dm: backlight: Add a backlight uclass

LCD panels normally have a backlight which can be controlled to illuminate
the LCD contents. Add a uclass to support this. Initially it only has a
method to enable the backlight.

Signed-off-by: Simon Glass <sjg@chromium.org>

drivers/video/Makefile

@@ -7,6 +7,7 @@
 
 ifdef CONFIG_DM
 obj-$(CONFIG_DISPLAY_PORT) += dp-uclass.o
+obj-$(CONFIG_DM_VIDEO) += backlight-uclass.o
 obj-$(CONFIG_DM_VIDEO) += video-uclass.o vidconsole-uclass.o console_normal.o
 obj-$(CONFIG_DM_VIDEO) += video_bmp.o
 obj-$(CONFIG_VIDEO_ROTATION) += console_rotate.o

drivers/video/backlight-uclass.c

+/*
+ * Copyright (c) 2016 Google, Inc
+ * Written by Simon Glass <sjg@chromium.org>
+ *
+ * SPDX-License-Identifier:	GPL-2.0+
+ */
+
+#include <common.h>
+#include <dm.h>
+#include <backlight.h>
+
+int backlight_enable(struct udevice *dev)
+{
+	const struct backlight_ops *ops = backlight_get_ops(dev);
+
+	if (!ops->enable)
+		return -ENOSYS;
+
+	return ops->enable(dev);
+}
+
+UCLASS_DRIVER(backlight) = {
+	.id		= UCLASS_PANEL_BACKLIGHT,
+	.name		= "backlight",
+};

include/backlight.h

+/*
+ * Copyright (c) 2016 Google, Inc
+ * Written by Simon Glass <sjg@chromium.org>
+ *
+ * SPDX-License-Identifier:	GPL-2.0+
+ */
+
+#ifndef _BACKLIGHT_H
+#define _BACKLIGHT_H
+
+struct backlight_ops {
+	/**
+	 * enable() - Enable a backlight
+	 *
+	 * @dev:	Backlight device to enable
+	 * @return 0 if OK, -ve on error
+	 */
+	int (*enable)(struct udevice *dev);
+};
+
+#define backlight_get_ops(dev)	((struct backlight_ops *)(dev)->driver->ops)
+
+/**
+ * backlight_enable() - Enable a backlight
+ *
+ * @dev:	Backlight device to enable
+ * @return 0 if OK, -ve on error
+ */
+int backlight_enable(struct udevice *dev);
+
+#endif

include/dm/uclass-id.h

@@ -45,6 +45,7 @@ enum uclass_id {
 	UCLASS_MMC,		/* SD / MMC card or chip */
 	UCLASS_MOD_EXP,		/* RSA Mod Exp device */
 	UCLASS_MTD,		/* Memory Technology Device (MTD) device */
+	UCLASS_PANEL_BACKLIGHT,	/* Backlight controller for panel */
 	UCLASS_PCH,		/* x86 platform controller hub */
 	UCLASS_PCI,		/* PCI bus */
 	UCLASS_PCI_GENERIC,	/* Generic PCI bus device */