BQ27220: BQ27220

I'm porting bq27220 driver (bq27xxx_battery.c)
https://git.ti.com/cgit/ti-linux-kernel/ti-linux-kernel/tree/drivers/power/supply/bq27xxx_battery.c?h=ti-linux-4.9.y

But I cannot found about NAC( Nominal Available Capacity) definition in BQ27220 specs.

Some sample code as below:

BQ27XXX_REG_NAC,	/* Nominal Available Capacity */

/*
 * Return the battery Nominal available capacity in µAh
 * Or < 0 if something fails.
 */
static inline int bq27xxx_battery_read_nac(struct bq27xxx_device_info *di)
{
	int flags;

	if (di->chip == BQ27000 || di->chip == BQ27010) {
		flags = bq27xxx_read(di, BQ27XXX_REG_FLAGS, true);
		if (flags >= 0 && (flags & BQ27000_FLAG_CI))
			return -ENODATA;
	}

	return bq27xxx_battery_read_charge(di, BQ27XXX_REG_NAC);
}

case POWER_SUPPLY_PROP_CHARGE_NOW:
	ret = bq27xxx_simple_value(bq27xxx_battery_read_nac(di), val);