linux: up-kbd-backlight-led: the keyboard backlight control implementation for Linux

The implementation for Linux included:
1. Set and get brightness.
2. Get max brightness.
3. Signal if the brightness was changed by the device.

3 files changed, 380 insertions, 0 deletions

diff --git a/src/linux/meson.build b/src/linux/meson.build
index 1134e7c..55fee12 100644
--- a/src/linux/meson.build
+++ b/src/linux/meson.build
@@ -18,6 +18,8 @@ upshared += { 'linux': static_library('upshared',
         'up-device-wup.h',
         'up-device-bluez.c',
         'up-device-bluez.h',
+        'up-kbd-backlight-led.c',
+        'up-kbd-backlight-led.h',
         'up-input.c',
         'up-input.h',
         'up-backend.c',
diff --git a/src/linux/up-kbd-backlight-led.c b/src/linux/up-kbd-backlight-led.c
new file mode 100644
index 0000000..3981198
--- /dev/null
+++ b/src/linux/up-kbd-backlight-led.c
@@ -0,0 +1,323 @@
+/* -*- Mode: C; tab-width: 8; indent-tabs-mode: t; c-basic-offset: 8 -*-
+ *
+ * Copyright (C) 2025 Kate Hsuan <p.hsuan@gmail.com>
+ *
+ * Licensed under the GNU General Public License Version 2
+ *
+ * This program is free software; you can redistribute it and/or modify
+ * it under the terms of the GNU General Public License as published by
+ * the Free Software Foundation; either version 2 of the License, or
+ * (at your option) any later version.
+ *
+ * This program is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+ * GNU General Public License for more details.
+ *
+ * You should have received a copy of the GNU General Public License
+ * along with this program; if not, write to the Free Software
+ * Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA.
+ */
+
+#include "config.h"
+
+#include <glib.h>
+#include <glib/gi18n.h>
+#include <sys/types.h>
+#include <sys/stat.h>
+#include <fcntl.h>
+#include <unistd.h>
+#include <string.h>
+#include <dirent.h>
+#include <errno.h>
+
+#include "up-kbd-backlight-led.h"
+#include "up-native.h"
+#include "up-types.h"
+
+static void     up_kbd_backlight_led_finalize   (GObject	*object);
+
+struct UpKbdBacklightLedPrivate
+{
+	gint			 max_brightness;
+	guint			 brightness;
+
+	gint			 fd_hw_changed;
+	GIOChannel		*channel_hw_changed;
+};
+
+G_DEFINE_TYPE_WITH_PRIVATE (UpKbdBacklightLed, up_kbd_backlight_led, UP_TYPE_DEVICE_KBD_BACKLIGHT)
+
+
+/**
+ * up_kbd_backlight_led_brightness_write:
+ *
+ * Write the brightness value to the LED device with a given path.
+ **/
+static gboolean
+up_kbd_backlight_led_brightness_write (UpDeviceKbdBacklight *kbd_backlight, const gchar *native_path, gint value)
+{
+	UpKbdBacklightLed *kbd;
+	UpKbdBacklightLedPrivate *priv;
+	g_autoptr (GString) value_str = g_string_new (NULL);
+
+	g_return_val_if_fail (UP_IS_DEVICE_KBD_BACKLIGHT (kbd_backlight), FALSE);
+
+	kbd = UP_KBD_BACKLIGHT_LED (kbd_backlight);
+	priv = up_kbd_backlight_led_get_instance_private (kbd);
+
+	g_string_printf (value_str, "%d", CLAMP (value, 0, priv->max_brightness));
+	if (!g_file_set_contents_full (native_path, value_str->str, value_str->len,
+				       G_FILE_SET_CONTENTS_ONLY_EXISTING, 0644, NULL)) {
+		g_debug ("Failed on setting keyboard backlight LED brightness: %s", native_path);
+		return FALSE;
+	}
+
+	return TRUE;
+}
+
+/**
+ * up_kbd_backlight_led_brightness_read:
+ *
+ * Read the brightness value from the LED device with a given path.
+ **/
+static gint
+up_kbd_backlight_led_brightness_read (UpDeviceKbdBacklight *kbd_backlight, const gchar *native_path)
+{
+	g_autofree gchar *buf = NULL;
+	gint64 brightness = -1;
+
+	g_return_val_if_fail (UP_IS_DEVICE_KBD_BACKLIGHT (kbd_backlight), brightness);
+
+	if (!g_file_get_contents (native_path, &buf, NULL, NULL))
+		return -1;
+
+	g_strstrip (buf);
+	g_debug ("brightness: %s", buf);
+
+	brightness = g_ascii_strtoll (buf, NULL, 10);
+	if (brightness < 0) {
+		g_warning ("failed to convert brightness.");
+		return -1;
+	}
+
+	return brightness;
+}
+
+/**
+ * up_kbd_backlight_led_set_brightness:
+ *
+ * Set the brightness.
+ **/
+static gboolean
+up_kbd_backlight_led_set_brightness (UpDeviceKbdBacklight *kbd_backlight, gint value)
+{
+	GObject *native;
+	g_autofree gchar *filename = NULL;
+	const gchar *native_path;
+	gboolean ret = FALSE;
+
+	native = up_device_kbd_backlight_get_native (UP_DEVICE_KBD_BACKLIGHT (kbd_backlight));
+	g_return_val_if_fail (native != NULL, FALSE);
+
+	native_path = up_native_get_native_path (native);
+	g_return_val_if_fail (native_path != NULL, FALSE);
+
+	filename = g_build_filename (native_path, "brightness", NULL);
+
+	ret = up_kbd_backlight_led_brightness_write (kbd_backlight, filename, value);
+
+	return ret;
+}
+
+/**
+ * up_kbd_backlight_led_get_brightness:
+ *
+ * Get the brightness.
+ **/
+static gint
+up_kbd_backlight_led_get_brightness (UpDeviceKbdBacklight *kbd_backlight)
+{
+	GObject *native;
+	const gchar *native_path;
+	g_autofree gchar *filename = NULL;
+	gint brightness = -1;
+
+	native = up_device_kbd_backlight_get_native (UP_DEVICE_KBD_BACKLIGHT (kbd_backlight));
+	g_return_val_if_fail (native != NULL, brightness);
+
+	native_path = up_native_get_native_path (native);
+	g_return_val_if_fail (native_path != NULL, brightness);
+
+	filename = g_build_filename (native_path, "brightness", NULL);
+	brightness = up_kbd_backlight_led_brightness_read (kbd_backlight, filename);
+
+	return brightness;
+}
+
+/**
+ * up_kbd_backlight_led_get_max_brightness:
+ *
+ * Gets the max brightness.
+ **/
+static gint
+up_kbd_backlight_led_get_max_brightness (UpDeviceKbdBacklight *kbd_backlight)
+{
+	UpKbdBacklightLed *kbd = UP_KBD_BACKLIGHT_LED (kbd_backlight);
+	UpKbdBacklightLedPrivate *priv = up_kbd_backlight_led_get_instance_private (kbd);
+	return priv->max_brightness;
+}
+
+/**
+ * up_kbd_backlight_led_event_io:
+ *
+ * This function is called when the brightness of the LED device changes.
+ **/
+static gboolean
+up_kbd_backlight_led_event_io (GIOChannel *channel, GIOCondition condition, gpointer data)
+{
+	UpDeviceKbdBacklight *kbd_backlight = UP_DEVICE_KBD_BACKLIGHT (data);
+	UpKbdBacklightLed *kbd = UP_KBD_BACKLIGHT_LED (kbd_backlight);
+	UpKbdBacklightLedPrivate *priv = up_kbd_backlight_led_get_instance_private (kbd);
+	gint brightness = 0;
+	gchar buf[16];
+	g_autofree gchar *ret_str = NULL;
+	glong len;
+	gchar *end = NULL;
+
+	if (priv->fd_hw_changed < 0)
+		return FALSE;
+
+	if (!(condition & G_IO_PRI))
+		return FALSE;
+
+	lseek (priv->fd_hw_changed, 0, SEEK_SET);
+	len = read (priv->fd_hw_changed, buf, G_N_ELEMENTS (buf) - 1);
+
+	if (len > 0) {
+		buf[len] = '\0';
+		g_strstrip (buf);
+		brightness = g_ascii_strtoll (buf, &end, 10);
+
+		if (brightness < 0 ||
+		    brightness > priv->max_brightness ||
+		    end == buf) {
+			brightness = -1;
+			g_warning ("kbd eventio: failed to convert brightness.");
+		}
+	}
+	g_debug ("kbd eventio: brightness: %d", brightness);
+
+	if (brightness < 0)
+		return FALSE;
+
+	if (brightness >= 0)
+		up_device_kbd_backlight_emit_change (kbd_backlight, brightness, "internal");
+
+	return TRUE;
+}
+
+/**
+ * up_kbd_backlight_led_coldplug:
+ *
+ * Update the LED settings to UpKbdBacklightLed device.
+ **/
+static gboolean
+up_kbd_backlight_led_coldplug (UpDeviceKbdBacklight *kbd_backlight)
+{
+	UpKbdBacklightLed *kbd;
+	UpKbdBacklightLedPrivate *priv;
+	GObject *native;
+	g_autofree gchar *filename = NULL;
+	g_autofree gchar *path_hw_changed = NULL;
+	const gchar *native_path = NULL;
+
+	g_return_val_if_fail (UP_IS_DEVICE_KBD_BACKLIGHT (kbd_backlight), FALSE);
+
+	kbd = UP_KBD_BACKLIGHT_LED (kbd_backlight);
+	priv = up_kbd_backlight_led_get_instance_private (kbd);
+
+	native = up_device_kbd_backlight_get_native (kbd_backlight);
+	if (native == NULL) {
+		priv->max_brightness = 0;
+		return FALSE;
+	}
+
+	native_path = up_native_get_native_path (native);
+	filename = g_build_filename (native_path, "max_brightness", NULL);
+
+	priv->max_brightness = up_kbd_backlight_led_brightness_read (kbd_backlight, filename);
+
+	/* Set up device watcher */
+	path_hw_changed = g_build_filename (native_path, "brightness_hw_changed", NULL);
+	priv->fd_hw_changed = open (path_hw_changed, O_RDONLY);
+	if (priv->fd_hw_changed >= 0) {
+		priv->channel_hw_changed = g_io_channel_unix_new (priv->fd_hw_changed);
+		g_io_add_watch (priv->channel_hw_changed,
+				G_IO_PRI, up_kbd_backlight_led_event_io, kbd_backlight);
+	}
+
+	return TRUE;
+}
+
+
+/**
+ * up_kbd_backlight_led_finalize:
+ **/
+static void
+up_kbd_backlight_led_finalize (GObject *object)
+{
+	UpKbdBacklightLed *kbd_backlight;
+	UpKbdBacklightLedPrivate *priv;
+
+	g_return_if_fail (object != NULL);
+	g_return_if_fail (UP_IS_KBD_BACKLIGHT_LED (object));
+
+	kbd_backlight = UP_KBD_BACKLIGHT_LED (object);
+	priv = up_kbd_backlight_led_get_instance_private (kbd_backlight);
+
+	if (priv->channel_hw_changed) {
+		g_io_channel_shutdown (priv->channel_hw_changed, FALSE, NULL);
+		g_io_channel_unref (priv->channel_hw_changed);
+	}
+
+	if (priv->fd_hw_changed >= 0)
+		close (priv->fd_hw_changed);
+
+	G_OBJECT_CLASS (up_kbd_backlight_led_parent_class)->finalize (object);
+}
+
+/**
+ * up_kbd_backlight_led_class_init:
+ **/
+static void
+up_kbd_backlight_led_class_init (UpKbdBacklightLedClass *klass)
+{
+	GObjectClass *object_class = G_OBJECT_CLASS (klass);
+	UpDeviceKbdBacklightClass *dev_kbd_klass = UP_DEVICE_KBD_BACKLIGHT_CLASS (klass);
+
+	object_class->finalize = up_kbd_backlight_led_finalize;
+
+	dev_kbd_klass->coldplug = up_kbd_backlight_led_coldplug;
+	dev_kbd_klass->get_max_brightness = up_kbd_backlight_led_get_max_brightness;
+	dev_kbd_klass->get_brightness = up_kbd_backlight_led_get_brightness;
+	dev_kbd_klass->set_brightness = up_kbd_backlight_led_set_brightness;
+}
+
+/**
+ * up_kbd_backlight_led_init:
+ **/
+static void
+up_kbd_backlight_led_init (UpKbdBacklightLed *kbd_backlight)
+{
+	kbd_backlight->priv = up_kbd_backlight_led_get_instance_private (kbd_backlight);
+}
+
+/**
+ * up_kbd_backlight_led_new:
+ **/
+UpKbdBacklightLed *
+up_kbd_backlight_led_new (void)
+{
+	return g_object_new (UP_TYPE_KBD_BACKLIGHT_LED, NULL);
+}
diff --git a/src/linux/up-kbd-backlight-led.h b/src/linux/up-kbd-backlight-led.h
new file mode 100644
index 0000000..101fe1d
--- /dev/null
+++ b/src/linux/up-kbd-backlight-led.h
@@ -0,0 +1,55 @@
+/* -*- Mode: C; tab-width: 8; indent-tabs-mode: t; c-basic-offset: 8 -*-
+ *
+ * Copyright (C) 2025 Kate Hsuan <p.hsuan@gmail.com>
+ *
+ * Licensed under the GNU General Public License Version 2
+ *
+ * This program is free software; you can redistribute it and/or modify
+ * it under the terms of the GNU General Public License as published by
+ * the Free Software Foundation; either version 2 of the License, or
+ * (at your option) any later version.
+ *
+ * This program is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+ * GNU General Public License for more details.
+ *
+ * You should have received a copy of the GNU General Public License
+ * along with this program; if not, write to the Free Software
+ * Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA.
+ */
+
+#ifndef __UP_KBD_BACKLIGHT_LED_H
+#define __UP_KBD_BACKLIGHT_LED_H
+
+#include <glib-object.h>
+#include "up-device-kbd-backlight.h"
+
+G_BEGIN_DECLS
+
+#define UP_TYPE_KBD_BACKLIGHT_LED		(up_kbd_backlight_led_get_type ())
+#define UP_KBD_BACKLIGHT_LED(o)			(G_TYPE_CHECK_INSTANCE_CAST ((o), UP_TYPE_KBD_BACKLIGHT_LED, UpKbdBacklightLed))
+#define UP_KBD_BACKLIGHT_LED_CLASS(k)		(G_TYPE_CHECK_CLASS_CAST((k), UP_TYPE_KBD_BACKLIGHT_LED, UpKbdBacklightLedClass))
+#define UP_IS_KBD_BACKLIGHT_LED(o)		(G_TYPE_CHECK_INSTANCE_TYPE ((o), UP_TYPE_KBD_BACKLIGHT_LED))
+#define UP_IS_KBD_BACKLIGHT_LED_CLASS(k)	(G_TYPE_CHECK_CLASS_TYPE ((k), UP_TYPE_KBD_BACKLIGHT_LED))
+#define UP_KBD_BACKLIGHT_LED_GET_CLASS(o)	(G_TYPE_INSTANCE_GET_CLASS ((o), UP_TYPE_KBD_BACKLIGHT_LED, UpKbdBacklightLedClass))
+
+typedef struct UpKbdBacklightLedPrivate UpKbdBacklightLedPrivate;
+
+typedef struct
+{
+	UpDeviceKbdBacklight		 parent;
+	UpKbdBacklightLedPrivate	*priv;
+} UpKbdBacklightLed;
+
+typedef struct
+{
+	UpDeviceKbdBacklightClass		 parent_class;
+} UpKbdBacklightLedClass;
+
+UpKbdBacklightLed	*up_kbd_backlight_led_new			(void);
+GType		 	 up_kbd_backlight_led_get_type			(void);
+
+G_END_DECLS
+
+#endif	/* __UP_KBD_BACKLIGHT_LED_H */