mfd: cros_ec: Add cros-usbpd-notify subdevice

Add the cros-usbpd-notify driver as a subdevice on platforms that
support the EC_FEATURE_USB_PD EC feature flag and don't have the
ACPI PD notification device defined.

This driver allows other cros-ec devices to receive PD event
notifications from the Chrome OS Embedded Controller (EC) via a
notification chain.
Signed-off-by: Prashant Malani <pmalani@chromium.org>
Reviewed-by: Benson Leung <bleung@chromium.org>
Signed-off-by: Lee Jones <lee.jones@linaro.org>

drivers/mfd/cros_ec_dev.c

@@ -5,6 +5,7 @@
  * Copyright (C) 2014 Google, Inc.
  */
 
+#include <linux/kconfig.h>
 #include <linux/mfd/core.h>
 #include <linux/mfd/cros_ec.h>
 #include <linux/module.h>
@@ -87,6 +88,10 @@ static const struct mfd_cell cros_usbpd_charger_cells[] = {
 	{ .name = "cros-usbpd-logger", },
 };
 
+static const struct mfd_cell cros_usbpd_notify_cells[] = {
+	{ .name = "cros-usbpd-notify", },
+};
+
 static const struct cros_feature_to_cells cros_subdevices[] = {
 	{
 		.id		= EC_FEATURE_CEC,
@@ -202,6 +207,23 @@ static int ec_device_probe(struct platform_device *pdev)
 		}
 	}
 
+	/*
+	 * The PD notifier driver cell is separate since it only needs to be
+	 * explicitly added on platforms that don't have the PD notifier ACPI
+	 * device entry defined.
+	 */
+	if (IS_ENABLED(CONFIG_OF)) {
+		if (cros_ec_check_features(ec, EC_FEATURE_USB_PD)) {
+			retval = mfd_add_hotplug_devices(ec->dev,
+					cros_usbpd_notify_cells,
+					ARRAY_SIZE(cros_usbpd_notify_cells));
+			if (retval)
+				dev_err(ec->dev,
+					"failed to add PD notify devices: %d\n",
+					retval);
+		}
+	}
+
 	/*
 	 * The following subdevices cannot be detected by sending the
 	 * EC_FEATURE_GET_CMD to the Embedded Controller device.