[PATCH v2 1/4] auxdisplay: Add 7 segment LED display driver

Chris Packham
2024-02-27T21:22:48Z

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>
---

Notes:
Changes in v2:
- Rebased on top of auxdisplay/for-next dropping unnecessary code for 7
segment maps.
- Update for new linedisp_register() API
- Include headers based on actual usage
- Allow building as module
- Use compatible = "generic-gpio-7seg" to keep checkpatch.pl happy

drivers/auxdisplay/Kconfig | 10 +++
drivers/auxdisplay/Makefile | 1 +
drivers/auxdisplay/seg-led.c | 119 +++++++++++++++++++++++++++++++++++
3 files changed, 130 insertions(+)
create mode 100644 drivers/auxdisplay/seg-led.c

diff --git a/drivers/auxdisplay/Kconfig b/drivers/auxdisplay/Kconfig
index d4be0a3695ce..52a245ca0c8d 100644
--- a/drivers/auxdisplay/Kconfig
+++ b/drivers/auxdisplay/Kconfig
@@ -211,6 +211,16 @@ config ARM_CHARLCD
line and the Linux version on the second line, but that's
still useful.

+config SEG_LED
+ tristate "Generic 7 segment LED display"
+ 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.
+
menuconfig PARPORT_PANEL
tristate "Parallel port LCD/Keypad Panel support"
depends on PARPORT
diff --git a/drivers/auxdisplay/Makefile b/drivers/auxdisplay/Makefile
index a725010ca651..744e354318ae 100644
--- a/drivers/auxdisplay/Makefile
+++ b/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) += seg-led.o
diff --git a/drivers/auxdisplay/seg-led.c b/drivers/auxdisplay/seg-led.c
new file mode 100644
index 000000000000..7bb304fcaa6e
--- /dev/null
+++ b/drivers/auxdisplay/seg-led.c
@@ -0,0 +1,119 @@
+// SPDX-License-Identifier: GPL-2.0
+/*
+ * Driver for a 7 segment LED display
+ *
+ * The GPIOs are wired to the 7 segments in a clockwise fashion starting from
+ * the top.
+ *
+ * -a-
+ * | |
+ * f b
+ * | |
+ * -g-
+ * | |
+ * e c
+ * | |
+ * -d-
+ *
+ * The decimal point LED present on some devices is currently not
+ * supported.
+ *
+ * Copyright (C) Allied Telesis Labs
+ */
+
+#include <linux/container_of.h>
+#include <linux/errno.h>
+#include <linux/gpio/consumer.h>
+#include <linux/kernel.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 gpio_descs *segment_gpios;
+ struct delayed_work work;
+ struct linedisp linedisp;
+};
+
+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_map *map = priv->linedisp.map;
+ DECLARE_BITMAP(values, 8);
+
+ values[0] = map_to_seg7(&map->map.seg7, priv->linedisp.buf[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)
+{
+ 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 const struct of_device_id seg_led_of_match[] = {
+ { .compatible = "generic-gpio-7seg"},
+ {}
+};
+MODULE_DEVICE_TABLE(of, seg_led_of_match);
+
+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);
+
+ INIT_DELAYED_WORK(&priv->work, seg_led_update);
+
+ 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 struct platform_driver seg_led_driver = {
+ .probe = seg_led_probe,
+ .remove = seg_led_remove,
+ .driver = {
+ .name = "seg-led",
+ .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");
--
2.43.2