auxdisplay: ht16k33: Add LED support

Instantiate a single LED based on the "led" subnode in DT.
This allows the user to control display brightness and blinking (backed
by hardware support) through the LED class API and triggers, and exposes
the display color.  The LED will be named
"auxdisplay:<color>:<function>".

When running in dot-matrix mode and if no "led" subnode is found, the
driver falls back to the traditional backlight mode, to preserve
backwards compatibility.
Signed-off-by: Geert Uytterhoeven <geert@linux-m68k.org>
Reviewed-by: Marek Behún <kabel@kernel.org>
Reviewed-by: Robin van der Gracht <robin@protonic.nl>
Signed-off-by: Miguel Ojeda <ojeda@kernel.org>

drivers/auxdisplay/Kconfig

@@ -176,6 +176,8 @@ config HT16K33
 	select FB_SYS_IMAGEBLIT
 	select INPUT_MATRIXKMAP
 	select FB_BACKLIGHT
+	select NEW_LEDS
+	select LEDS_CLASS
 	select LINEDISP
 	help
 	  Say yes here to add support for Holtek HT16K33, RAM mapping 16*8

drivers/auxdisplay/ht16k33.c

@@ -18,6 +18,7 @@
 #include <linux/backlight.h>
 #include <linux/input.h>
 #include <linux/input/matrix_keypad.h>
+#include <linux/leds.h>
 #include <linux/workqueue.h>
 #include <linux/mm.h>
 
@@ -34,6 +35,10 @@
 
 #define REG_DISPLAY_SETUP		0x80
 #define REG_DISPLAY_SETUP_ON		BIT(0)
+#define REG_DISPLAY_SETUP_BLINK_OFF	(0 << 1)
+#define REG_DISPLAY_SETUP_BLINK_2HZ	(1 << 1)
+#define REG_DISPLAY_SETUP_BLINK_1HZ	(2 << 1)
+#define REG_DISPLAY_SETUP_BLINK_0HZ5	(3 << 1)
 
 #define REG_ROWINT_SET			0xA0
 #define REG_ROWINT_SET_INT_EN		BIT(0)
@@ -94,12 +99,14 @@ struct ht16k33_seg {
 struct ht16k33_priv {
 	struct i2c_client *client;
 	struct delayed_work work;
+	struct led_classdev led;
 	struct ht16k33_keypad keypad;
 	union {
 		struct ht16k33_fbdev fbdev;
 		struct ht16k33_seg seg;
 	};
 	enum display_type type;
+	uint8_t blink;
 };
 
 static const struct fb_fix_screeninfo ht16k33_fb_fix = {
@@ -158,7 +165,7 @@ static DEVICE_ATTR(map_seg14, 0644, map_seg_show, map_seg_store);
 
 static int ht16k33_display_on(struct ht16k33_priv *priv)
 {
-	uint8_t data = REG_DISPLAY_SETUP | REG_DISPLAY_SETUP_ON;
+	uint8_t data = REG_DISPLAY_SETUP | REG_DISPLAY_SETUP_ON | priv->blink;
 
 	return i2c_smbus_write_byte(priv->client, data);
 }
@@ -173,8 +180,10 @@ static int ht16k33_brightness_set(struct ht16k33_priv *priv,
 {
 	int err;
 
-	if (brightness == 0)
+	if (brightness == 0) {
+		priv->blink = REG_DISPLAY_SETUP_BLINK_OFF;
 		return ht16k33_display_off(priv);
+	}
 
 	err = ht16k33_display_on(priv);
 	if (err)
@@ -184,6 +193,49 @@ static int ht16k33_brightness_set(struct ht16k33_priv *priv,
 				    REG_BRIGHTNESS | (brightness - 1));
 }
 
+static int ht16k33_brightness_set_blocking(struct led_classdev *led_cdev,
+					   enum led_brightness brightness)
+{
+	struct ht16k33_priv *priv = container_of(led_cdev, struct ht16k33_priv,
+						 led);
+
+	return ht16k33_brightness_set(priv, brightness);
+}
+
+static int ht16k33_blink_set(struct led_classdev *led_cdev,
+			     unsigned long *delay_on, unsigned long *delay_off)
+{
+	struct ht16k33_priv *priv = container_of(led_cdev, struct ht16k33_priv,
+						 led);
+	unsigned int delay;
+	uint8_t blink;
+	int err;
+
+	if (!*delay_on && !*delay_off) {
+		blink = REG_DISPLAY_SETUP_BLINK_1HZ;
+		delay = 1000;
+	} else if (*delay_on <= 750) {
+		blink = REG_DISPLAY_SETUP_BLINK_2HZ;
+		delay = 500;
+	} else if (*delay_on <= 1500) {
+		blink = REG_DISPLAY_SETUP_BLINK_1HZ;
+		delay = 1000;
+	} else {
+		blink = REG_DISPLAY_SETUP_BLINK_0HZ5;
+		delay = 2000;
+	}
+
+	err = i2c_smbus_write_byte(priv->client,
+				   REG_DISPLAY_SETUP | REG_DISPLAY_SETUP_ON |
+				   blink);
+	if (err)
+		return err;
+
+	priv->blink = blink;
+	*delay_on = *delay_off = delay;
+	return 0;
+}
+
 static void ht16k33_fb_queue(struct ht16k33_priv *priv)
 {
 	struct ht16k33_fbdev *fbdev = &priv->fbdev;
@@ -435,6 +487,35 @@ static void ht16k33_seg14_update(struct work_struct *work)
 	i2c_smbus_write_i2c_block_data(priv->client, 0, ARRAY_SIZE(buf), buf);
 }
 
+static int ht16k33_led_probe(struct device *dev, struct led_classdev *led,
+			     unsigned int brightness)
+{
+	struct led_init_data init_data = {};
+	struct device_node *node;
+	int err;
+
+	/* The LED is optional */
+	node = of_get_child_by_name(dev->of_node, "led");
+	if (!node)
+		return 0;
+
+	init_data.fwnode = of_fwnode_handle(node);
+	init_data.devicename = "auxdisplay";
+	init_data.devname_mandatory = true;
+
+	led->brightness_set_blocking = ht16k33_brightness_set_blocking;
+	led->blink_set = ht16k33_blink_set;
+	led->flags = LED_CORE_SUSPENDRESUME;
+	led->brightness = brightness;
+	led->max_brightness = MAX_BRIGHTNESS;
+
+	err = devm_led_classdev_register_ext(dev, led, &init_data);
+	if (err)
+		dev_err(dev, "Failed to register LED\n");
+
+	return err;
+}
+
 static int ht16k33_keypad_probe(struct i2c_client *client,
 				struct ht16k33_keypad *keypad)
 {
@@ -508,17 +589,24 @@ static int ht16k33_fbdev_probe(struct device *dev, struct ht16k33_priv *priv,
 			       uint32_t brightness)
 {
 	struct ht16k33_fbdev *fbdev = &priv->fbdev;
-	struct backlight_properties bl_props;
-	struct backlight_device *bl;
+	struct backlight_device *bl = NULL;
 	int err;
 
-	/* Backlight */
+	if (priv->led.dev) {
+		err = ht16k33_brightness_set(priv, brightness);
+		if (err)
+			return err;
+	} else {
+		/* backwards compatibility with DT lacking an led subnode */
+		struct backlight_properties bl_props;
+
 		memset(&bl_props, 0, sizeof(struct backlight_properties));
 		bl_props.type = BACKLIGHT_RAW;
 		bl_props.max_brightness = MAX_BRIGHTNESS;
 
-	bl = devm_backlight_device_register(dev, DRIVER_NAME"-bl", dev, priv,
-					    &ht16k33_bl_ops, &bl_props);
+		bl = devm_backlight_device_register(dev, DRIVER_NAME"-bl", dev,
+						    priv, &ht16k33_bl_ops,
+						    &bl_props);
 		if (IS_ERR(bl)) {
 			dev_err(dev, "failed to register backlight\n");
 			return PTR_ERR(bl);
@@ -526,6 +614,7 @@ static int ht16k33_fbdev_probe(struct device *dev, struct ht16k33_priv *priv,
 
 		bl->props.brightness = brightness;
 		ht16k33_bl_update_status(bl);
+	}
 
 	/* Framebuffer (2 bytes per column) */
 	BUILD_BUG_ON(PAGE_SIZE < HT16K33_FB_SIZE);
@@ -663,6 +752,11 @@ static int ht16k33_probe(struct i2c_client *client)
 		dft_brightness = MAX_BRIGHTNESS;
 	}
 
+	/* LED */
+	err = ht16k33_led_probe(dev, &priv->led, dft_brightness);
+	if (err)
+		return err;
+
 	/* Keypad */
 	if (client->irq > 0) {
 		err = ht16k33_keypad_probe(client, &priv->keypad);