C180_oyster_driver/vbat.c

#include <linux/module.h>
#include <linux/kernel.h>
#include <linux/init.h>
#include <linux/kobject.h>
#include <linux/sysfs.h>
#include <linux/acpi.h>
#include <linux/io.h>
#include <linux/delay.h>
#include "gpioregs.h"

extern struct kobject *hwmon_kobj;

/* Helper functions for IO access */
static uint8_t hwm_read_reg(uint16_t hwm_base, uint8_t reg)
{
    outb(reg, hwm_base + HWM_INDEX_OFFSET);
    return inb(hwm_base + HWM_DATA_OFFSET);
}

static uint8_t hwm_read_reg_retry(uint16_t hwm_base, uint8_t reg)
{
    uint8_t v = hwm_read_reg(hwm_base, reg);
    if (v == 0xFF)
    {
        v = hwm_read_reg(hwm_base, reg);
    }
    return v;
}

static int vin_raw_to_volt(uint8_t raw, int r_top_kohm, int r_bottom_kohm)
{
    int vm = raw * 11;
    if (r_top_kohm > 0 && r_bottom_kohm > 0)
    {
        vm = (vm * (r_top_kohm + r_bottom_kohm)) / r_bottom_kohm;
    }
    return vm;
}

static ssize_t voltage_vbat_show(struct kobject *kobj, struct kobj_attribute *attr,
                                 char *buf)
{
    int vlotage = 0;
    uint8_t raw;
    raw = hwm_read_reg_retry(IT8786_HWM_BASE_DEFAULT, 0x28);

    vlotage = vin_raw_to_volt(raw, 10, 10);

    return sprintf(buf, "%d\n", vlotage);
}

static ssize_t voltage_vbat_store(struct kobject *kobj, struct kobj_attribute *attr,
                                  const char *buf, size_t count)
{
    return -EINVAL;
}

static struct kobj_attribute voltage_vbat =
    __ATTR(voltage_vbat, 0644, voltage_vbat_show, voltage_vbat_store);

static struct attribute *vbat_attrs[] = {
    &voltage_vbat.attr,
    NULL,
};

static struct attribute_group vbat_attr_group = {
    .attrs = vbat_attrs,
};

int vbat_init(void)
{
    int ret = 0;

    ret = sysfs_create_group(hwmon_kobj, &vbat_attr_group);

    return ret;
}

void vbat_exit(void)
{
    sysfs_remove_group(hwmon_kobj, &vbat_attr_group);
}