drivers/hwmon/ltc4245.c

Source file repositories/reference/linux-study-clean/drivers/hwmon/ltc4245.c

File Facts

System
Linux kernel
Corpus path
drivers/hwmon/ltc4245.c
Extension
.c
Size
11911 bytes
Lines
483
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 ltc4245_data {
	struct i2c_client *client;

	bool valid;
	unsigned long last_updated; /* in jiffies */

	/* Control registers */
	u8 cregs[0x08];

	/* Voltage registers */
	u8 vregs[0x0d];

	/* GPIO ADC registers */
	bool use_extra_gpios;
	int gpios[3];
};

/*
 * Update the readings from the GPIO pins. If the driver has been configured to
 * sample all GPIO's as analog voltages, a round-robin sampling method is used.
 * Otherwise, only the configured GPIO pin is sampled.
 *
 * LOCKING: must hold data->update_lock
 */
static void ltc4245_update_gpios(struct device *dev)
{
	struct ltc4245_data *data = dev_get_drvdata(dev);
	struct i2c_client *client = data->client;
	u8 gpio_curr, gpio_next, gpio_reg;
	int i;

	/* no extra gpio support, we're basically done */
	if (!data->use_extra_gpios) {
		data->gpios[0] = data->vregs[LTC4245_GPIOADC - 0x10];
		return;
	}

	/*
	 * If the last reading was too long ago, then we mark all old GPIO
	 * readings as stale by setting them to -EAGAIN
	 */
	if (time_after(jiffies, data->last_updated + 5 * HZ)) {
		for (i = 0; i < ARRAY_SIZE(data->gpios); i++)
			data->gpios[i] = -EAGAIN;
	}

	/*
	 * Get the current GPIO pin
	 *
	 * The datasheet calls these GPIO[1-3], but we'll calculate the zero
	 * based array index instead, and call them GPIO[0-2]. This is much
	 * easier to think about.
	 */
	gpio_curr = (data->cregs[LTC4245_GPIO] & 0xc0) >> 6;
	if (gpio_curr > 0)
		gpio_curr -= 1;

	/* Read the GPIO voltage from the GPIOADC register */
	data->gpios[gpio_curr] = data->vregs[LTC4245_GPIOADC - 0x10];

	/* Find the next GPIO pin to read */
	gpio_next = (gpio_curr + 1) % ARRAY_SIZE(data->gpios);

	/*
	 * Calculate the correct setting for the GPIO register so it will
	 * sample the next GPIO pin
	 */
	gpio_reg = (data->cregs[LTC4245_GPIO] & 0x3f) | ((gpio_next + 1) << 6);

	/* Update the GPIO register */
	i2c_smbus_write_byte_data(client, LTC4245_GPIO, gpio_reg);

	/* Update saved data */
	data->cregs[LTC4245_GPIO] = gpio_reg;
}

static struct ltc4245_data *ltc4245_update_device(struct device *dev)
{
	struct ltc4245_data *data = dev_get_drvdata(dev);
	struct i2c_client *client = data->client;
	s32 val;
	int i;

	if (time_after(jiffies, data->last_updated + HZ) || !data->valid) {
		/* Read control registers -- 0x00 to 0x07 */
		for (i = 0; i < ARRAY_SIZE(data->cregs); i++) {
			val = i2c_smbus_read_byte_data(client, i);
			if (unlikely(val < 0))
				data->cregs[i] = 0;
			else

Annotation

Implementation Notes