[PATCH] leds: trigger: Introduce an USB port trigger

["Rafał Miłecki" <zajec5@gmail.com>]

This commit adds a new trigger that can turn on LED when USB device gets
connected to the USB port. This can can useful for various home routers
that have USB port and a proper LED telling user a device is connected.

The trigger gets its documentation file but basically it just requires
specifying USB port in a Linux format (e.g. echo 1-1 > new_port).

Signed-off-by: Rafał Miłecki <zajec5@gmail.com>
---
 Documentation/leds/ledtrig-usbport.txt |  47 ++++++++
 drivers/leds/trigger/Kconfig           |   8 ++
 drivers/leds/trigger/Makefile          |   1 +
 drivers/leds/trigger/ledtrig-usbport.c | 196 +++++++++++++++++++++++++++++++++
 4 files changed, 252 insertions(+)
 create mode 100644 Documentation/leds/ledtrig-usbport.txt
 create mode 100644 drivers/leds/trigger/ledtrig-usbport.c

diff --git a/Documentation/leds/ledtrig-usbport.txt b/Documentation/leds/ledtrig-usbport.txt
new file mode 100644
index 0000000..d31dba2
--- /dev/null
+++ b/Documentation/leds/ledtrig-usbport.txt
@@ -0,0 +1,47 @@
+USB port LED trigger
+====================
+
+This LED trigger can be used for signaling user a presence of USB device in a
+given port. It simply turns on LED when device appears and turns it off when it
+disappears.
+
+It requires specifying a list of USB ports that should be observed. Used format
+matches Linux kernel format and consists of a root hub number and a hub port
+separated by a dash (e.g. 3-1).
+
+This also allows handling devices with internal hubs (when root hub's port has
+always a device (hub) connected). User can simply specify specify internal hub
+ports then (e.g. 1-1.1, 1-1.2, etc.).
+
+Please note that this trigger allows assigning multiple USB ports to a single
+LED. This can be useful in two cases:
+
+1) Device with single USB LED and few physical ports
+
+In such case LED will be turned on as long as there is at least one connected
+USB device.
+
+2) Device with a physical port handled by few controllers
+
+Some devices have e.g. one controller per PHY standard. E.g. USB 2.0 physical
+port may be handled by ohci-platform, ehci-platform and xhci-hcd. If there is
+only one LED user will most likely want to assign ports from all 3 hubs.
+
+
+This trigger can be activated from user space on led class devices as shown
+below:
+
+  echo usbport > trigger
+
+This adds the following sysfs attributes to the LED:
+
+  ports - allows listing all USB ports assigned to the trigger.
+
+  new_port - allows adding a new USB port by simply writing to it.
+
+Example use-case:
+
+  echo usbport > trigger
+  echo 4-1 > new_port
+  echo 2-1 > new_port
+  cat ports
diff --git a/drivers/leds/trigger/Kconfig b/drivers/leds/trigger/Kconfig
index 3f9ddb9..bdd6fd2 100644
--- a/drivers/leds/trigger/Kconfig
+++ b/drivers/leds/trigger/Kconfig
@@ -126,4 +126,12 @@ config LEDS_TRIGGER_PANIC
 	  a different trigger.
 	  If unsure, say Y.
 
+config LEDS_TRIGGER_USBPORT
+	tristate "USB port LED trigger"
+	depends on LEDS_TRIGGERS && USB
+	help
+	  This allows LEDs to be controlled by USB events. Enabling this option
+	  allows specifying list of USB ports that should turn on LED when some
+	  USB device gets connected.
+
 endif # LEDS_TRIGGERS
diff --git a/drivers/leds/trigger/Makefile b/drivers/leds/trigger/Makefile
index a72c43c..56e1741 100644
--- a/drivers/leds/trigger/Makefile
+++ b/drivers/leds/trigger/Makefile
@@ -10,3 +10,4 @@ obj-$(CONFIG_LEDS_TRIGGER_DEFAULT_ON)	+= ledtrig-default-on.o
 obj-$(CONFIG_LEDS_TRIGGER_TRANSIENT)	+= ledtrig-transient.o
 obj-$(CONFIG_LEDS_TRIGGER_CAMERA)	+= ledtrig-camera.o
 obj-$(CONFIG_LEDS_TRIGGER_PANIC)	+= ledtrig-panic.o
+obj-$(CONFIG_LEDS_TRIGGER_USBPORT)	+= ledtrig-usbport.o
diff --git a/drivers/leds/trigger/ledtrig-usbport.c b/drivers/leds/trigger/ledtrig-usbport.c
new file mode 100644
index 0000000..eb20a8f
--- /dev/null
+++ b/drivers/leds/trigger/ledtrig-usbport.c
@@ -0,0 +1,196 @@
+/*
+ * USB port LED trigger
+ *
+ * Copyright (C) 2016 Rafał Miłecki <rafal.milecki@gmail.com>
+ *
+ * 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.
+ */
+
+#include <linux/device.h>
+#include <linux/leds.h>
+#include <linux/module.h>
+#include <linux/slab.h>
+#include <linux/usb.h>
+#include "../leds.h"
+
+struct usbport_trig_port {
+	char *name;
+	struct list_head list;
+};
+
+struct usbport_trig_data {
+	struct led_classdev *led_cdev;
+	struct list_head ports;
+	struct notifier_block nb;
+	int count; /* Amount of connected matching devices */
+};
+
+static ssize_t ports_show(struct device *dev, struct device_attribute *attr,
+			  char *buf)
+{
+	struct led_classdev *led_cdev = dev_get_drvdata(dev);
+	struct usbport_trig_data *usbport_data = led_cdev->trigger_data;
+	struct usbport_trig_port *port;
+	ssize_t ret = 0;
+	int len;
+
+	list_for_each_entry(port, &usbport_data->ports, list) {
+		len = sprintf(buf + ret, "%s\n", port->name);
+		if (len >= 0)
+			ret += len;
+	}
+
+	return ret;
+}
+
+static DEVICE_ATTR(ports, S_IRUSR, ports_show, NULL);
+
+static ssize_t new_port_store(struct device *dev, struct device_attribute *attr,
+			      const char *buf, size_t size)
+{
+	struct led_classdev *led_cdev = dev_get_drvdata(dev);
+	struct usbport_trig_data *usbport_data = led_cdev->trigger_data;
+	struct usbport_trig_port *port;
+	size_t len;
+
+	port = kzalloc(sizeof(*port), GFP_KERNEL);
+	if (!port)
+		return -ENOMEM;
+
+	len = strlen(buf);
+	if (len && buf[len - 1] == '\n')
+		len--;
+	if (!len)
+		return -EINVAL;
+
+	port->name = kzalloc(strlen(buf), GFP_KERNEL);
+	if (!port->name) {
+		kfree(port);
+		return -ENOMEM;
+	}
+	strncpy(port->name, buf, len);
+
+	list_add_tail(&port->list, &usbport_data->ports);
+
+	return size;
+}
+
+static DEVICE_ATTR(new_port, S_IWUSR, NULL, new_port_store);
+
+static bool usbport_trig_match(struct usbport_trig_data *usbport_data,
+			       struct usb_device *usb_dev)
+{
+	struct usbport_trig_port *port;
+	const char *name = dev_name(&usb_dev->dev);
+
+	list_for_each_entry(port, &usbport_data->ports, list) {
+		if (!strcmp(port->name, name))
+			return true;
+	}
+
+	return false;
+}
+
+static int usbport_trig_notify(struct notifier_block *nb, unsigned long action,
+			       void *data)
+{
+	struct usbport_trig_data *usbport_data =
+		container_of(nb, struct usbport_trig_data, nb);
+	struct led_classdev *led_cdev = usbport_data->led_cdev;
+
+	switch (action) {
+	case USB_DEVICE_ADD:
+		if (usbport_trig_match(usbport_data, data)) {
+			if (usbport_data->count++ == 0)
+				led_set_brightness_nosleep(led_cdev, LED_FULL);
+		}
+		break;
+	case USB_DEVICE_REMOVE:
+		if (usbport_trig_match(usbport_data, data)) {
+			if (--usbport_data->count == 0)
+				led_set_brightness_nosleep(led_cdev, LED_OFF);
+		}
+		break;
+	}
+
+	return NOTIFY_OK;
+}
+
+static void usbport_trig_activate(struct led_classdev *led_cdev)
+{
+	struct usbport_trig_data *usbport_data;
+	int err;
+
+	usbport_data = kzalloc(sizeof(*usbport_data), GFP_KERNEL);
+	if (!usbport_data)
+		return;
+	usbport_data->led_cdev = led_cdev;
+	INIT_LIST_HEAD(&usbport_data->ports);
+	usbport_data->nb.notifier_call = usbport_trig_notify,
+	led_cdev->trigger_data = usbport_data;
+
+	err = device_create_file(led_cdev->dev, &dev_attr_ports);
+	if (err)
+		goto err_free;
+	err = device_create_file(led_cdev->dev, &dev_attr_new_port);
+	if (err)
+		goto err_remove_ports;
+
+	usb_register_notify(&usbport_data->nb);
+
+	led_cdev->activated = true;
+	return;
+
+err_free:
+	kfree(usbport_data);
+err_remove_ports:
+	device_remove_file(led_cdev->dev, &dev_attr_ports);
+}
+
+static void usbport_trig_deactivate(struct led_classdev *led_cdev)
+{
+	struct usbport_trig_data *usbport_data = led_cdev->trigger_data;
+	struct usbport_trig_port *port, *tmp;
+
+	if (!led_cdev->activated)
+		return;
+
+	usb_unregister_notify(&usbport_data->nb);
+
+	list_for_each_entry_safe(port, tmp, &usbport_data->ports, list) {
+		kfree(port->name);
+		list_del(&port->list);
+	}
+
+	device_remove_file(led_cdev->dev, &dev_attr_new_port);
+	device_remove_file(led_cdev->dev, &dev_attr_ports);
+	kfree(usbport_data);
+
+	led_cdev->activated = false;
+}
+
+static struct led_trigger usbport_led_trigger = {
+	.name     = "usbport",
+	.activate = usbport_trig_activate,
+	.deactivate = usbport_trig_deactivate,
+};
+
+static int __init usbport_trig_init(void)
+{
+	return led_trigger_register(&usbport_led_trigger);
+}
+
+static void __exit usbport_trig_exit(void)
+{
+	led_trigger_unregister(&usbport_led_trigger);
+}
+
+module_init(usbport_trig_init);
+module_exit(usbport_trig_exit);
+
+MODULE_AUTHOR("Rafał Miłecki <rafal.milecki@gmail.com>");
+MODULE_DESCRIPTION("USB port trigger");
+MODULE_LICENSE("GPL");
-- 
1.8.4.5