auxdisplay: Add 7-segment LED display driver

Add a driver for a 7-segment LED display. At the moment only one
character is supported but it should be possible to expand this to
support more characters and/or 14-segment displays in the future.

Signed-off-by: Chris Packham <chris.packham@alliedtelesis.co.nz>
Reviewed-by: Geert Uytterhoeven <geert@linux-m68k.org>
Signed-off-by: Andy Shevchenko <andriy.shevchenko@linux.intel.com>

drivers/auxdisplay/Kconfig

@@ -211,6 +211,17 @@ config ARM_CHARLCD
 	  line and the Linux version on the second line, but that's
 	  still useful.
 
+config SEG_LED_GPIO
+	tristate "Generic 7-segment LED display"
+	depends on GPIOLIB || COMPILE_TEST
+	select LINEDISP
+	help
+	  This driver supports a generic 7-segment LED display made up
+	  of GPIO pins connected to the individual segments.
+
+	  This driver can also be built as a module. If so, the module
+	  will be called seg-led-gpio.
+
 menuconfig PARPORT_PANEL
 	tristate "Parallel port LCD/Keypad Panel support"
 	depends on PARPORT

drivers/auxdisplay/Makefile

@@ -15,3 +15,4 @@ obj-$(CONFIG_PARPORT_PANEL)	+= panel.o
 obj-$(CONFIG_LCD2S)		+= lcd2s.o
 obj-$(CONFIG_LINEDISP)		+= line-display.o
 obj-$(CONFIG_MAX6959)		+= max6959.o
+obj-$(CONFIG_SEG_LED_GPIO)	+= seg-led-gpio.o

drivers/auxdisplay/seg-led-gpio.c

@@ -0,0 +1,112 @@
+// SPDX-License-Identifier: GPL-2.0
+/*
+ * Driver for a 7-segment LED display
+ *
+ * The decimal point LED present on some devices is currently not
+ * supported.
+ *
+ * Copyright (C) Allied Telesis Labs
+ */
+
+#include <linux/bitmap.h>
+#include <linux/container_of.h>
+#include <linux/errno.h>
+#include <linux/gpio/consumer.h>
+#include <linux/map_to_7segment.h>
+#include <linux/mod_devicetable.h>
+#include <linux/module.h>
+#include <linux/platform_device.h>
+#include <linux/types.h>
+#include <linux/workqueue.h>
+
+#include "line-display.h"
+
+struct seg_led_priv {
+	struct linedisp linedisp;
+	struct delayed_work work;
+	struct gpio_descs *segment_gpios;
+};
+
+static void seg_led_update(struct work_struct *work)
+{
+	struct seg_led_priv *priv = container_of(work, struct seg_led_priv, work.work);
+	struct linedisp *linedisp = &priv->linedisp;
+	struct linedisp_map *map = linedisp->map;
+	DECLARE_BITMAP(values, 8) = { };
+
+	bitmap_set_value8(values, map_to_seg7(&map->map.seg7, linedisp->buf[0]), 0);
+
+	gpiod_set_array_value_cansleep(priv->segment_gpios->ndescs, priv->segment_gpios->desc,
+				       priv->segment_gpios->info, values);
+}
+
+static int seg_led_linedisp_get_map_type(struct linedisp *linedisp)
+{
+	struct seg_led_priv *priv = container_of(linedisp, struct seg_led_priv, linedisp);
+
+	INIT_DELAYED_WORK(&priv->work, seg_led_update);
+	return LINEDISP_MAP_SEG7;
+}
+
+static void seg_led_linedisp_update(struct linedisp *linedisp)
+{
+	struct seg_led_priv *priv = container_of(linedisp, struct seg_led_priv, linedisp);
+
+	schedule_delayed_work(&priv->work, 0);
+}
+
+static const struct linedisp_ops seg_led_linedisp_ops = {
+	.get_map_type = seg_led_linedisp_get_map_type,
+	.update = seg_led_linedisp_update,
+};
+
+static int seg_led_probe(struct platform_device *pdev)
+{
+	struct seg_led_priv *priv;
+	struct device *dev = &pdev->dev;
+
+	priv = devm_kzalloc(dev, sizeof(*priv), GFP_KERNEL);
+	if (!priv)
+		return -ENOMEM;
+
+	platform_set_drvdata(pdev, priv);
+
+	priv->segment_gpios = devm_gpiod_get_array(dev, "segment", GPIOD_OUT_LOW);
+	if (IS_ERR(priv->segment_gpios))
+		return PTR_ERR(priv->segment_gpios);
+
+	if (priv->segment_gpios->ndescs < 7 || priv->segment_gpios->ndescs > 8)
+		return -EINVAL;
+
+	return linedisp_register(&priv->linedisp, dev, 1, &seg_led_linedisp_ops);
+}
+
+static int seg_led_remove(struct platform_device *pdev)
+{
+	struct seg_led_priv *priv = platform_get_drvdata(pdev);
+
+	cancel_delayed_work_sync(&priv->work);
+	linedisp_unregister(&priv->linedisp);
+
+	return 0;
+}
+
+static const struct of_device_id seg_led_of_match[] = {
+	{ .compatible = "gpio-7-segment"},
+	{}
+};
+MODULE_DEVICE_TABLE(of, seg_led_of_match);
+
+static struct platform_driver seg_led_driver = {
+	.probe = seg_led_probe,
+	.remove = seg_led_remove,
+	.driver = {
+		.name = "seg-led-gpio",
+		.of_match_table = seg_led_of_match,
+	},
+};
+module_platform_driver(seg_led_driver);
+
+MODULE_AUTHOR("Chris Packham <chris.packham@alliedtelesis.co.nz>");
+MODULE_DESCRIPTION("7 segment LED driver");
+MODULE_LICENSE("GPL");