drivers/pwm/pwm-argon-fan-hat.c

Source file repositories/reference/linux-study-clean/drivers/pwm/pwm-argon-fan-hat.c

File Facts

System
Linux kernel
Corpus path
drivers/pwm/pwm-argon-fan-hat.c
Extension
.c
Size
2774 bytes
Lines
110
Domain
Driver Families
Bucket
drivers/pwm
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

// SPDX-License-Identifier: GPL-2.0
/*
 * Copyright (C) 2025 Marek Vasut
 *
 * Limitations:
 * - no support for offset/polarity
 * - fixed 30 kHz period
 *
 * Argon Fan HAT https://argon40.com/products/argon-fan-hat
 */

#include <linux/err.h>
#include <linux/i2c.h>
#include <linux/module.h>
#include <linux/pwm.h>

#define ARGON40_FAN_HAT_PERIOD_NS	33333	/* ~30 kHz */

#define ARGON40_FAN_HAT_REG_DUTY_CYCLE	0x80

static int argon_fan_hat_round_waveform_tohw(struct pwm_chip *chip,
					     struct pwm_device *pwm,
					     const struct pwm_waveform *wf,
					     void *_wfhw)
{
	u8 *wfhw = _wfhw;

	if (wf->duty_length_ns > ARGON40_FAN_HAT_PERIOD_NS)
		*wfhw = 100;
	else
		*wfhw = mul_u64_u64_div_u64(wf->duty_length_ns, 100, ARGON40_FAN_HAT_PERIOD_NS);

	return 0;
}

static int argon_fan_hat_round_waveform_fromhw(struct pwm_chip *chip,
					       struct pwm_device *pwm,
					       const void *_wfhw,
					       struct pwm_waveform *wf)
{
	const u8 *wfhw = _wfhw;

	wf->period_length_ns = ARGON40_FAN_HAT_PERIOD_NS;
	wf->duty_length_ns = DIV64_U64_ROUND_UP(wf->period_length_ns * *wfhw, 100);
	wf->duty_offset_ns = 0;

	return 0;
}

static int argon_fan_hat_write_waveform(struct pwm_chip *chip,
					struct pwm_device *pwm,
					const void *_wfhw)
{
	struct i2c_client *i2c = pwmchip_get_drvdata(chip);
	const u8 *wfhw = _wfhw;

	return i2c_smbus_write_byte_data(i2c, ARGON40_FAN_HAT_REG_DUTY_CYCLE, *wfhw);
}

static const struct pwm_ops argon_fan_hat_pwm_ops = {
	.sizeof_wfhw = sizeof(u8),
	.round_waveform_fromhw = argon_fan_hat_round_waveform_fromhw,
	.round_waveform_tohw = argon_fan_hat_round_waveform_tohw,
	.write_waveform = argon_fan_hat_write_waveform,
	/*
	 * The controller does not provide any way to read info back,
	 * reading from the controller stops the fan, therefore there
	 * is no .read_waveform here.
	 */
};

static int argon_fan_hat_i2c_probe(struct i2c_client *i2c)
{
	struct pwm_chip *chip = devm_pwmchip_alloc(&i2c->dev, 1, 0);
	int ret;

	if (IS_ERR(chip))
		return PTR_ERR(chip);

	chip->ops = &argon_fan_hat_pwm_ops;
	pwmchip_set_drvdata(chip, i2c);

	ret = devm_pwmchip_add(&i2c->dev, chip);
	if (ret)
		return dev_err_probe(&i2c->dev, ret, "Could not add PWM chip\n");

	return 0;
}

static const struct of_device_id argon_fan_hat_dt_ids[] = {

Annotation

Implementation Notes