mfd: Conditionally add WM831x backlight subdevice

The WM831x backlight driver requires at least the specification of the
current sink to use and a maximum current to allow them to function and
will actively interfere with other users of the regulators it uses if
misconfigured so only register the subdevice for it if this platform
data has been supplied.

Signed-off-by: Mark Brown <[e-mail]>
Signed-off-by: Samuel Ortiz <[e-mail]>

drivers/mfd/wm831x-core.c

···
 	},
 };
 
+static struct mfd_cell backlight_devs[] = {
+	{
+		.name = "wm831x-backlight",
+	},
+};
+
 /*
  * Instantiate the generic non-control parts of the device.
  */
···
 	if (ret != 0) {
 		dev_err(wm831x->dev, "Failed to add children\n");
 		goto err_irq;
+	}
+
+	if (pdata && pdata->backlight) {
+		/* Treat errors as non-critical */
+		ret = mfd_add_devices(wm831x->dev, -1, backlight_devs,
+				      ARRAY_SIZE(backlight_devs), NULL, 0);
+		if (ret < 0)
+			dev_err(wm831x->dev, "Failed to add backlight: %d\n",
+				ret);
 	}
 
 	if (pdata && pdata->post_init) {

include/linux/mfd/wm831x/pdata.h

···
 struct wm831x;
 struct regulator_init_data;
 
+struct wm831x_backlight_pdata {
+	int isink;     /** ISINK to use, 1 or 2 */
+	int max_uA;    /** Maximum current to allow */
+};
+
 struct wm831x_backup_pdata {
 	int charger_enable;
 	int no_constant_voltage;  /** Disable constant voltage charging */
···
 	int (*post_init)(struct wm831x *wm831x);
 
 	int gpio_base;
+	struct wm831x_backlight_pdata *backlight;
 	struct wm831x_backup_pdata *backup;
 	struct wm831x_battery_pdata *battery;
 	struct wm831x_touch_pdata *touch;