WhyCan Forum(哇酷开发者社区)

static int sunxi_pctrl_parse_drive_prop(struct device_node *node)
{
	u32 val;

	/* Try the new style binding */
	if (!of_property_read_u32(node, "drive-strength", &val)) {
		/* We can't go below 10mA ... */
		if (val < 10)
			return -EINVAL;

		/* ... and only up to 40 mA ... */
		if (val > 40)
			val = 40;

		/* by steps of 10 mA */
		return rounddown(val, 10);
	}

	/* And then fall back to the old binding */
	if (of_property_read_u32(node, "allwinner,drive", &val))
		return -EINVAL;

	return (val + 1) * 10;
}