u16 sar_mask;
	u8 output_res;
};

static inline u16 volts_from_reg(struct mcp3021_data *data, u16 val)
{
	return DIV_ROUND_CLOSEST(data->vdd * val, 1 << data->output_res);
}

static int mcp3021_read(struct device *dev, enum hwmon_sensor_types type,
			u32 attr, int channel, long *val)
{
	struct mcp3021_data *data = dev_get_drvdata(dev);
	struct i2c_client *client = data->client;
	__be16 buf;
	u16 reg;
	int ret;

	if (type != hwmon_in)
		return -EOPNOTSUPP;

	ret = i2c_master_recv(client, (char *)&buf, 2);
	if (ret < 0)
		return ret;
	if (ret != 2)
		return -EIO;

	/* The output code of the MCP3021 is transmitted with MSB first. */
	reg = be16_to_cpu(buf);

	/*
	 * The ten-bit output code is composed of the lower 4-bit of the
	 * first byte and the upper 6-bit of the second byte.
	 */
	reg = (reg >> data->sar_shift) & data->sar_mask;

	*val = volts_from_reg(data, reg);

	return 0;
}

static umode_t mcp3021_is_visible(const void *_data,
				  enum hwmon_sensor_types type,
				  u32 attr, int channel)
{
	if (type != hwmon_in)
		return 0;

	if (attr != hwmon_in_input)
		return 0;

	return 0444;
}

static const struct hwmon_channel_info * const mcp3021_info[] = {
	HWMON_CHANNEL_INFO(in, HWMON_I_INPUT),
	NULL
};

static const struct hwmon_ops mcp3021_hwmon_ops = {
	.is_visible = mcp3021_is_visible,
	.read = mcp3021_read,
};

static const struct hwmon_chip_info mcp3021_chip_info = {
	.ops = &mcp3021_hwmon_ops,
	.info = mcp3021_info,
};

static int mcp3021_probe(struct i2c_client *client)
{
	struct mcp3021_data *data = NULL;
	struct device_node *np = client->dev.of_node;
	struct device *hwmon_dev;
	enum chips type;

	if (!i2c_check_functionality(client->adapter, I2C_FUNC_I2C))
		return -ENODEV;

	data = devm_kzalloc(&client->dev, sizeof(struct mcp3021_data),
			    GFP_KERNEL);
	if (!data)
		return -ENOMEM;

	i2c_set_clientdata(client, data);

Annotation

Implementation Notes