leds: trigger: Introduce a MTD (NAND/NOR) trigger

This commit introduces a MTD trigger for flash (NAND/NOR) device
activity. The implementation is copied from IDE disk.

This trigger deprecates the "nand-disk" LED trigger, but for backwards
compatibility, we still keep the "nand-disk" trigger around.

The motivation for deprecating the "nand-disk" LED trigger is that
it only works for NAND drivers, whereas the "mtd" LED trigger
is more generic (in fact, "nand-disk" currently only works for
certain NAND drivers).

Signed-off-by: Ezequiel Garcia <[e-mail]>
Acked-by: Boris Brezillon <[e-mail]>
Signed-off-by: Jacek Anaszewski <[e-mail]>

drivers/leds/trigger/Kconfig

···
 	  This allows LEDs to be controlled by IDE disk activity.
 	  If unsure, say Y.
 
+config LEDS_TRIGGER_MTD
+	bool "LED MTD (NAND/NOR) Trigger"
+	depends on MTD
+	depends on LEDS_TRIGGERS
+	help
+	  This allows LEDs to be controlled by MTD activity.
+	  If unsure, say N.
+
 config LEDS_TRIGGER_HEARTBEAT
 	tristate "LED Heartbeat Trigger"
 	depends on LEDS_TRIGGERS

drivers/leds/trigger/Makefile

···
 obj-$(CONFIG_LEDS_TRIGGER_TIMER)	+= ledtrig-timer.o
 obj-$(CONFIG_LEDS_TRIGGER_ONESHOT)	+= ledtrig-oneshot.o
 obj-$(CONFIG_LEDS_TRIGGER_IDE_DISK)	+= ledtrig-ide-disk.o
+obj-$(CONFIG_LEDS_TRIGGER_MTD)		+= ledtrig-mtd.o
 obj-$(CONFIG_LEDS_TRIGGER_HEARTBEAT)	+= ledtrig-heartbeat.o
 obj-$(CONFIG_LEDS_TRIGGER_BACKLIGHT)	+= ledtrig-backlight.o
 obj-$(CONFIG_LEDS_TRIGGER_GPIO)		+= ledtrig-gpio.o

drivers/leds/trigger/ledtrig-mtd.c

···
+/*
+ * LED MTD trigger
+ *
+ * Copyright 2016 Ezequiel Garcia <[e-mail]>
+ *
+ * Based on LED IDE-Disk Activity Trigger
+ *
+ * Copyright 2006 Openedhand Ltd.
+ *
+ * Author: Richard Purdie <[e-mail]>
+ *
+ * This program is free software; you can redistribute it and/or modify
+ * it under the terms of the GNU General Public License version 2 as
+ * published by the Free Software Foundation.
+ *
+ */
+
+#include <linux/kernel.h>
+#include <linux/init.h>
+#include <linux/leds.h>
+
+#define BLINK_DELAY 30
+
+DEFINE_LED_TRIGGER(ledtrig_mtd);
+DEFINE_LED_TRIGGER(ledtrig_nand);
+
+void ledtrig_mtd_activity(void)
+{
+	unsigned long blink_delay = BLINK_DELAY;
+
+	led_trigger_blink_oneshot(ledtrig_mtd,
+				  &blink_delay, &blink_delay, 0);
+	led_trigger_blink_oneshot(ledtrig_nand,
+				  &blink_delay, &blink_delay, 0);
+}
+EXPORT_SYMBOL(ledtrig_mtd_activity);
+
+static int __init ledtrig_mtd_init(void)
+{
+	led_trigger_register_simple("mtd", &ledtrig_mtd);
+	led_trigger_register_simple("nand-disk", &ledtrig_nand);
+
+	return 0;
+}
+device_initcall(ledtrig_mtd_init);

include/linux/leds.h

···
 static inline void ledtrig_ide_activity(void) {}
 #endif
 
+#ifdef CONFIG_LEDS_TRIGGER_MTD
+extern void ledtrig_mtd_activity(void);
+#else
+static inline void ledtrig_mtd_activity(void) {}
+#endif
+
 #if defined(CONFIG_LEDS_TRIGGER_CAMERA) || defined(CONFIG_LEDS_TRIGGER_CAMERA_MODULE)
 extern void ledtrig_flash_ctrl(bool on);
 extern void ledtrig_torch_ctrl(bool on);