mfd: cros_ec_dev: Load lightbar module only present

The pixel lightbar is only present on chromebook pixel (link), pixel 2
and pixel C. For the latter two, the EC reports its presence.
Instead of always loading the lightbar driver on all chromebook, only
load it when reported by the EC or Link device.
Signed-off-by: Gwendal Grignou <gwendal@chromium.org>
Acked-by: Enric Balletbo i Serra <enric.balletbo@collabora.com>
Tested-by: Stephen Boyd <swboyd@chromium.org>
Reviewed-by: Stephen Boyd <swboyd@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/dmi.h>
 #include <linux/kconfig.h>
 #include <linux/mfd/core.h>
 #include <linux/module.h>
@@ -112,10 +113,13 @@ static const struct cros_feature_to_cells cros_subdevices[] = {
 static const struct mfd_cell cros_ec_platform_cells[] = {
 	{ .name = "cros-ec-chardev", },
 	{ .name = "cros-ec-debugfs", },
-	{ .name = "cros-ec-lightbar", },
 	{ .name = "cros-ec-sysfs", },
 };
 
+static const struct mfd_cell cros_ec_lightbar_cells[] = {
+	{ .name = "cros-ec-lightbar", }
+};
+
 static const struct mfd_cell cros_ec_vbc_cells[] = {
 	{ .name = "cros-ec-vbc", }
 };
@@ -206,6 +210,20 @@ static int ec_device_probe(struct platform_device *pdev)
 		}
 	}
 
+	/*
+	 * Lightbar is a special case. Newer devices support autodetection,
+	 * but older ones do not.
+	 */
+	if (cros_ec_check_features(ec, EC_FEATURE_LIGHTBAR) ||
+	    dmi_match(DMI_PRODUCT_NAME, "Link")) {
+		retval = mfd_add_hotplug_devices(ec->dev,
+					cros_ec_lightbar_cells,
+					ARRAY_SIZE(cros_ec_lightbar_cells));
+		if (retval)
+			dev_warn(ec->dev, "failed to add lightbar: %d\n",
+				 retval);
+	}
+
 	/*
 	 * 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