Merge tag 'auxdisplay-for-linus-v5.16' of git://github.com/ojeda/linux

Pull auxdisplay updates from Miguel Ojeda:

- 4-digit 7-segment and quad alphanumeric display support for the
ht16k33 driver, allowing the user to display and scroll text
messages, from Geert Uytterhoeven.

- An assortment of fixes and cleanups from Geert Uytterhoeven.

- Header cleanups from Mianhan Liu.

- Whitespace cleanup from Huiquan Deng.

* tag 'auxdisplay-for-linus-v5.16' of git://github.com/ojeda/linux: (26 commits)
MAINTAINERS: Add DT Bindings for Auxiliary Display Drivers
auxdisplay: cfag12864bfb: code indent should use tabs where possible
auxdisplay: ht16k33: remove superfluous header files
auxdisplay: ks0108: remove superfluous header files
auxdisplay: cfag12864bfb: remove superfluous header files
auxdisplay: ht16k33: Make use of device properties
auxdisplay: ht16k33: Add LED support
dt-bindings: auxdisplay: ht16k33: Document LED subnode
auxdisplay: ht16k33: Add support for segment displays
auxdisplay: ht16k33: Extract frame buffer probing
auxdisplay: ht16k33: Extract ht16k33_brightness_set()
auxdisplay: ht16k33: Move delayed work
auxdisplay: ht16k33: Add helper variable dev
auxdisplay: ht16k33: Convert to simple i2c probe function
auxdisplay: ht16k33: Remove unneeded error check in keypad probe()
auxdisplay: ht16k33: Use HT16K33_FB_SIZE in ht16k33_initialize()
auxdisplay: ht16k33: Fix frame buffer device blanking
auxdisplay: ht16k33: Connect backlight to fbdev
auxdisplay: linedisp: Add support for changing scroll rate
auxdisplay: linedisp: Use kmemdup_nul() helper
...

Documentation/devicetree/bindings/auxdisplay/holtek,ht16k33.yaml

···
 
 properties:
   compatible:
-    const: holtek,ht16k33
+    oneOf:
+      - items:
+          - enum:
+              - adafruit,3108  # 0.56" 4-Digit 7-Segment FeatherWing Display (Red)
+              - adafruit,3130  # 0.54" Quad Alphanumeric FeatherWing Display (Red)
+          - const: holtek,ht16k33
+
+      - const: holtek,ht16k33     # Generic 16*8 LED controller with dot-matrix display
 
   reg:
     maxItems: 1
 
   refresh-rate-hz:
     maxItems: 1
-    description: Display update interval in Hertz
+    description: Display update interval in Hertz for dot-matrix displays
 
   interrupts:
     maxItems: 1
···
     default: 16
     description: Initial brightness level
 
+  led:
+    type: object
+    $ref: /schemas/leds/common.yaml#
+    unevaluatedProperties: false
+
 required:
   - compatible
   - reg
-  - refresh-rate-hz
+
+if:
+  properties:
+    compatible:
+      const: holtek,ht16k33
+then:
+  required:
+    - refresh-rate-hz
 
 additionalProperties: false
 
···
   - |
     #include <dt-bindings/interrupt-controller/irq.h>
     #include <dt-bindings/input/input.h>
+    #include <dt-bindings/leds/common.h>
     i2c1 {
             #address-cells = <1>;
             #size-cells = <0>;
···
                                    <MATRIX_KEY(4, 1, KEY_F9)>,
                                    <MATRIX_KEY(5, 1, KEY_F3)>,
                                    <MATRIX_KEY(6, 1, KEY_F1)>;
+
+                    led {
+                            color = <LED_COLOR_ID_RED>;
+                            function = LED_FUNCTION_BACKLIGHT;
+                            linux,default-trigger = "backlight";
+                    };
             };
       };

MAINTAINERS

···
 AUXILIARY DISPLAY DRIVERS
 M:	Miguel Ojeda <[e-mail]>
 S:	Maintained
+F:	Documentation/devicetree/bindings/auxdisplay/
 F:	drivers/auxdisplay/
 F:	include/linux/cfag12864b.h
 

drivers/auxdisplay/Kconfig

···
 	  This is some character LCD core interface that multiple drivers can
 	  use.
 
+config LINEDISP
+	tristate "Character line display core support" if COMPILE_TEST
+	help
+	  This is the core support for single-line character displays, to be
+	  selected by drivers that use it.
+
 config HD44780_COMMON
 	tristate "Common functions for HD44780 (and compatibles) LCD displays" if COMPILE_TEST
 	select CHARLCD
···
 	depends on HAS_IOMEM
 	default y if MIPS_MALTA
 	select MFD_SYSCON
+	select LINEDISP
 	help
 	  Enable this to support the simple ASCII LCD displays found on
 	  development boards such as the MIPS Boston, MIPS Malta & MIPS SEAD3
···
 
 config HT16K33
 	tristate "Holtek Ht16K33 LED controller with keyscan"
-	depends on FB && OF && I2C && INPUT
+	depends on FB && I2C && INPUT
 	select FB_SYS_FOPS
 	select FB_SYS_FILLRECT
 	select FB_SYS_COPYAREA
 	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
 	  LED controller driver with keyscan.

drivers/auxdisplay/Makefile

···
 obj-$(CONFIG_HT16K33)		+= ht16k33.o
 obj-$(CONFIG_PARPORT_PANEL)	+= panel.o
 obj-$(CONFIG_LCD2S)		+= lcd2s.o
+obj-$(CONFIG_LINEDISP)		+= line-display.o

drivers/auxdisplay/cfag12864bfb.c

···
 #include <linux/init.h>
 #include <linux/module.h>
 #include <linux/kernel.h>
-#include <linux/delay.h>
 #include <linux/errno.h>
 #include <linux/fb.h>
 #include <linux/mm.h>
 #include <linux/platform_device.h>
-#include <linux/string.h>
-#include <linux/uaccess.h>
 #include <linux/cfag12864b.h>
 
 #define CFAG12864BFB_NAME "cfag12864bfb"
···
 	.yres_virtual = CFAG12864B_HEIGHT,
 	.bits_per_pixel = 1,
 	.red = { 0, 1, 0 },
-      	.green = { 0, 1, 0 },
-      	.blue = { 0, 1, 0 },
+	.green = { 0, 1, 0 },
+	.blue = { 0, 1, 0 },
 	.left_margin = 0,
 	.right_margin = 0,
 	.upper_margin = 0,
···
 static int cfag12864bfb_probe(struct platform_device *device)
 {
 	int ret = -EINVAL;
- 	struct fb_info *info = framebuffer_alloc(0, &device->dev);
+	struct fb_info *info = framebuffer_alloc(0, &device->dev);
 
 	if (!info)
 		goto none;

drivers/auxdisplay/ht16k33.c

···
  * Author: Robin van der Gracht <[e-mail]>
  *
  * Copyright: (C) 2016 Protonic Holland.
+ * Copyright (C) 2021 Glider bv
  */
 
 #include <linux/kernel.h>
 #include <linux/module.h>
 #include <linux/interrupt.h>
 #include <linux/i2c.h>
-#include <linux/of.h>
+#include <linux/property.h>
 #include <linux/fb.h>
-#include <linux/slab.h>
 #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>
+
+#include <linux/map_to_7segment.h>
+#include <linux/map_to_14segment.h>
+
+#include <asm/unaligned.h>
+
+#include "line-display.h"
 
 /* Registers */
 #define REG_SYSTEM_SETUP		0x20
···
 
 #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)
···
 #define BYTES_PER_ROW		(HT16K33_MATRIX_LED_MAX_ROWS / 8)
 #define HT16K33_FB_SIZE		(HT16K33_MATRIX_LED_MAX_COLS * BYTES_PER_ROW)
 
+enum display_type {
+	DISP_MATRIX = 0,
+	DISP_QUAD_7SEG,
+	DISP_QUAD_14SEG,
+};
+
 struct ht16k33_keypad {
 	struct i2c_client *client;
 	struct input_dev *dev;
···
 	uint32_t refresh_rate;
 	uint8_t *buffer;
 	uint8_t *cache;
-	struct delayed_work work;
+};
+
+struct ht16k33_seg {
+	struct linedisp linedisp;
+	union {
+		struct seg7_conversion_map seg7;
+		struct seg14_conversion_map seg14;
+	} map;
+	unsigned int map_size;
+	char curr[4];
 };
 
 struct ht16k33_priv {
 	struct i2c_client *client;
+	struct delayed_work work;
+	struct led_classdev led;
 	struct ht16k33_keypad keypad;
-	struct ht16k33_fbdev fbdev;
+	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 = {
···
 	.vmode = FB_VMODE_NONINTERLACED,
 };
 
+static const SEG7_DEFAULT_MAP(initial_map_seg7);
+static const SEG14_DEFAULT_MAP(initial_map_seg14);
+
+static ssize_t map_seg_show(struct device *dev, struct device_attribute *attr,
+			    char *buf)
+{
+	struct ht16k33_priv *priv = dev_get_drvdata(dev);
+
+	memcpy(buf, &priv->seg.map, priv->seg.map_size);
+	return priv->seg.map_size;
+}
+
+static ssize_t map_seg_store(struct device *dev, struct device_attribute *attr,
+			     const char *buf, size_t cnt)
+{
+	struct ht16k33_priv *priv = dev_get_drvdata(dev);
+
+	if (cnt != priv->seg.map_size)
+		return -EINVAL;
+
+	memcpy(&priv->seg.map, buf, cnt);
+	return cnt;
+}
+
+static DEVICE_ATTR(map_seg7, 0644, map_seg_show, map_seg_store);
+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);
 }
···
 	return i2c_smbus_write_byte(priv->client, REG_DISPLAY_SETUP);
 }
 
+static int ht16k33_brightness_set(struct ht16k33_priv *priv,
+				  unsigned int brightness)
+{
+	int err;
+
+	if (brightness == 0) {
+		priv->blink = REG_DISPLAY_SETUP_BLINK_OFF;
+		return ht16k33_display_off(priv);
+	}
+
+	err = ht16k33_display_on(priv);
+	if (err)
+		return err;
+
+	return i2c_smbus_write_byte(priv->client,
+				    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;
 
-	schedule_delayed_work(&fbdev->work, HZ / fbdev->refresh_rate);
+	schedule_delayed_work(&priv->work, HZ / fbdev->refresh_rate);
 }
 
 /*
···
  */
 static void ht16k33_fb_update(struct work_struct *work)
 {
-	struct ht16k33_fbdev *fbdev =
-		container_of(work, struct ht16k33_fbdev, work.work);
-	struct ht16k33_priv *priv =
-		container_of(fbdev, struct ht16k33_priv, fbdev);
+	struct ht16k33_priv *priv = container_of(work, struct ht16k33_priv,
+						 work.work);
+	struct ht16k33_fbdev *fbdev = &priv->fbdev;
 
 	uint8_t *p1, *p2;
 	int len, pos = 0, first = -1;
···
 
 static int ht16k33_initialize(struct ht16k33_priv *priv)
 {
+	uint8_t data[HT16K33_FB_SIZE];
 	uint8_t byte;
 	int err;
-	uint8_t data[HT16K33_MATRIX_LED_MAX_COLS * 2];
 
 	/* Clear RAM (8 * 16 bits) */
 	memset(data, 0, sizeof(data));
···
 
 	if (bl->props.power != FB_BLANK_UNBLANK ||
 	    bl->props.fb_blank != FB_BLANK_UNBLANK ||
-	    bl->props.state & BL_CORE_FBBLANK || brightness == 0) {
-		return ht16k33_display_off(priv);
-	}
+	    bl->props.state & BL_CORE_FBBLANK)
+		brightness = 0;
 
-	ht16k33_display_on(priv);
-	return i2c_smbus_write_byte(priv->client,
-				    REG_BRIGHTNESS | (brightness - 1));
+	return ht16k33_brightness_set(priv, brightness);
 }
 
 static int ht16k33_bl_check_fb(struct backlight_device *bl, struct fb_info *fi)
···
 	.check_fb	= ht16k33_bl_check_fb,
 };
 
+/*
+ * Blank events will be passed to the actual device handling the backlight when
+ * we return zero here.
+ */
+static int ht16k33_blank(int blank, struct fb_info *info)
+{
+	return 0;
+}
+
 static int ht16k33_mmap(struct fb_info *info, struct vm_area_struct *vma)
 {
 	struct ht16k33_priv *priv = info->par;
···
 	.owner = THIS_MODULE,
 	.fb_read = fb_sys_read,
 	.fb_write = fb_sys_write,
+	.fb_blank = ht16k33_blank,
 	.fb_fillrect = sys_fillrect,
 	.fb_copyarea = sys_copyarea,
 	.fb_imageblit = sys_imageblit,
···
 	disable_irq(keypad->client->irq);
 }
 
+static void ht16k33_linedisp_update(struct linedisp *linedisp)
+{
+	struct ht16k33_priv *priv = container_of(linedisp, struct ht16k33_priv,
+						 seg.linedisp);
+
+	schedule_delayed_work(&priv->work, 0);
+}
+
+static void ht16k33_seg7_update(struct work_struct *work)
+{
+	struct ht16k33_priv *priv = container_of(work, struct ht16k33_priv,
+						 work.work);
+	struct ht16k33_seg *seg = &priv->seg;
+	char *s = seg->curr;
+	uint8_t buf[9];
+
+	buf[0] = map_to_seg7(&seg->map.seg7, *s++);
+	buf[1] = 0;
+	buf[2] = map_to_seg7(&seg->map.seg7, *s++);
+	buf[3] = 0;
+	buf[4] = 0;
+	buf[5] = 0;
+	buf[6] = map_to_seg7(&seg->map.seg7, *s++);
+	buf[7] = 0;
+	buf[8] = map_to_seg7(&seg->map.seg7, *s++);
+
+	i2c_smbus_write_i2c_block_data(priv->client, 0, ARRAY_SIZE(buf), buf);
+}
+
+static void ht16k33_seg14_update(struct work_struct *work)
+{
+	struct ht16k33_priv *priv = container_of(work, struct ht16k33_priv,
+						 work.work);
+	struct ht16k33_seg *seg = &priv->seg;
+	char *s = seg->curr;
+	uint8_t buf[8];
+
+	put_unaligned_le16(map_to_seg14(&seg->map.seg14, *s++), buf);
+	put_unaligned_le16(map_to_seg14(&seg->map.seg14, *s++), buf + 2);
+	put_unaligned_le16(map_to_seg14(&seg->map.seg14, *s++), buf + 4);
+	put_unaligned_le16(map_to_seg14(&seg->map.seg14, *s++), buf + 6);
+
+	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 = {};
+	int err;
+
+	/* The LED is optional */
+	init_data.fwnode = device_get_named_child_node(dev, "led");
+	if (!init_data.fwnode)
+		return 0;
+
+	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)
 {
-	struct device_node *node = client->dev.of_node;
+	struct device *dev = &client->dev;
 	u32 rows = HT16K33_MATRIX_KEYPAD_MAX_ROWS;
 	u32 cols = HT16K33_MATRIX_KEYPAD_MAX_COLS;
 	int err;
···
 	keypad->client = client;
 	init_waitqueue_head(&keypad->wait);
 
-	keypad->dev = devm_input_allocate_device(&client->dev);
+	keypad->dev = devm_input_allocate_device(dev);
 	if (!keypad->dev)
 		return -ENOMEM;
 
···
 	keypad->dev->open = ht16k33_keypad_start;
 	keypad->dev->close = ht16k33_keypad_stop;
 
-	if (!of_get_property(node, "linux,no-autorepeat", NULL))
+	if (!device_property_read_bool(dev, "linux,no-autorepeat"))
 		__set_bit(EV_REP, keypad->dev->evbit);
 
-	err = of_property_read_u32(node, "debounce-delay-ms",
-				   &keypad->debounce_ms);
+	err = device_property_read_u32(dev, "debounce-delay-ms",
+				       &keypad->debounce_ms);
 	if (err) {
-		dev_err(&client->dev, "key debounce delay not specified\n");
+		dev_err(dev, "key debounce delay not specified\n");
 		return err;
 	}
 
-	err = matrix_keypad_parse_of_params(&client->dev, &rows, &cols);
+	err = matrix_keypad_parse_properties(dev, &rows, &cols);
 	if (err)
 		return err;
 	if (rows > HT16K33_MATRIX_KEYPAD_MAX_ROWS ||
 	    cols > HT16K33_MATRIX_KEYPAD_MAX_COLS) {
-		dev_err(&client->dev, "%u rows or %u cols out of range in DT\n",
-			rows, cols);
+		dev_err(dev, "%u rows or %u cols out of range in DT\n", rows,
+			cols);
 		return -ERANGE;
 	}
 
···
 	err = matrix_keypad_build_keymap(NULL, NULL, rows, cols, NULL,
 					 keypad->dev);
 	if (err) {
-		dev_err(&client->dev, "failed to build keymap\n");
+		dev_err(dev, "failed to build keymap\n");
 		return err;
 	}
 
-	err = devm_request_threaded_irq(&client->dev, client->irq,
-					NULL, ht16k33_keypad_irq_thread,
+	err = devm_request_threaded_irq(dev, client->irq, NULL,
+					ht16k33_keypad_irq_thread,
 					IRQF_TRIGGER_HIGH | IRQF_ONESHOT,
 					DRIVER_NAME, keypad);
 	if (err) {
-		dev_err(&client->dev, "irq request failed %d, error %d\n",
-			client->irq, err);
+		dev_err(dev, "irq request failed %d, error %d\n", client->irq,
+			err);
 		return err;
 	}
 
 	ht16k33_keypad_stop(keypad->dev);
 
-	err = input_register_device(keypad->dev);
-	if (err)
-		return err;
-
-	return 0;
+	return input_register_device(keypad->dev);
 }
 
-static int ht16k33_probe(struct i2c_client *client,
-				  const struct i2c_device_id *id)
+static int ht16k33_fbdev_probe(struct device *dev, struct ht16k33_priv *priv,
+			       uint32_t brightness)
 {
+	struct ht16k33_fbdev *fbdev = &priv->fbdev;
+	struct backlight_device *bl = NULL;
 	int err;
-	uint32_t dft_brightness;
-	struct backlight_device *bl;
-	struct backlight_properties bl_props;
-	struct ht16k33_priv *priv;
-	struct ht16k33_fbdev *fbdev;
-	struct device_node *node = client->dev.of_node;
 
-	if (!i2c_check_functionality(client->adapter, I2C_FUNC_I2C)) {
-		dev_err(&client->dev, "i2c_check_functionality error\n");
-		return -EIO;
+	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);
+		if (IS_ERR(bl)) {
+			dev_err(dev, "failed to register backlight\n");
+			return PTR_ERR(bl);
+		}
+
+		bl->props.brightness = brightness;
+		ht16k33_bl_update_status(bl);
 	}
-
-	priv = devm_kzalloc(&client->dev, sizeof(*priv), GFP_KERNEL);
-	if (!priv)
-		return -ENOMEM;
-
-	priv->client = client;
-	i2c_set_clientdata(client, priv);
-	fbdev = &priv->fbdev;
-
-	err = ht16k33_initialize(priv);
-	if (err)
-		return err;
 
 	/* Framebuffer (2 bytes per column) */
 	BUILD_BUG_ON(PAGE_SIZE < HT16K33_FB_SIZE);
···
 	if (!fbdev->buffer)
 		return -ENOMEM;
 
-	fbdev->cache = devm_kmalloc(&client->dev, HT16K33_FB_SIZE, GFP_KERNEL);
+	fbdev->cache = devm_kmalloc(dev, HT16K33_FB_SIZE, GFP_KERNEL);
 	if (!fbdev->cache) {
 		err = -ENOMEM;
 		goto err_fbdev_buffer;
 	}
 
-	fbdev->info = framebuffer_alloc(0, &client->dev);
+	fbdev->info = framebuffer_alloc(0, dev);
 	if (!fbdev->info) {
 		err = -ENOMEM;
 		goto err_fbdev_buffer;
 	}
 
-	err = of_property_read_u32(node, "refresh-rate-hz",
-		&fbdev->refresh_rate);
+	err = device_property_read_u32(dev, "refresh-rate-hz",
+				       &fbdev->refresh_rate);
 	if (err) {
-		dev_err(&client->dev, "refresh rate not specified\n");
+		dev_err(dev, "refresh rate not specified\n");
 		goto err_fbdev_info;
 	}
 	fb_bl_default_curve(fbdev->info, 0, MIN_BRIGHTNESS, MAX_BRIGHTNESS);
 
-	INIT_DELAYED_WORK(&fbdev->work, ht16k33_fb_update);
+	INIT_DELAYED_WORK(&priv->work, ht16k33_fb_update);
 	fbdev->info->fbops = &ht16k33_fb_ops;
 	fbdev->info->screen_base = (char __iomem *) fbdev->buffer;
 	fbdev->info->screen_size = HT16K33_FB_SIZE;
 	fbdev->info->fix = ht16k33_fb_fix;
 	fbdev->info->var = ht16k33_fb_var;
+	fbdev->info->bl_dev = bl;
 	fbdev->info->pseudo_palette = NULL;
 	fbdev->info->flags = FBINFO_FLAG_DEFAULT;
 	fbdev->info->par = priv;
···
 	if (err)
 		goto err_fbdev_info;
 
-	/* Keypad */
-	if (client->irq > 0) {
-		err = ht16k33_keypad_probe(client, &priv->keypad);
-		if (err)
-			goto err_fbdev_unregister;
-	}
-
-	/* Backlight */
-	memset(&bl_props, 0, sizeof(struct backlight_properties));
-	bl_props.type = BACKLIGHT_RAW;
-	bl_props.max_brightness = MAX_BRIGHTNESS;
-
-	bl = devm_backlight_device_register(&client->dev, DRIVER_NAME"-bl",
-					    &client->dev, priv,
-					    &ht16k33_bl_ops, &bl_props);
-	if (IS_ERR(bl)) {
-		dev_err(&client->dev, "failed to register backlight\n");
-		err = PTR_ERR(bl);
-		goto err_fbdev_unregister;
-	}
-
-	err = of_property_read_u32(node, "default-brightness-level",
-				   &dft_brightness);
-	if (err) {
-		dft_brightness = MAX_BRIGHTNESS;
-	} else if (dft_brightness > MAX_BRIGHTNESS) {
-		dev_warn(&client->dev,
-			 "invalid default brightness level: %u, using %u\n",
-			 dft_brightness, MAX_BRIGHTNESS);
-		dft_brightness = MAX_BRIGHTNESS;
-	}
-
-	bl->props.brightness = dft_brightness;
-	ht16k33_bl_update_status(bl);
-
 	ht16k33_fb_queue(priv);
 	return 0;
 
-err_fbdev_unregister:
-	unregister_framebuffer(fbdev->info);
 err_fbdev_info:
 	framebuffer_release(fbdev->info);
 err_fbdev_buffer:
···
 	return err;
 }
 
+static int ht16k33_seg_probe(struct device *dev, struct ht16k33_priv *priv,
+			     uint32_t brightness)
+{
+	struct ht16k33_seg *seg = &priv->seg;
+	int err;
+
+	err = ht16k33_brightness_set(priv, brightness);
+	if (err)
+		return err;
+
+	switch (priv->type) {
+	case DISP_MATRIX:
+		/* not handled here */
+		err = -EINVAL;
+		break;
+
+	case DISP_QUAD_7SEG:
+		INIT_DELAYED_WORK(&priv->work, ht16k33_seg7_update);
+		seg->map.seg7 = initial_map_seg7;
+		seg->map_size = sizeof(seg->map.seg7);
+		err = device_create_file(dev, &dev_attr_map_seg7);
+		break;
+
+	case DISP_QUAD_14SEG:
+		INIT_DELAYED_WORK(&priv->work, ht16k33_seg14_update);
+		seg->map.seg14 = initial_map_seg14;
+		seg->map_size = sizeof(seg->map.seg14);
+		err = device_create_file(dev, &dev_attr_map_seg14);
+		break;
+	}
+	if (err)
+		return err;
+
+	err = linedisp_register(&seg->linedisp, dev, 4, seg->curr,
+				ht16k33_linedisp_update);
+	if (err)
+		goto err_remove_map_file;
+
+	return 0;
+
+err_remove_map_file:
+	device_remove_file(dev, &dev_attr_map_seg7);
+	device_remove_file(dev, &dev_attr_map_seg14);
+	return err;
+}
+
+static int ht16k33_probe(struct i2c_client *client)
+{
+	struct device *dev = &client->dev;
+	const struct of_device_id *id;
+	struct ht16k33_priv *priv;
+	uint32_t dft_brightness;
+	int err;
+
+	if (!i2c_check_functionality(client->adapter, I2C_FUNC_I2C)) {
+		dev_err(dev, "i2c_check_functionality error\n");
+		return -EIO;
+	}
+
+	priv = devm_kzalloc(dev, sizeof(*priv), GFP_KERNEL);
+	if (!priv)
+		return -ENOMEM;
+
+	priv->client = client;
+	id = i2c_of_match_device(dev->driver->of_match_table, client);
+	if (id)
+		priv->type = (uintptr_t)id->data;
+	i2c_set_clientdata(client, priv);
+
+	err = ht16k33_initialize(priv);
+	if (err)
+		return err;
+
+	err = device_property_read_u32(dev, "default-brightness-level",
+				       &dft_brightness);
+	if (err) {
+		dft_brightness = MAX_BRIGHTNESS;
+	} else if (dft_brightness > MAX_BRIGHTNESS) {
+		dev_warn(dev,
+			 "invalid default brightness level: %u, using %u\n",
+			 dft_brightness, MAX_BRIGHTNESS);
+		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);
+		if (err)
+			return err;
+	}
+
+	switch (priv->type) {
+	case DISP_MATRIX:
+		/* Frame Buffer Display */
+		err = ht16k33_fbdev_probe(dev, priv, dft_brightness);
+		break;
+
+	case DISP_QUAD_7SEG:
+	case DISP_QUAD_14SEG:
+		/* Segment Display */
+		err = ht16k33_seg_probe(dev, priv, dft_brightness);
+		break;
+	}
+	return err;
+}
+
 static int ht16k33_remove(struct i2c_client *client)
 {
 	struct ht16k33_priv *priv = i2c_get_clientdata(client);
 	struct ht16k33_fbdev *fbdev = &priv->fbdev;
 
-	cancel_delayed_work_sync(&fbdev->work);
-	unregister_framebuffer(fbdev->info);
-	framebuffer_release(fbdev->info);
-	free_page((unsigned long) fbdev->buffer);
+	cancel_delayed_work_sync(&priv->work);
+
+	switch (priv->type) {
+	case DISP_MATRIX:
+		unregister_framebuffer(fbdev->info);
+		framebuffer_release(fbdev->info);
+		free_page((unsigned long)fbdev->buffer);
+		break;
+
+	case DISP_QUAD_7SEG:
+	case DISP_QUAD_14SEG:
+		linedisp_unregister(&priv->seg.linedisp);
+		device_remove_file(&client->dev, &dev_attr_map_seg7);
+		device_remove_file(&client->dev, &dev_attr_map_seg14);
+		break;
+	}
 
 	return 0;
 }
···
 MODULE_DEVICE_TABLE(i2c, ht16k33_i2c_match);
 
 static const struct of_device_id ht16k33_of_match[] = {
-	{ .compatible = "holtek,ht16k33", },
+	{
+		/* 0.56" 4-Digit 7-Segment FeatherWing Display (Red) */
+		.compatible = "adafruit,3108", .data = (void *)DISP_QUAD_7SEG,
+	}, {
+		/* 0.54" Quad Alphanumeric FeatherWing Display (Red) */
+		.compatible = "adafruit,3130", .data = (void *)DISP_QUAD_14SEG,
+	}, {
+		/* Generic, assumed Dot-Matrix Display */
+		.compatible = "holtek,ht16k33", .data = (void *)DISP_MATRIX,
+	},
 	{ }
 };
 MODULE_DEVICE_TABLE(of, ht16k33_of_match);
 
 static struct i2c_driver ht16k33_driver = {
-	.probe		= ht16k33_probe,
+	.probe_new	= ht16k33_probe,
 	.remove		= ht16k33_remove,
 	.driver		= {
 		.name		= DRIVER_NAME,
-		.of_match_table	= of_match_ptr(ht16k33_of_match),
+		.of_match_table	= ht16k33_of_match,
 	},
 	.id_table = ht16k33_i2c_match,
 };

drivers/auxdisplay/img-ascii-lcd.c

···
  * Author: Paul Burton <[e-mail]>
  */
 
-#include <generated/utsrelease.h>
 #include <linux/kernel.h>
 #include <linux/io.h>
 #include <linux/mfd/syscon.h>
···
 #include <linux/platform_device.h>
 #include <linux/regmap.h>
 #include <linux/slab.h>
-#include <linux/sysfs.h>
+
+#include "line-display.h"
 
 struct img_ascii_lcd_ctx;
 
···
 struct img_ascii_lcd_config {
 	unsigned int num_chars;
 	bool external_regmap;
-	void (*update)(struct img_ascii_lcd_ctx *ctx);
+	void (*update)(struct linedisp *linedisp);
 };
 
 /**
  * struct img_ascii_lcd_ctx - Private data structure
- * @pdev: the ASCII LCD platform device
  * @base: the base address of the LCD registers
  * @regmap: the regmap through which LCD registers are accessed
  * @offset: the offset within regmap to the start of the LCD registers
  * @cfg: pointer to the LCD model configuration
- * @message: the full message to display or scroll on the LCD
- * @message_len: the length of the @message string
- * @scroll_pos: index of the first character of @message currently displayed
- * @scroll_rate: scroll interval in jiffies
- * @timer: timer used to implement scrolling
+ * @linedisp: line display structure
  * @curr: the string currently displayed on the LCD
  */
 struct img_ascii_lcd_ctx {
-	struct platform_device *pdev;
 	union {
 		void __iomem *base;
 		struct regmap *regmap;
 	};
 	u32 offset;
 	const struct img_ascii_lcd_config *cfg;
-	char *message;
-	unsigned int message_len;
-	unsigned int scroll_pos;
-	unsigned int scroll_rate;
-	struct timer_list timer;
+	struct linedisp linedisp;
 	char curr[] __aligned(8);
 };
 
···
  * MIPS Boston development board
  */
 
-static void boston_update(struct img_ascii_lcd_ctx *ctx)
+static void boston_update(struct linedisp *linedisp)
 {
+	struct img_ascii_lcd_ctx *ctx =
+		container_of(linedisp, struct img_ascii_lcd_ctx, linedisp);
 	ulong val;
 
 #if BITS_PER_LONG == 64
···
  * MIPS Malta development board
  */
 
-static void malta_update(struct img_ascii_lcd_ctx *ctx)
+static void malta_update(struct linedisp *linedisp)
 {
+	struct img_ascii_lcd_ctx *ctx =
+		container_of(linedisp, struct img_ascii_lcd_ctx, linedisp);
 	unsigned int i;
 	int err = 0;
 
-	for (i = 0; i < ctx->cfg->num_chars; i++) {
+	for (i = 0; i < linedisp->num_chars; i++) {
 		err = regmap_write(ctx->regmap,
 				   ctx->offset + (i * 8), ctx->curr[i]);
 		if (err)
···
 	return 0;
 }
 
-static void sead3_update(struct img_ascii_lcd_ctx *ctx)
+static void sead3_update(struct linedisp *linedisp)
 {
+	struct img_ascii_lcd_ctx *ctx =
+		container_of(linedisp, struct img_ascii_lcd_ctx, linedisp);
 	unsigned int i;
 	int err = 0;
 
-	for (i = 0; i < ctx->cfg->num_chars; i++) {
+	for (i = 0; i < linedisp->num_chars; i++) {
 		err = sead3_wait_lcd_idle(ctx);
 		if (err)
 			break;
···
 MODULE_DEVICE_TABLE(of, img_ascii_lcd_matches);
 
 /**
- * img_ascii_lcd_scroll() - scroll the display by a character
- * @t: really a pointer to the private data structure
- *
- * Scroll the current message along the LCD by one character, rearming the
- * timer if required.
- */
-static void img_ascii_lcd_scroll(struct timer_list *t)
-{
-	struct img_ascii_lcd_ctx *ctx = from_timer(ctx, t, timer);
-	unsigned int i, ch = ctx->scroll_pos;
-	unsigned int num_chars = ctx->cfg->num_chars;
-
-	/* update the current message string */
-	for (i = 0; i < num_chars;) {
-		/* copy as many characters from the string as possible */
-		for (; i < num_chars && ch < ctx->message_len; i++, ch++)
-			ctx->curr[i] = ctx->message[ch];
-
-		/* wrap around to the start of the string */
-		ch = 0;
-	}
-
-	/* update the LCD */
-	ctx->cfg->update(ctx);
-
-	/* move on to the next character */
-	ctx->scroll_pos++;
-	ctx->scroll_pos %= ctx->message_len;
-
-	/* rearm the timer */
-	if (ctx->message_len > ctx->cfg->num_chars)
-		mod_timer(&ctx->timer, jiffies + ctx->scroll_rate);
-}
-
-/**
- * img_ascii_lcd_display() - set the message to be displayed
- * @ctx: pointer to the private data structure
- * @msg: the message to display
- * @count: length of msg, or -1
- *
- * Display a new message @msg on the LCD. @msg can be longer than the number of
- * characters the LCD can display, in which case it will begin scrolling across
- * the LCD display.
- *
- * Return: 0 on success, -ENOMEM on memory allocation failure
- */
-static int img_ascii_lcd_display(struct img_ascii_lcd_ctx *ctx,
-			     const char *msg, ssize_t count)
-{
-	char *new_msg;
-
-	/* stop the scroll timer */
-	del_timer_sync(&ctx->timer);
-
-	if (count == -1)
-		count = strlen(msg);
-
-	/* if the string ends with a newline, trim it */
-	if (msg[count - 1] == '\n')
-		count--;
-
-	new_msg = devm_kmalloc(&ctx->pdev->dev, count + 1, GFP_KERNEL);
-	if (!new_msg)
-		return -ENOMEM;
-
-	memcpy(new_msg, msg, count);
-	new_msg[count] = 0;
-
-	if (ctx->message)
-		devm_kfree(&ctx->pdev->dev, ctx->message);
-
-	ctx->message = new_msg;
-	ctx->message_len = count;
-	ctx->scroll_pos = 0;
-
-	/* update the LCD */
-	img_ascii_lcd_scroll(&ctx->timer);
-
-	return 0;
-}
-
-/**
- * message_show() - read message via sysfs
- * @dev: the LCD device
- * @attr: the LCD message attribute
- * @buf: the buffer to read the message into
- *
- * Read the current message being displayed or scrolled across the LCD display
- * into @buf, for reads from sysfs.
- *
- * Return: the number of characters written to @buf
- */
-static ssize_t message_show(struct device *dev, struct device_attribute *attr,
-			    char *buf)
-{
-	struct img_ascii_lcd_ctx *ctx = dev_get_drvdata(dev);
-
-	return sprintf(buf, "%s\n", ctx->message);
-}
-
-/**
- * message_store() - write a new message via sysfs
- * @dev: the LCD device
- * @attr: the LCD message attribute
- * @buf: the buffer containing the new message
- * @count: the size of the message in @buf
- *
- * Write a new message to display or scroll across the LCD display from sysfs.
- *
- * Return: the size of the message on success, else -ERRNO
- */
-static ssize_t message_store(struct device *dev, struct device_attribute *attr,
-			     const char *buf, size_t count)
-{
-	struct img_ascii_lcd_ctx *ctx = dev_get_drvdata(dev);
-	int err;
-
-	err = img_ascii_lcd_display(ctx, buf, count);
-	return err ?: count;
-}
-
-static DEVICE_ATTR_RW(message);
-
-/**
  * img_ascii_lcd_probe() - probe an LCD display device
  * @pdev: the LCD platform device
  *
···
 {
 	const struct of_device_id *match;
 	const struct img_ascii_lcd_config *cfg;
+	struct device *dev = &pdev->dev;
 	struct img_ascii_lcd_ctx *ctx;
 	int err;
 
-	match = of_match_device(img_ascii_lcd_matches, &pdev->dev);
+	match = of_match_device(img_ascii_lcd_matches, dev);
 	if (!match)
 		return -ENODEV;
 
 	cfg = match->data;
-	ctx = devm_kzalloc(&pdev->dev, sizeof(*ctx) + cfg->num_chars,
-			   GFP_KERNEL);
+	ctx = devm_kzalloc(dev, sizeof(*ctx) + cfg->num_chars, GFP_KERNEL);
 	if (!ctx)
 		return -ENOMEM;
 
 	if (cfg->external_regmap) {
-		ctx->regmap = syscon_node_to_regmap(pdev->dev.parent->of_node);
+		ctx->regmap = syscon_node_to_regmap(dev->parent->of_node);
 		if (IS_ERR(ctx->regmap))
 			return PTR_ERR(ctx->regmap);
 
-		if (of_property_read_u32(pdev->dev.of_node, "offset",
-					 &ctx->offset))
+		if (of_property_read_u32(dev->of_node, "offset", &ctx->offset))
 			return -EINVAL;
 	} else {
 		ctx->base = devm_platform_ioremap_resource(pdev, 0);
···
 			return PTR_ERR(ctx->base);
 	}
 
-	ctx->pdev = pdev;
-	ctx->cfg = cfg;
-	ctx->message = NULL;
-	ctx->scroll_pos = 0;
-	ctx->scroll_rate = HZ / 2;
+	err = linedisp_register(&ctx->linedisp, dev, cfg->num_chars, ctx->curr,
+				cfg->update);
+	if (err)
+		return err;
 
-	/* initialise a timer for scrolling the message */
-	timer_setup(&ctx->timer, img_ascii_lcd_scroll, 0);
+	/* for backwards compatibility */
+	err = compat_only_sysfs_link_entry_to_kobj(&dev->kobj,
+						   &ctx->linedisp.dev.kobj,
+						   "message", NULL);
+	if (err)
+		goto err_unregister;
 
 	platform_set_drvdata(pdev, ctx);
-
-	/* display a default message */
-	err = img_ascii_lcd_display(ctx, "Linux " UTS_RELEASE "       ", -1);
-	if (err)
-		goto out_del_timer;
-
-	err = device_create_file(&pdev->dev, &dev_attr_message);
-	if (err)
-		goto out_del_timer;
-
 	return 0;
-out_del_timer:
-	del_timer_sync(&ctx->timer);
+
+err_unregister:
+	linedisp_unregister(&ctx->linedisp);
 	return err;
 }
 
···
 {
 	struct img_ascii_lcd_ctx *ctx = platform_get_drvdata(pdev);
 
-	device_remove_file(&pdev->dev, &dev_attr_message);
-	del_timer_sync(&ctx->timer);
+	sysfs_remove_link(&pdev->dev.kobj, "message");
+	linedisp_unregister(&ctx->linedisp);
 	return 0;
 }
 

drivers/auxdisplay/ks0108.c

···
 #include <linux/module.h>
 #include <linux/kernel.h>
 #include <linux/delay.h>
-#include <linux/fs.h>
-#include <linux/io.h>
 #include <linux/parport.h>
-#include <linux/uaccess.h>
 #include <linux/ks0108.h>
 
 #define KS0108_NAME "ks0108"

drivers/auxdisplay/line-display.c

···
+// SPDX-License-Identifier: GPL-2.0-or-later
+/*
+ * Character line display core support
+ *
+ * Copyright (C) 2016 Imagination Technologies
+ * Author: Paul Burton <[e-mail]>
+ *
+ * Copyright (C) 2021 Glider bv
+ */
+
+#include <generated/utsrelease.h>
+
+#include <linux/device.h>
+#include <linux/module.h>
+#include <linux/slab.h>
+#include <linux/string.h>
+#include <linux/sysfs.h>
+#include <linux/timer.h>
+
+#include "line-display.h"
+
+#define DEFAULT_SCROLL_RATE	(HZ / 2)
+
+/**
+ * linedisp_scroll() - scroll the display by a character
+ * @t: really a pointer to the private data structure
+ *
+ * Scroll the current message along the display by one character, rearming the
+ * timer if required.
+ */
+static void linedisp_scroll(struct timer_list *t)
+{
+	struct linedisp *linedisp = from_timer(linedisp, t, timer);
+	unsigned int i, ch = linedisp->scroll_pos;
+	unsigned int num_chars = linedisp->num_chars;
+
+	/* update the current message string */
+	for (i = 0; i < num_chars;) {
+		/* copy as many characters from the string as possible */
+		for (; i < num_chars && ch < linedisp->message_len; i++, ch++)
+			linedisp->buf[i] = linedisp->message[ch];
+
+		/* wrap around to the start of the string */
+		ch = 0;
+	}
+
+	/* update the display */
+	linedisp->update(linedisp);
+
+	/* move on to the next character */
+	linedisp->scroll_pos++;
+	linedisp->scroll_pos %= linedisp->message_len;
+
+	/* rearm the timer */
+	if (linedisp->message_len > num_chars && linedisp->scroll_rate)
+		mod_timer(&linedisp->timer, jiffies + linedisp->scroll_rate);
+}
+
+/**
+ * linedisp_display() - set the message to be displayed
+ * @linedisp: pointer to the private data structure
+ * @msg: the message to display
+ * @count: length of msg, or -1
+ *
+ * Display a new message @msg on the display. @msg can be longer than the
+ * number of characters the display can display, in which case it will begin
+ * scrolling across the display.
+ *
+ * Return: 0 on success, -ENOMEM on memory allocation failure
+ */
+static int linedisp_display(struct linedisp *linedisp, const char *msg,
+			    ssize_t count)
+{
+	char *new_msg;
+
+	/* stop the scroll timer */
+	del_timer_sync(&linedisp->timer);
+
+	if (count == -1)
+		count = strlen(msg);
+
+	/* if the string ends with a newline, trim it */
+	if (msg[count - 1] == '\n')
+		count--;
+
+	if (!count) {
+		/* Clear the display */
+		kfree(linedisp->message);
+		linedisp->message = NULL;
+		linedisp->message_len = 0;
+		memset(linedisp->buf, ' ', linedisp->num_chars);
+		linedisp->update(linedisp);
+		return 0;
+	}
+
+	new_msg = kmemdup_nul(msg, count, GFP_KERNEL);
+	if (!new_msg)
+		return -ENOMEM;
+
+	kfree(linedisp->message);
+
+	linedisp->message = new_msg;
+	linedisp->message_len = count;
+	linedisp->scroll_pos = 0;
+
+	/* update the display */
+	linedisp_scroll(&linedisp->timer);
+
+	return 0;
+}
+
+/**
+ * message_show() - read message via sysfs
+ * @dev: the display device
+ * @attr: the display message attribute
+ * @buf: the buffer to read the message into
+ *
+ * Read the current message being displayed or scrolled across the display into
+ * @buf, for reads from sysfs.
+ *
+ * Return: the number of characters written to @buf
+ */
+static ssize_t message_show(struct device *dev, struct device_attribute *attr,
+			    char *buf)
+{
+	struct linedisp *linedisp = container_of(dev, struct linedisp, dev);
+
+	return sysfs_emit(buf, "%s\n", linedisp->message);
+}
+
+/**
+ * message_store() - write a new message via sysfs
+ * @dev: the display device
+ * @attr: the display message attribute
+ * @buf: the buffer containing the new message
+ * @count: the size of the message in @buf
+ *
+ * Write a new message to display or scroll across the display from sysfs.
+ *
+ * Return: the size of the message on success, else -ERRNO
+ */
+static ssize_t message_store(struct device *dev, struct device_attribute *attr,
+			     const char *buf, size_t count)
+{
+	struct linedisp *linedisp = container_of(dev, struct linedisp, dev);
+	int err;
+
+	err = linedisp_display(linedisp, buf, count);
+	return err ?: count;
+}
+
+static DEVICE_ATTR_RW(message);
+
+static ssize_t scroll_step_ms_show(struct device *dev,
+				   struct device_attribute *attr, char *buf)
+{
+	struct linedisp *linedisp = container_of(dev, struct linedisp, dev);
+
+	return sysfs_emit(buf, "%u\n", jiffies_to_msecs(linedisp->scroll_rate));
+}
+
+static ssize_t scroll_step_ms_store(struct device *dev,
+				    struct device_attribute *attr,
+				    const char *buf, size_t count)
+{
+	struct linedisp *linedisp = container_of(dev, struct linedisp, dev);
+	unsigned int ms;
+
+	if (kstrtouint(buf, 10, &ms) != 0)
+		return -EINVAL;
+
+	linedisp->scroll_rate = msecs_to_jiffies(ms);
+	if (linedisp->message && linedisp->message_len > linedisp->num_chars) {
+		del_timer_sync(&linedisp->timer);
+		if (linedisp->scroll_rate)
+			linedisp_scroll(&linedisp->timer);
+	}
+
+	return count;
+}
+
+static DEVICE_ATTR_RW(scroll_step_ms);
+
+static struct attribute *linedisp_attrs[] = {
+	&dev_attr_message.attr,
+	&dev_attr_scroll_step_ms.attr,
+	NULL,
+};
+ATTRIBUTE_GROUPS(linedisp);
+
+static const struct device_type linedisp_type = {
+	.groups	= linedisp_groups,
+};
+
+/**
+ * linedisp_register - register a character line display
+ * @linedisp: pointer to character line display structure
+ * @parent: parent device
+ * @num_chars: the number of characters that can be displayed
+ * @buf: pointer to a buffer that can hold @num_chars characters
+ * @update: Function called to update the display.  This must not sleep!
+ *
+ * Return: zero on success, else a negative error code.
+ */
+int linedisp_register(struct linedisp *linedisp, struct device *parent,
+		      unsigned int num_chars, char *buf,
+		      void (*update)(struct linedisp *linedisp))
+{
+	static atomic_t linedisp_id = ATOMIC_INIT(-1);
+	int err;
+
+	memset(linedisp, 0, sizeof(*linedisp));
+	linedisp->dev.parent = parent;
+	linedisp->dev.type = &linedisp_type;
+	linedisp->update = update;
+	linedisp->buf = buf;
+	linedisp->num_chars = num_chars;
+	linedisp->scroll_rate = DEFAULT_SCROLL_RATE;
+
+	device_initialize(&linedisp->dev);
+	dev_set_name(&linedisp->dev, "linedisp.%lu",
+		     (unsigned long)atomic_inc_return(&linedisp_id));
+
+	/* initialise a timer for scrolling the message */
+	timer_setup(&linedisp->timer, linedisp_scroll, 0);
+
+	err = device_add(&linedisp->dev);
+	if (err)
+		goto out_del_timer;
+
+	/* display a default message */
+	err = linedisp_display(linedisp, "Linux " UTS_RELEASE "       ", -1);
+	if (err)
+		goto out_del_dev;
+
+	return 0;
+
+out_del_dev:
+	device_del(&linedisp->dev);
+out_del_timer:
+	del_timer_sync(&linedisp->timer);
+	put_device(&linedisp->dev);
+	return err;
+}
+EXPORT_SYMBOL_GPL(linedisp_register);
+
+/**
+ * linedisp_unregister - unregister a character line display
+ * @linedisp: pointer to character line display structure registered previously
+ *	      with linedisp_register()
+ */
+void linedisp_unregister(struct linedisp *linedisp)
+{
+	device_del(&linedisp->dev);
+	del_timer_sync(&linedisp->timer);
+	kfree(linedisp->message);
+	put_device(&linedisp->dev);
+}
+EXPORT_SYMBOL_GPL(linedisp_unregister);
+
+MODULE_LICENSE("GPL");

drivers/auxdisplay/line-display.h

···
+/* SPDX-License-Identifier: GPL-2.0-or-later */
+/*
+ * Character line display core support
+ *
+ * Copyright (C) 2016 Imagination Technologies
+ * Author: Paul Burton <[e-mail]>
+ *
+ * Copyright (C) 2021 Glider bv
+ */
+
+#ifndef _LINEDISP_H
+#define _LINEDISP_H
+
+/**
+ * struct linedisp - character line display private data structure
+ * @dev: the line display device
+ * @timer: timer used to implement scrolling
+ * @update: function called to update the display
+ * @buf: pointer to the buffer for the string currently displayed
+ * @message: the full message to display or scroll on the display
+ * @num_chars: the number of characters that can be displayed
+ * @message_len: the length of the @message string
+ * @scroll_pos: index of the first character of @message currently displayed
+ * @scroll_rate: scroll interval in jiffies
+ */
+struct linedisp {
+	struct device dev;
+	struct timer_list timer;
+	void (*update)(struct linedisp *linedisp);
+	char *buf;
+	char *message;
+	unsigned int num_chars;
+	unsigned int message_len;
+	unsigned int scroll_pos;
+	unsigned int scroll_rate;
+};
+
+int linedisp_register(struct linedisp *linedisp, struct device *parent,
+		      unsigned int num_chars, char *buf,
+		      void (*update)(struct linedisp *linedisp));
+void linedisp_unregister(struct linedisp *linedisp);
+
+#endif /* LINEDISP_H */

include/uapi/linux/map_to_14segment.h

···
+/* SPDX-License-Identifier: GPL-2.0+ WITH Linux-syscall-note */
+/*
+ * Copyright (C) 2021 Glider bv
+ *
+ * Based on include/uapi/linux/map_to_7segment.h:
+
+ * Copyright (c) 2005 Henk Vergonet <[e-mail]>
+ */
+
+#ifndef MAP_TO_14SEGMENT_H
+#define MAP_TO_14SEGMENT_H
+
+/* This file provides translation primitives and tables for the conversion
+ * of (ASCII) characters to a 14-segments notation.
+ *
+ * The 14 segment's wikipedia notation below is used as standard.
+ * See: https://en.wikipedia.org/wiki/Fourteen-segment_display
+ *
+ * Notation:	+---a---+
+ *		|\  |  /|
+ *		f h i j b
+ *		|  \|/  |
+ *		+-g1+-g2+
+ *		|  /|\  |
+ *		e k l m c
+ *		|/  |  \|
+ *		+---d---+
+ *
+ * Usage:
+ *
+ *   Register a map variable, and fill it with a character set:
+ *	static SEG14_DEFAULT_MAP(map_seg14);
+ *
+ *
+ *   Then use for conversion:
+ *	seg14 = map_to_seg14(&map_seg14, some_char);
+ *	...
+ *
+ * In device drivers it is recommended, if required, to make the char map
+ * accessible via the sysfs interface using the following scheme:
+ *
+ * static ssize_t map_seg14_show(struct device *dev,
+ *				 struct device_attribute *attr, char *buf)
+ * {
+ *	memcpy(buf, &map_seg14, sizeof(map_seg14));
+ *	return sizeof(map_seg14);
+ * }
+ * static ssize_t map_seg14_store(struct device *dev,
+ *				  struct device_attribute *attr,
+ *				  const char *buf, size_t cnt)
+ * {
+ *	if (cnt != sizeof(map_seg14))
+ *		return -EINVAL;
+ *	memcpy(&map_seg14, buf, cnt);
+ *	return cnt;
+ * }
+ * static DEVICE_ATTR_RW(map_seg14);
+ */
+#include <linux/errno.h>
+#include <linux/types.h>
+
+#include <asm/byteorder.h>
+
+#define BIT_SEG14_A		0
+#define BIT_SEG14_B		1
+#define BIT_SEG14_C		2
+#define BIT_SEG14_D		3
+#define BIT_SEG14_E		4
+#define BIT_SEG14_F		5
+#define BIT_SEG14_G1		6
+#define BIT_SEG14_G2		7
+#define BIT_SEG14_H		8
+#define BIT_SEG14_I		9
+#define BIT_SEG14_J		10
+#define BIT_SEG14_K		11
+#define BIT_SEG14_L		12
+#define BIT_SEG14_M		13
+#define BIT_SEG14_RESERVED1	14
+#define BIT_SEG14_RESERVED2	15
+
+struct seg14_conversion_map {
+	__be16 table[128];
+};
+
+static __inline__ int map_to_seg14(struct seg14_conversion_map *map, int c)
+{
+	if (c < 0 || c >= sizeof(map->table) / sizeof(map->table[0]))
+		return -EINVAL;
+
+	return __be16_to_cpu(map->table[c]);
+}
+
+#define SEG14_CONVERSION_MAP(_name, _map)	\
+	struct seg14_conversion_map _name = { .table = { _map } }
+
+/*
+ * It is recommended to use a facility that allows user space to redefine
+ * custom character sets for LCD devices. Please use a sysfs interface
+ * as described above.
+ */
+#define MAP_TO_SEG14_SYSFS_FILE	"map_seg14"
+
+/*******************************************************************************
+ * ASCII conversion table
+ ******************************************************************************/
+
+#define _SEG14(sym, a, b, c, d, e, f, g1, g2, h, j, k, l, m, n)	\
+	__cpu_to_be16( a << BIT_SEG14_A  |  b << BIT_SEG14_B  |	\
+		       c << BIT_SEG14_C  |  d << BIT_SEG14_D  |	\
+		       e << BIT_SEG14_E  |  f << BIT_SEG14_F  |	\
+		      g1 << BIT_SEG14_G1 | g2 << BIT_SEG14_G2 |	\
+		       h << BIT_SEG14_H  |  j << BIT_SEG14_I  |	\
+		       k << BIT_SEG14_J  |  l << BIT_SEG14_K  |	\
+		       m << BIT_SEG14_L  |  n << BIT_SEG14_M )
+
+#define _MAP_0_32_ASCII_SEG14_NON_PRINTABLE				\
+	0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,
+
+#define _MAP_33_47_ASCII_SEG14_SYMBOL				\
+	_SEG14('!', 0, 1, 1, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0),	\
+	_SEG14('"', 0, 1, 0, 0, 0, 0, 0, 0, 0, 1, 0, 0, 0, 0),	\
+	_SEG14('#', 0, 1, 1, 1, 0, 0, 1, 1, 0, 1, 0, 0, 1, 0),	\
+	_SEG14('$', 1, 0, 1, 1, 0, 1, 1, 1, 0, 1, 0, 0, 1, 0),	\
+	_SEG14('%', 0, 0, 1, 0, 0, 1, 0, 0, 0, 0, 1, 1, 0, 0),	\
+	_SEG14('&', 1, 0, 0, 1, 1, 0, 1, 0, 1, 0, 1, 0, 0, 1),	\
+	_SEG14('\'',0, 0, 0, 0, 0, 0, 0, 0, 0, 1, 0, 0, 0, 0),	\
+	_SEG14('(', 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 1, 0, 0, 1),	\
+	_SEG14(')', 0, 0, 0, 0, 0, 0, 0, 0, 1, 0, 0, 1, 0, 0),	\
+	_SEG14('*', 0, 0, 0, 0, 0, 0, 0, 0, 1, 1, 1, 1, 1, 1),	\
+	_SEG14('+', 0, 0, 0, 0, 0, 0, 1, 1, 0, 1, 0, 0, 1, 0),	\
+	_SEG14(',', 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 1, 0, 0),	\
+	_SEG14('-', 0, 0, 0, 0, 0, 0, 1, 1, 0, 0, 0, 0, 0, 0),	\
+	_SEG14('.', 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 1),	\
+	_SEG14('/', 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 1, 1, 0, 0),
+
+#define _MAP_48_57_ASCII_SEG14_NUMERIC				\
+	_SEG14('0', 1, 1, 1, 1, 1, 1, 0, 0, 0, 0, 1, 1, 0, 0),	\
+	_SEG14('1', 0, 1, 1, 0, 0, 0, 0, 0, 0, 0, 1, 0, 0, 0),	\
+	_SEG14('2', 1, 1, 0, 1, 1, 0, 1, 1, 0, 0, 0, 0, 0, 0),	\
+	_SEG14('3', 1, 1, 1, 1, 0, 0, 0, 1, 0, 0, 0, 0, 0, 0),	\
+	_SEG14('4', 0, 1, 1, 0, 0, 1, 1, 1, 0, 0, 0, 0, 0, 0),	\
+	_SEG14('5', 1, 0, 0, 1, 0, 1, 1, 0, 0, 0, 0, 0, 0, 1),	\
+	_SEG14('6', 1, 0, 1, 1, 1, 1, 1, 1, 0, 0, 0, 0, 0, 0),	\
+	_SEG14('7', 1, 0, 0, 0, 0, 0, 0, 0, 0, 0, 1, 0, 1, 0),	\
+	_SEG14('8', 1, 1, 1, 1, 1, 1, 1, 1, 0, 0, 0, 0, 0, 0),	\
+	_SEG14('9', 1, 1, 1, 1, 0, 1, 1, 1, 0, 0, 0, 0, 0, 0),
+
+#define _MAP_58_64_ASCII_SEG14_SYMBOL				\
+	_SEG14(':', 0, 0, 0, 0, 0, 0, 0, 0, 0, 1, 0, 0, 1, 0),	\
+	_SEG14(';', 0, 0, 0, 0, 0, 0, 0, 0, 0, 1, 0, 1, 0, 0),	\
+	_SEG14('<', 0, 0, 0, 0, 0, 0, 1, 0, 0, 0, 1, 0, 0, 1),	\
+	_SEG14('=', 0, 0, 0, 1, 0, 0, 1, 1, 0, 0, 0, 0, 0, 0),	\
+	_SEG14('>', 0, 0, 0, 0, 0, 0, 0, 1, 1, 0, 0, 1, 0, 0),	\
+	_SEG14('?', 1, 0, 0, 0, 0, 1, 0, 0, 0, 0, 1, 0, 1, 0),	\
+	_SEG14('@', 1, 1, 0, 1, 1, 1, 0, 1, 0, 1, 0, 0, 0, 0),
+
+#define _MAP_65_90_ASCII_SEG14_ALPHA_UPPER			\
+	_SEG14('A', 1, 1, 1, 0, 1, 1, 1, 1, 0, 0, 0, 0, 0, 0),	\
+	_SEG14('B', 1, 1, 1, 1, 0, 0, 0, 1, 0, 1, 0, 0, 1, 0),	\
+	_SEG14('C', 1, 0, 0, 1, 1, 1, 0, 0, 0, 0, 0, 0, 0, 0),	\
+	_SEG14('D', 1, 1, 1, 1, 0, 0, 0, 0, 0, 1, 0, 0, 1, 0),	\
+	_SEG14('E', 1, 0, 0, 1, 1, 1, 1, 0, 0, 0, 0, 0, 0, 0),	\
+	_SEG14('F', 1, 0, 0, 0, 1, 1, 1, 0, 0, 0, 0, 0, 0, 0),	\
+	_SEG14('G', 1, 0, 1, 1, 1, 1, 0, 1, 0, 0, 0, 0, 0, 0),	\
+	_SEG14('H', 0, 1, 1, 0, 1, 1, 1, 1, 0, 0, 0, 0, 0, 0),	\
+	_SEG14('I', 1, 0, 0, 1, 0, 0, 0, 0, 0, 1, 0, 0, 1, 0),	\
+	_SEG14('J', 0, 1, 1, 1, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0),	\
+	_SEG14('K', 0, 0, 0, 0, 1, 1, 1, 0, 0, 0, 1, 0, 0, 1),	\
+	_SEG14('L', 0, 0, 0, 1, 1, 1, 0, 0, 0, 0, 0, 0, 0, 0),	\
+	_SEG14('M', 0, 1, 1, 0, 1, 1, 0, 0, 1, 0, 1, 0, 0, 0),	\
+	_SEG14('N', 0, 1, 1, 0, 1, 1, 0, 0, 1, 0, 0, 0, 0, 1),	\
+	_SEG14('O', 1, 1, 1, 1, 1, 1, 0, 0, 0, 0, 0, 0, 0, 0),	\
+	_SEG14('P', 1, 1, 0, 0, 1, 1, 1, 1, 0, 0, 0, 0, 0, 0),	\
+	_SEG14('Q', 1, 1, 1, 1, 1, 1, 0, 0, 0, 0, 0, 0, 0, 1),	\
+	_SEG14('R', 1, 1, 0, 0, 1, 1, 1, 1, 0, 0, 0, 0, 0, 1),	\
+	_SEG14('S', 1, 0, 1, 1, 0, 1, 1, 1, 0, 0, 0, 0, 0, 0),	\
+	_SEG14('T', 1, 0, 0, 0, 0, 0, 0, 0, 0, 1, 0, 0, 1, 0),	\
+	_SEG14('U', 0, 1, 1, 1, 1, 1, 0, 0, 0, 0, 0, 0, 0, 0),	\
+	_SEG14('V', 0, 0, 0, 0, 1, 1, 0, 0, 0, 0, 1, 1, 0, 0),	\
+	_SEG14('W', 0, 1, 1, 0, 1, 1, 0, 0, 0, 0, 0, 1, 0, 1),	\
+	_SEG14('X', 0, 0, 0, 0, 0, 0, 0, 0, 1, 0, 1, 1, 0, 1),	\
+	_SEG14('Y', 0, 0, 0, 0, 0, 0, 0, 0, 1, 0, 1, 0, 1, 0),	\
+	_SEG14('Z', 1, 0, 0, 1, 0, 0, 0, 0, 0, 0, 1, 1, 0, 0),
+
+#define _MAP_91_96_ASCII_SEG14_SYMBOL				\
+	_SEG14('[', 1, 0, 0, 1, 1, 1, 0, 0, 0, 0, 0, 0, 0, 0),	\
+	_SEG14('\\',0, 0, 0, 0, 0, 0, 0, 0, 1, 0, 0, 0, 0, 1),	\
+	_SEG14(']', 1, 1, 1, 1, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0),	\
+	_SEG14('^', 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 1, 0, 1),	\
+	_SEG14('_', 0, 0, 0, 1, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0),	\
+	_SEG14('`', 0, 0, 0, 0, 0, 0, 0, 0, 1, 0, 0, 0, 0, 0),
+
+#define _MAP_97_122_ASCII_SEG14_ALPHA_LOWER			\
+	_SEG14('a', 0, 0, 0, 1, 1, 0, 1, 0, 0, 0, 0, 0, 1, 0),	\
+	_SEG14('b', 0, 0, 0, 1, 1, 1, 1, 0, 0, 0, 0, 0, 0, 1),	\
+	_SEG14('c', 0, 0, 0, 1, 1, 0, 1, 1, 0, 0, 0, 0, 0, 0),	\
+	_SEG14('d', 0, 1, 1, 1, 0, 0, 0, 1, 0, 0, 0, 1, 0, 0),	\
+	_SEG14('e', 0, 0, 0, 1, 1, 0, 1, 0, 0, 0, 0, 1, 0, 0),	\
+	_SEG14('f', 0, 0, 0, 0, 0, 0, 1, 1, 0, 0, 1, 0, 1, 0),	\
+	_SEG14('g', 0, 1, 1, 1, 0, 0, 0, 1, 0, 0, 1, 0, 0, 0),	\
+	_SEG14('h', 0, 0, 0, 0, 1, 1, 1, 0, 0, 0, 0, 0, 1, 0),	\
+	_SEG14('i', 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 1, 0),	\
+	_SEG14('j', 0, 0, 0, 0, 1, 0, 0, 0, 0, 1, 0, 1, 0, 0),	\
+	_SEG14('k', 0, 0, 0, 0, 0, 0, 0, 0, 0, 1, 1, 0, 1, 1),	\
+	_SEG14('l', 0, 0, 0, 0, 1, 1, 0, 0, 0, 0, 0, 0, 0, 0),	\
+	_SEG14('m', 0, 0, 1, 0, 1, 0, 1, 1, 0, 0, 0, 0, 1, 0),	\
+	_SEG14('n', 0, 0, 0, 0, 1, 0, 1, 0, 0, 0, 0, 0, 1, 0),	\
+	_SEG14('o', 0, 0, 1, 1, 1, 0, 1, 1, 0, 0, 0, 0, 0, 0),	\
+	_SEG14('p', 0, 0, 0, 0, 1, 1, 1, 0, 1, 0, 0, 0, 0, 0),	\
+	_SEG14('q', 0, 1, 1, 0, 0, 0, 0, 1, 0, 0, 1, 0, 0, 0),	\
+	_SEG14('r', 0, 0, 0, 0, 1, 0, 1, 0, 0, 0, 0, 0, 0, 0),	\
+	_SEG14('s', 0, 0, 0, 1, 0, 0, 0, 1, 0, 0, 0, 0, 0, 1),	\
+	_SEG14('t', 0, 0, 0, 1, 1, 1, 1, 0, 0, 0, 0, 0, 0, 0),	\
+	_SEG14('u', 0, 0, 1, 1, 1, 0, 0, 0, 0, 0, 0, 0, 0, 0),	\
+	_SEG14('v', 0, 0, 0, 0, 1, 0, 0, 0, 0, 0, 0, 1, 0, 0),	\
+	_SEG14('w', 0, 0, 1, 0, 1, 0, 0, 0, 0, 0, 0, 1, 0, 1),	\
+	_SEG14('x', 0, 0, 0, 0, 0, 0, 1, 1, 0, 0, 0, 1, 0, 1),	\
+	_SEG14('y', 0, 1, 1, 1, 0, 0, 0, 1, 0, 1, 0, 0, 0, 0),	\
+	_SEG14('z', 0, 0, 0, 1, 0, 0, 1, 0, 0, 0, 0, 1, 0, 0),
+
+#define _MAP_123_126_ASCII_SEG14_SYMBOL				\
+	_SEG14('{', 1, 0, 0, 1, 0, 0, 1, 0, 1, 0, 0, 1, 0, 0),	\
+	_SEG14('|', 0, 0, 0, 0, 0, 0, 0, 0, 0, 1, 0, 0, 1, 0),	\
+	_SEG14('}', 1, 0, 0, 1, 0, 0, 0, 1, 0, 0, 1, 0, 0, 1),	\
+	_SEG14('~', 0, 0, 0, 0, 0, 0, 1, 1, 0, 0, 1, 1, 0, 0),
+
+/* Maps */
+#define MAP_ASCII14SEG_ALPHANUM			\
+	_MAP_0_32_ASCII_SEG14_NON_PRINTABLE	\
+	_MAP_33_47_ASCII_SEG14_SYMBOL		\
+	_MAP_48_57_ASCII_SEG14_NUMERIC		\
+	_MAP_58_64_ASCII_SEG14_SYMBOL		\
+	_MAP_65_90_ASCII_SEG14_ALPHA_UPPER	\
+	_MAP_91_96_ASCII_SEG14_SYMBOL		\
+	_MAP_97_122_ASCII_SEG14_ALPHA_LOWER	\
+	_MAP_123_126_ASCII_SEG14_SYMBOL
+
+#define SEG14_DEFAULT_MAP(_name)		\
+	SEG14_CONVERSION_MAP(_name, MAP_ASCII14SEG_ALPHANUM)
+
+#endif	/* MAP_TO_14SEGMENT_H */