Add "blkdev" LED trigger to blink LEDs in response to block device
activity.
Add LEDS_TRIGGER_BLKDEV (tristate) config option to control building of
the trigger.
Signed-off-by: Ian Pilcher <arequipeno@xxxxxxxxx>
---
drivers/leds/trigger/Kconfig | 9 +
drivers/leds/trigger/Makefile | 1 +
drivers/leds/trigger/ledtrig-blkdev.c | 981 ++++++++++++++++++++++++++
3 files changed, 991 insertions(+)
create mode 100644 drivers/leds/trigger/ledtrig-blkdev.c
diff --git a/drivers/leds/trigger/Kconfig b/drivers/leds/trigger/Kconfig
index 1f1d57288085..219d15c046d7 100644
--- a/drivers/leds/trigger/Kconfig
+++ b/drivers/leds/trigger/Kconfig
@@ -153,4 +153,13 @@ config LEDS_TRIGGER_TTY
When build as a module this driver will be called ledtrig-tty.
+config LEDS_TRIGGER_BLKDEV
+ tristate "LED Trigger for block devices"
+ depends on BLOCK
+ help
+ The blkdev LED trigger allows LEDs to be controlled by block device
+ activity (reads and writes).
+
+ See Documentation/leds/ledtrig-blkdev.rst.
+
endif # LEDS_TRIGGERS
diff --git a/drivers/leds/trigger/Makefile b/drivers/leds/trigger/Makefile
index 25c4db97cdd4..d53bab5d93f1 100644
--- a/drivers/leds/trigger/Makefile
+++ b/drivers/leds/trigger/Makefile
@@ -16,3 +16,4 @@ obj-$(CONFIG_LEDS_TRIGGER_NETDEV) += ledtrig-netdev.o
obj-$(CONFIG_LEDS_TRIGGER_PATTERN) += ledtrig-pattern.o
obj-$(CONFIG_LEDS_TRIGGER_AUDIO) += ledtrig-audio.o
obj-$(CONFIG_LEDS_TRIGGER_TTY) += ledtrig-tty.o
+obj-$(CONFIG_LEDS_TRIGGER_BLKDEV) += ledtrig-blkdev.o
diff --git a/drivers/leds/trigger/ledtrig-blkdev.c b/drivers/leds/trigger/ledtrig-blkdev.c
new file mode 100644
index 000000000000..8cb0d3b1e7ed
--- /dev/null
+++ b/drivers/leds/trigger/ledtrig-blkdev.c
@@ -0,0 +1,981 @@
+// SPDX-License-Identifier: GPL-2.0-only
+
+/*
+ * Block device LED trigger
+ *
+ * Copyright 2021 Ian Pilcher <arequipeno@xxxxxxxxx>
+ */
+
+#include <linux/blkdev.h>
+#include <linux/leds.h>
+#include <linux/module.h>
+#include <linux/part_stat.h>
+
+/* Default blink time & check interval (milliseconds) */
+#define LED_BDEV_BLINK_MSEC 75
+#define LED_BDEV_INTERVAL 100
+
+/* Minimum blink time & check interval (milliseconds) */
+#define LED_BDEV_MIN_BLINK 10
+#define LED_BDEV_MIN_INT 25
+
+/* Device activity type that will make LED blink */
+enum led_bdev_mode {
+ LED_BDEV_MODE_RO = 0,
+ LED_BDEV_MODE_WO = 1,
+ LED_BDEV_MODE_RW = 2
+};
+
+/* Block device information (BDI) - 1 per blkdev linked to at least 1 LED */
+struct led_bdev_bdi {
+ struct block_device *bdev;
+ struct hlist_head leds;
+ unsigned long read_ios;
+ unsigned long write_ios;
+ unsigned int generation;
+ bool read_act;
+ bool write_act;
+};
+
+/* For many-to-many relationships between block devices and LEDs */
+struct led_bdev_link {
+ struct hlist_node bdi_leds_node;
+ struct hlist_node led_bdis_node;
+ struct led_bdev_bdi *bdi;
+ struct led_bdev_led *led;
+};
+
+/* Every LED associated with the blkdev trigger gets one of these */
+struct led_bdev_led {
+ struct led_classdev *led_cdev;
+ unsigned int blink_msec;
+ struct hlist_head bdis;
+ struct hlist_node leds_node;
+ enum led_bdev_mode mode;
+};
+
+/* Forward declarations to make this file compile in a reasonable order */
+static void led_bdev_process(struct work_struct *work);
+static struct led_bdev_bdi *led_bdev_get_bdi(const char *buf, size_t size);
+static struct block_device *led_bdev_get(const char *buf, size_t size,
+ fmode_t mode);
+static int led_bdev_link(struct led_bdev_led *led, struct led_bdev_bdi *bdi);
+static void led_bdev_put_bdi(struct led_bdev_bdi *bdi);
+static void led_bdev_bdi_release(struct device *dev, void *res);
+static void led_bdev_unlink(struct led_bdev_led *led,
+ struct led_bdev_link *link,
+ struct led_bdev_bdi *bdi, bool releasing);
+static void led_bdev_update_bdi(struct led_bdev_bdi *bdi);
+static bool led_bdev_blink(const struct led_bdev_led *led,
+ const struct led_bdev_bdi *bdi);
+
+/* Protects everything except atomic sysfs attributes */
+static DEFINE_MUTEX(led_bdev_mutex);
+
+/* All LEDs associated with the trigger */
+static HLIST_HEAD(led_bdev_leds);
+
+/* sysfs class for "global" trigger attributes (interval) */
+static struct class *led_bdev_class;
+
+/* Delayed work to periodically check for activity & blink LEDs */
+static DECLARE_DELAYED_WORK(led_bdev_work, led_bdev_process);
+
+/* How often to run the delayed work - in jiffies */
+static unsigned int led_bdev_interval;
+
+/* Incremented every time the delayed work runs */
+static unsigned int led_bdev_generation;
+
+/* Total number of device-to-LED associations (links) */
+static unsigned int led_bdev_link_count;
+
+/* Empty attribute list for the linked_leds & linked_devices "groups" */
+static struct attribute *led_bdev_attrs_empty[] = { NULL };
+
+/* linked_leds sysfs directory for block devs linked to 1 or more LEDs */
+static const struct attribute_group led_bdev_linked_leds = {
+ .name = "linked_leds",
+ .attrs = led_bdev_attrs_empty,
+};
+
+/* linked_devices sysfs directory for each LED associated with the trigger */
+static const struct attribute_group led_bdev_linked_devs = {
+ .name = "linked_devices",
+ .attrs = led_bdev_attrs_empty,
+};
+
+/**
+ * led_bdev_activate() - Called when an LED is associated with the trigger.
+ * @led_cdev: The LED
+ *
+ * Allocates & initializes the @led_bdev_led structure, adds it to the
+ * @led_bdev_leds list, and sets the LED's trigger data.
+ *
+ * Context: Process context. Takes and releases @led_bdev_mutex.
+ * Return: ``0`` on success, ``-errno`` on error.
+ */
+static int led_bdev_activate(struct led_classdev *const led_cdev)
+{
+ struct led_bdev_led *led;
+ int ret;
+
+ led = kmalloc(sizeof(*led), GFP_KERNEL);
+ if (led == NULL) {
+ ret = -ENOMEM;
+ goto exit_return;
+ }
+
+ led->led_cdev = led_cdev;
+ led->blink_msec = LED_BDEV_BLINK_MSEC;
+ led->mode = LED_BDEV_MODE_RW;
+ INIT_HLIST_HEAD(&led->bdis);
+
+ ret = mutex_lock_interruptible(&led_bdev_mutex);
+ if (ret != 0)
+ goto exit_free;
+
+ hlist_add_head(&led->leds_node, &led_bdev_leds);
+ led_set_trigger_data(led_cdev, led);
+
+ mutex_unlock(&led_bdev_mutex);
+
+exit_free:
+ if (ret != 0)
+ kfree(led);
+exit_return:
+ return ret;
+}
+
+/**
+ * link_device_store() - ``link_device`` device attribute store function.
+ * @dev: The LED device
+ * @attr: The ``link_device`` attribute (@dev_attr_link_device)
+ * @buf: The value written to the attribute, which should be the path to
+ * the special file that represents the block device to be linked
+ * to the LED (e.g. /dev/sda)
+ * @count: The number of characters in @buf
+ *
+ * Calls led_bdev_get_bdi() to find or create the BDI for the block device,
+ * checks that the device isn't already linked to this LED, and calls
+ * led_bdev_link() to create the link.
+ *
+ * Context: Process context. Takes and releases @led_bdev_mutex.
+ * Return: @count on success, ``-errno`` on error.
+ */
+static ssize_t link_device_store(struct device *const dev,
+ struct device_attribute *const attr,
+ const char *const buf, const size_t count)
+{
+ struct led_bdev_led *const led = led_trigger_get_drvdata(dev);
+ const struct led_bdev_link *link;
+ struct led_bdev_bdi *bdi;
+ int ret;
+
+ ret = mutex_lock_interruptible(&led_bdev_mutex);
+ if (ret != 0)
+ goto exit_return;
+
+ bdi = led_bdev_get_bdi(buf, count);
+ if (IS_ERR(bdi)) {
+ ret = PTR_ERR(bdi);
+ goto exit_unlock;
+ }
+
+ hlist_for_each_entry (link, &bdi->leds, bdi_leds_node) {
+ if (link->led == led) {
+ ret = -EEXIST;
+ goto exit_put_bdi;
+ }
+ }
+
+ ret = led_bdev_link(led, bdi);
+
+exit_put_bdi:
+ if (ret != 0)
+ led_bdev_put_bdi(bdi);
+exit_unlock:
+ mutex_unlock(&led_bdev_mutex);
+exit_return:
+ return (ret == 0) ? count : ret;
+}
+
+/**
+ * led_bdev_get_bdi() - Find or create the BDI for a block device.
+ * @buf: The value written to the ``link_device`` attribute, which should
+ * be the path to a special file that represents a block device
+ * @count: The number of characters in @buf
+ *
+ * Calls led_bdev_get() to get the block device represented by the path in @buf.
+ * If the device already has a BDI (because it is already linked to an LED),
+ * simply returns the existing BDI.
+ *
+ * Otherwise, allocates a new BDI (as a device resource), creates the block
+ * device's ``linked_leds`` directory (attribute group), calls
+ * led_bdev_update_bdi() to set the BDI's activity counters, and adds the BDI
+ * resource to the block device.
+ *
+ * Context: Process context. Caller must hold @led_bdev_mutex.
+ * Return: Pointer to the BDI, error pointer on error.
+ */
+static struct led_bdev_bdi *led_bdev_get_bdi(const char *const buf,
+ const size_t count)
+{
+ struct block_device *bdev;
+ struct led_bdev_bdi *bdi;
+ struct device *dev;
+ int ret;
+
+ bdev = led_bdev_get(buf, count, 0);
+ if (IS_ERR(bdev)) {
+ ret = PTR_ERR(bdev);
+ goto exit_return;
+ }
+
+ dev = &bdev->bd_device;
+
+ bdi = devres_find(dev, led_bdev_bdi_release, NULL, NULL);
+ if (bdi != NULL) {
+ ret = 0;
+ goto exit_put_bdev;
+ }
+
+ bdi = devres_alloc(led_bdev_bdi_release, sizeof(*bdi), GFP_KERNEL);
+ if (bdi == NULL) {
+ ret = -ENOMEM;
+ goto exit_put_bdev;
+ }
+
+ ret = sysfs_create_group(&dev->kobj, &led_bdev_linked_leds);
+ if (ret != 0)
+ goto exit_free_bdi;
+
+ bdi->bdev = bdev;
+ INIT_HLIST_HEAD(&bdi->leds);
+
+ /* Ensure that led_bdev_update_bdi() updates BDI */
+ bdi->generation = led_bdev_generation - 1;
+ led_bdev_update_bdi(bdi);
+ /* Don't blink for activity that may have happened long ago */
+ bdi->read_act = false;
+ bdi->write_act = false;
+
+ devres_add(dev, bdi);
+
+exit_free_bdi:
+ if (ret != 0)
+ devres_free(bdi);
+exit_put_bdev:
+ blkdev_put(bdev, 0); /* Allow the device to be released */
+exit_return:
+ return (ret == 0) ? bdi : ERR_PTR(ret);
+}
+
+/**
+ * led_bdev_update_bdi() - Update a BDI's activity counters for the current
+ * generation
+ * @bdi: The BDI
+ *
+ * Does nothing if the BDI has already been updated during this generation.
+ *
+ * Otherwise, updates the BDI's activity counters (@read_ios & @write_ios) and
+ * @generation, and sets @read_act and/or @write_act if the corresponding
+ * counters have changed.
+ *
+ * Context: Process context. Caller must hold @led_bdev_mutex.
+ */
+static void led_bdev_update_bdi(struct led_bdev_bdi *const bdi)
+{
+ unsigned long read_ios, write_ios;
+
+ if (bdi->generation != led_bdev_generation) {
+
+ read_ios = part_stat_read(bdi->bdev, ios[STAT_READ]);
+
+ write_ios = part_stat_read(bdi->bdev, ios[STAT_WRITE])
+ + part_stat_read(bdi->bdev, ios[STAT_DISCARD])
+ + part_stat_read(bdi->bdev, ios[STAT_FLUSH]);
+
+ if (bdi->read_ios != read_ios) {
+ bdi->read_act = true;
+ bdi->read_ios = read_ios;
+ } else {
+ bdi->read_act = false;
+ }
+
+ if (bdi->write_ios != write_ios) {
+ bdi->write_act = true;
+ bdi->write_ios = write_ios;
+ } else {
+ bdi->write_act = false;
+ }
+
+ bdi->generation = led_bdev_generation;
+ }
+}
+
+/**
+ * led_bdev_get_bdev() - Get a block device by path, prepending "/dev/" if
+ * needed.
+ * @buf: The value written to the ``link_device`` or ``unlink_device``
+ * attribute, which should be the path to a special file that
+ * represents a block device
+ * @count: The number of characters in @buf (not including its terminating
+ * null)
+ *
+ * This function is a wrapper around blkdev_get_by_path(). It first tries the
+ * path that was written to the sysfs attribute (after removing trailing
+ * whitespace). If the first attempt returns -ENOENT, it tries again with
+ * "/dev/" prepended to the path.
+ *
+ * The caller must call blkdev_put() when finished with the device.
+ *
+ * Context: Process context.
+ * Return: The block device, or an error pointer.
+ */
+static struct block_device *led_bdev_get(const char *const buf,
+ const size_t count, fmode_t mode)
+{
+ static const char dev[] = "/dev/";
+ struct block_device *bdev;
+ char *dev_path, *path;
+
+ /* sizeof(dev) includes terminating null */
+ dev_path = kmalloc(sizeof(dev) + count, GFP_KERNEL);
+ if (dev_path == NULL)
+ return ERR_PTR(-ENOMEM);
+
+ /* sizeof(dev) - 1 is compile-time equivalent of strlen(dev) */
+ memcpy(dev_path, dev, sizeof(dev) - 1);
+ path = dev_path + sizeof(dev) - 1;
+ memcpy(path, buf, count + 1); /* include terminating null */
+ strim(path);
+
+try_blkdev_get:
+ bdev = blkdev_get_by_path(path, mode, THIS_MODULE);
+ if (IS_ERR(bdev) && PTR_ERR(bdev) == -ENOENT && path != dev_path) {
+ path = dev_path;
+ goto try_blkdev_get;
+ }
+
+ kfree(dev_path);
+ return bdev;
+}
+
+/**
+ * led_bdev_link() - "Link" a block device to an LED.
+ * @led: The LED
+ * @bdi: The block device
+ *
+ * Called from link_device_store() to create the link between an LED and a
+ * block device.
+ *
+ * * Allocates & initializes link structure.
+ * * Adds block device symlink to LED's ``linked_devices`` directory.
+ * * Adds LED symlink to block devices's ``linked_leds`` directory.
+ * * Adds link to LED's list of block devices and device's list of LEDs.
+ *
+ * If the new link is the only one (i.e. no other block device/LED links
+ * already exist), schedule delayed work to periodically check for block
+ * device activity and blink LEDs.
+ *
+ * Context: Process context. Caller must hold @led_bdev_mutex.
+ * Return: 0 on success, ``-errno`` on error.
+ */
+static int led_bdev_link(struct led_bdev_led *const led,
+ struct led_bdev_bdi *const bdi)
+{
+ struct led_bdev_link *link;
+ unsigned long delay;
+ int ret;
+
+ link = kmalloc(sizeof(*link), GFP_KERNEL);
+ if (link == NULL) {
+ ret = -ENOMEM;
+ goto error_return;
+ }
+
+ /* /sys/class/block/<bdev>/linked_leds/<led> */
+ ret = sysfs_add_link_to_group(bdev_kobj(bdi->bdev),
+ led_bdev_linked_leds.name,
+ &led->led_cdev->dev->kobj,
+ led->led_cdev->name);
+ if (ret != 0)
+ goto error_free_link;
+
+ /* /sys/class/leds/<led>/linked_devices/<bdev> */
+ ret = sysfs_add_link_to_group(&led->led_cdev->dev->kobj,
+ led_bdev_linked_devs.name,
+ bdev_kobj(bdi->bdev),
+ dev_name(&bdi->bdev->bd_device));
+ if (ret != 0)
+ goto error_remove_symlink;
+
+ link->bdi = bdi;
+ link->led = led;
+ hlist_add_head(&link->led_bdis_node, &led->bdis);
+ hlist_add_head(&link->bdi_leds_node, &bdi->leds);
+
+ if (led_bdev_link_count == 0) {
+ delay = READ_ONCE(led_bdev_interval);
+ WARN_ON(!schedule_delayed_work(&led_bdev_work, delay));
+ }
+
+ ++led_bdev_link_count;
+
+ return 0;
+
+error_remove_symlink:
+ sysfs_remove_link_from_group(bdev_kobj(bdi->bdev),
+ led_bdev_linked_leds.name,
+ led->led_cdev->name);
+error_free_link:
+ kfree(link);
+error_return:
+ return ret;
+}
+
+/**
+ * unlink_device_store() - ``unlink_device`` device attribute store function.
+ * @dev: The LED device
+ * @attr: The ``unlink_device`` attribute (@dev_attr_unlink_device)
+ * @buf: The value written to the attribute, which should be the path to
+ * the special file that represents the block device to be unlinked
+ * from the LED (e.g. /dev/sda)
+ * @count: The number of characters in @buf
+ *
+ * Block device name is written to the attribute to "unlink" the block device
+ * from the LED. I.e. the LED will no longer blink to show activity on that
+ * block device.
+ *
+ * Calls led_bdev_get() to get the block device represented by the path in @buf.
+ * If the device has a BDI, searches the BDI's list of LEDs for a link to this
+ * LED and (if found) calls led_bdev_unlink() to destroy the link.
+ *
+ * Context: Process context. Takes and releases @led_bdev_mutex.
+ * Return: @count on success, ``-errno`` on error.
+ */
+static ssize_t unlink_device_store(struct device *const dev,
+ struct device_attribute *const attr,
+ const char *buf, const size_t count)
+{
+ struct led_bdev_led *const led = led_trigger_get_drvdata(dev);
+ struct block_device *bdev;
+ struct led_bdev_bdi *bdi;
+ struct led_bdev_link *link;
+ int ret;
+
+ bdev = led_bdev_get(buf, count, 0);
+ if (IS_ERR(bdev)) {
+ ret = PTR_ERR(bdev);
+ goto exit_return;
+ }
+
+ bdi = devres_find(&bdev->bd_device, led_bdev_bdi_release, NULL, NULL);
+ if (bdi == NULL) {
+ ret = -EUNATCH;
+ goto exit_put_bdev;
+ }
+
+ ret = mutex_lock_interruptible(&led_bdev_mutex);
+ if (ret != 0)
+ goto exit_put_bdev;
+
+ hlist_for_each_entry(link, &bdi->leds, bdi_leds_node) {
+
+ if (link->led == led) {
+ led_bdev_unlink(led, link, bdi, false);
+ goto exit_unlock;
+ }
+ }
+
+ ret = -EUNATCH;
+
+exit_unlock:
+ mutex_unlock(&led_bdev_mutex);
+exit_put_bdev:
+ blkdev_put(bdev, 0);
+exit_return:
+ return (ret == 0) ? count : ret;
+}
+
+/**
+ * led_bdev_unlink() - "Unlink" a block device from an LED.
+ * @led: The LED
+ * @link: The existing link between the LED and the block device
+ * @bdi: The block device
+ * @releasing: Indicates whether the BDI is being released (because the
+ * block device has been removed)
+ *
+ * Removes and frees the link between an LED and a block device.
+ *
+ * * Removes the link from the LED's list of block devices and the
+ * device's list of LEDs.
+ * * Frees the link structure.
+ * * Removes the block device symlink from the LED's ``linked_devices``
+ * directory.
+ *
+ * If the block device is **not** being released:
+ *
+ * * Removes the LED symlink from the block device's ``linked_leds``
+ * directory.
+ * * Calls led_bdev_put_bdi() to clean up the BDI, if required.
+ *
+ * If the removed link was the only one (i.e. there are no existing block
+ * device/LED links after its removal), cancels the periodic delayed work
+ * which checks for device activity.
+ *
+ * This function is called from multiple locations.
+ *
+ * * unlink_device_store() calls this function (with @releasing == ``false``)
+ * when a block device is unlinked from an LED via the ``unlink_device``
+ * sysfs attribute.
+ * * led_bdev_deactivate() calls this function (with @releasing == ``false``)
+ * for each block device linked to an LED that is being deactivated
+ * (disassociated from the trigger).
+ * * led_bdev_bdi_release() calls this function (with @releasing == ``true``)
+ * for each LED link to a block device that has been removed from the
+ * system.
+ *
+ * Context: Process context. Caller must hold @led_bdev_mutex.
+ */
+static void led_bdev_unlink(struct led_bdev_led *const led,
+ struct led_bdev_link *const link,
+ struct led_bdev_bdi *const bdi,
+ const bool releasing)
+{
+ --led_bdev_link_count;
+
+ if (led_bdev_link_count == 0)
+ WARN_ON(!cancel_delayed_work_sync(&led_bdev_work));
+
+ hlist_del(&link->led_bdis_node);
+ hlist_del(&link->bdi_leds_node);
+ kfree(link);
+
+ /* /sys/class/leds/<led>/linked_devices/<bdev> */
+ sysfs_remove_link_from_group(&led->led_cdev->dev->kobj,
+ led_bdev_linked_devs.name,
+ dev_name(&bdi->bdev->bd_device));
+
+ /*
+ * If the BDI is being released, the device's attribute groups have
+ * already been removed, and the BDI will be freed automatically.
+ */
+ if (!releasing) {
+
+ /* /sys/class/block/<bdev>/linked_leds/<led> */
+ sysfs_remove_link_from_group(bdev_kobj(bdi->bdev),
+ led_bdev_linked_leds.name,
+ led->led_cdev->name);
+ led_bdev_put_bdi(bdi);
+ }
+}
+
+/**
+ * led_bdev_put_bdi() - Remove and free a BDI, if it is no longer needed.
+ * @bdi: The BDI
+ *
+ * Does nothing if the BDI (block device) is still linked to at least one LED.
+ *
+ * If the BDI is no longer linked to any LEDs, removes the block device's
+ * ``linked_leds`` directory (attribute group), removes the BDI from the
+ * block device's resource list, and frees the BDI.
+ *
+ * Called from led_bdev_unlink() (and in the link_device_store() error path).
+ *
+ * Context: Process context. Caller must hold @led_bdev_mutex.
+ */
+static void led_bdev_put_bdi(struct led_bdev_bdi *const bdi)
+{
+ struct block_device *const bdev = bdi->bdev;
+ int ret;
+
+ if (hlist_empty(&bdi->leds)) {
+
+ sysfs_remove_group(bdev_kobj(bdev), &led_bdev_linked_leds);
+ ret = devres_destroy(&bdev->bd_device, led_bdev_bdi_release,
+ NULL, NULL);
+ WARN_ON(ret != 0);
+ }
+}
+
+/**
+ * led_bdev_deactivate() - Called when an LED is disassociated from the
+ * trigger.
+ * @led_cdev: The LED
+ *
+ * Calls led_bdev_unlink() for each block device linked to the LED, removes
+ * the LED from the @led_bdev_leds list, and frees the @led_bdev_led structure.
+ *
+ * Context: Process context. Takes and releases @led_bdev_mutex.
+ */
+static void led_bdev_deactivate(struct led_classdev *const led_cdev)
+{
+ struct led_bdev_led *const led = led_get_trigger_data(led_cdev);
+ struct led_bdev_link *link;
+ struct hlist_node *next;
+
+ mutex_lock(&led_bdev_mutex);
+
+ hlist_for_each_entry_safe (link, next, &led->bdis, led_bdis_node)
+ led_bdev_unlink(led, link, link->bdi, false);
+
+ hlist_del(&led->leds_node);
+ kfree(led);
+
+ mutex_unlock(&led_bdev_mutex);
+}
+
+/**
+ * led_bdev_bdi_release() - BDI device resource release function.
+ * @dev: The block device
+ * @res: The BDI
+ *
+ * Called by the driver core when a block device with a BDI is removed from the
+ * system. Calls led_bdev_unlink() for each LED linked to the block device.
+ *
+ * Context: Process context. Takes and releases @led_bdev_mutex.
+ */
+static void led_bdev_bdi_release(struct device *const dev, void *const res)
+{
+ struct led_bdev_bdi *const bdi = res;
+ struct led_bdev_link *link;
+ struct hlist_node *next;
+
+ mutex_lock(&led_bdev_mutex);
+
+ hlist_for_each_entry_safe (link, next, &bdi->leds, bdi_leds_node)
+ led_bdev_unlink(link->led, link, bdi, true);
+
+ mutex_unlock(&led_bdev_mutex);
+}
+
+/**
+ * led_bdev_process() - Check linked devices for activity and blink LEDs.
+ * @work: Delayed work (@led_bdev_work)
+ *
+ * Iterates through block devices linked to LEDs and calls led_bdev_update_bdi()
+ * to update the BDI's activity counters. If a particular LED hasn't already
+ * been blinked, calls led_bdev_blink() to blink the LED if appropriate for that
+ * device's activity.
+ *
+ * When finished, schedules itself to run again after @led_bdev_interval
+ * jiffies.
+ *
+ * Context: Process context. Takes and releases @led_bdev_mutex.
+ */
+static void led_bdev_process(struct work_struct *const work)
+{
+ struct led_bdev_led *led;
+ struct led_bdev_link *link;
+ unsigned long delay;
+
+ if (!mutex_trylock(&led_bdev_mutex))
+ goto exit_reschedule;
+
+ hlist_for_each_entry (led, &led_bdev_leds, leds_node) {
+
+ bool blinked = false;
+
+ hlist_for_each_entry (link, &led->bdis, led_bdis_node) {
+
+ led_bdev_update_bdi(link->bdi);
+ if (!blinked)
+ blinked = led_bdev_blink(led, link->bdi);
+ }
+ }
+
+ ++led_bdev_generation;
+
+ mutex_unlock(&led_bdev_mutex);
+
+exit_reschedule:
+ delay = READ_ONCE(led_bdev_interval);
+ WARN_ON_ONCE(!schedule_delayed_work(&led_bdev_work, delay));
+}
+
+/**
+ * led_bdev_blink() - Blink an LED, if the correct type of activity has occurred
+ * on the block device.
+ * @led: The LED
+ * @bdi: The block device
+ *
+ * Context: Process context. Caller must hold @led_bdev_mutex.
+ * Return: ``true`` if the LED is blinked, ``false`` if not.
+ */
+static bool led_bdev_blink(const struct led_bdev_led *const led,
+ const struct led_bdev_bdi *const bdi)
+{
+ unsigned long delay_on, delay_off;
+
+ if ((bdi->read_act && led->mode != LED_BDEV_MODE_WO)
+ || (bdi->write_act && led->mode != LED_BDEV_MODE_RO)) {
+
+ delay_on = READ_ONCE(led->blink_msec);
+ delay_off = 1; /* 0 leaves LED turned on */
+
+ led_blink_set_oneshot(led->led_cdev, &delay_on, &delay_off, 0);
+ return true;
+ }
+
+ return false;
+}
+
+/**
+ * blink_time_show() - ``blink_time`` device attribute show function.
+ * @dev: The LED device
+ * @attr: The ``blink_time`` attribute (@dev_attr_blink_time)
+ * @buf: Output buffer
+ *
+ * Writes the current value of the LED's @blink_msec to @buf.
+ *
+ * Context: Process context.
+ * Return: The number of characters written to @buf.
+ */
+static ssize_t blink_time_show(struct device *const dev,
+ struct device_attribute *const attr,
+ char *const buf)
+{
+ const struct led_bdev_led *const led = led_trigger_get_drvdata(dev);
+
+ return sprintf(buf, "%u\n", READ_ONCE(led->blink_msec));
+}
+
+/**
+ * blink_time_store() - ``blink_time`` device attribute store function.
+ * @dev: The LED device
+ * @attr: The ``blink_time`` attribute (@dev_attr_blink_time)
+ * @buf: The new value (as written to the sysfs attribute)
+ * @count: The number of characters in @buf
+ *
+ * Sets the LED's @blink_msec (the duration in milliseconds of one blink).
+ *
+ * Context: Process context.
+ * Return: @count on success, ``-errno`` on error.
+ */
+static ssize_t blink_time_store(struct device *const dev,
+ struct device_attribute *const attr,
+ const char *const buf, const size_t count)
+{
+ struct led_bdev_led *const led = led_trigger_get_drvdata(dev);
+ unsigned int value;
+ int ret;
+
+ ret = kstrtouint(buf, 0, &value);
+ if (ret != 0)
+ return ret;
+
+ if (value < LED_BDEV_MIN_BLINK)
+ return -ERANGE;
+
+ WRITE_ONCE(led->blink_msec, value);
+ return count;
+}
+
+/* Data for mode_show() & mode_store() */
+static const struct {
+ char name[sizeof("write")]; /* longest name */
+ char show[sizeof("[read] write rw\n")]; /* all the same size */
+} led_bdev_modes[] = {
+ [LED_BDEV_MODE_RO] = {
+ .name = "read",
+ .show = "[read] write rw\n",
+ },
+ [LED_BDEV_MODE_WO] = {
+ .name = "write",
+ .show = "read [write] rw\n",
+ },
+ [LED_BDEV_MODE_RW] = {
+ .name = "rw",
+ .show = "read write [rw]\n",
+ },
+};
+
+/**
+ * mode_show() - ``mode`` device attribute show function.
+ * @dev: The LED device
+ * @attr: The ``mode`` attribute (@dev_attr_mode)
+ * @buf: Output buffer
+ *
+ * Writes the current value of the LED's @mode to @buf.
+ *
+ * Context: Process context.
+ * Return: The number of characters written to @buf.
+ */
+static ssize_t mode_show(struct device *const dev,
+ struct device_attribute *const attr, char *const buf)
+{
+ const struct led_bdev_led *const led = led_trigger_get_drvdata(dev);
+
+ return sprintf(buf, led_bdev_modes[READ_ONCE(led->mode)].show);
+}
+
+/**
+ * mode_store() - ``mode`` device attribute store function.
+ * @dev: The LED device
+ * @attr: The ``mode`` attribute (@dev_attr_mode)
+ * @buf: The new value (as written to the sysfs attribute)
+ * @count: The number of characters in @buf
+ *
+ * Sets the LED's @mode (``read``, ``write``, or ``rw``).
+ *
+ * Context: Process context.
+ * Return: @count on success, ``-errno`` on error.
+ */
+static ssize_t mode_store(struct device *const dev,
+ struct device_attribute *const attr,
+ const char *const buf, const size_t count)
+{
+ struct led_bdev_led *const led = led_trigger_get_drvdata(dev);
+ enum led_bdev_mode mode;
+
+ for (mode = LED_BDEV_MODE_RO; mode <= LED_BDEV_MODE_RW; ++mode) {
+
+ if (sysfs_streq(led_bdev_modes[mode].name, buf)) {
+ WRITE_ONCE(led->mode, mode);
+ return count;
+ }
+ }
+
+ return -EINVAL;
+}
+
+/**
+ * interval_show() - ``interval`` class attribute show function.
+ * @class: The ``ledtrig_blkdev`` class (@led_bdev_class)
+ * @attr: The ``interval`` attribute (@class_attr_interval)
+ * @buf: Output buffer
+ *
+ * Writes the current value of @led_bdev_interval to @buf.
+ *
+ * Context: Process context.
+ * Return: The number of characters written to @buf.
+ */
+static ssize_t interval_show(struct class *const class,
+ struct class_attribute *const attr,
+ char *const buf)
+{
+ return sprintf(buf, "%u\n",
+ jiffies_to_msecs(READ_ONCE(led_bdev_interval)));
+}
+
+/**
+ * interval_store() - ``interval`` class attribute store function
+ * @class: The ``ledtrig_blkdev`` class (@led_bdev_class)
+ * @attr: The ``interval`` attribute (@class_attr_interval)
+ * @buf: The new value (as written to the sysfs attribute)
+ * @count: The number of characters in @buf
+ *
+ * Sets @led_bdev_interval (after converting to jiffies).
+ *
+ * Context: Process context.
+ * Return: @count on success, ``-errno`` on error.
+ */
+static ssize_t interval_store(struct class *const class,
+ struct class_attribute *const attr,
+ const char *const buf, const size_t count)
+{
+ unsigned int value;
+ int ret;
+
+ ret = kstrtouint(buf, 0, &value);
+ if (ret != 0)
+ return ret;
+
+ if (value < LED_BDEV_MIN_INT)
+ return -ERANGE;
+
+ WRITE_ONCE(led_bdev_interval, msecs_to_jiffies(value));
+
+ return count;
+}
+
+/* Device and class attributes */
+static DEVICE_ATTR_WO(link_device);
+static DEVICE_ATTR_WO(unlink_device);
+static DEVICE_ATTR_RW(blink_time);
+static DEVICE_ATTR_RW(mode);
+static CLASS_ATTR_RW(interval);
+
+/* Device attributes in LED directory (/sys/class/leds/<led>/...) */
+static struct attribute *led_bdev_attrs[] = {
+ &dev_attr_link_device.attr,
+ &dev_attr_unlink_device.attr,
+ &dev_attr_blink_time.attr,
+ &dev_attr_mode.attr,
+ NULL
+};
+
+/* Unnamed attribute group == no subdirectory */
+static const struct attribute_group led_bdev_attr_group = {
+ .attrs = led_bdev_attrs,
+};
+
+/* Attribute groups for the trigger */
+static const struct attribute_group *led_bdev_attr_groups[] = {
+ &led_bdev_attr_group, /* /sys/class/leds/<led>/... */
+ &led_bdev_linked_devs, /* /sys/class/leds/<led>/linked_devices/ */
+ NULL
+};
+
+/* Trigger registration data */
+static struct led_trigger led_bdev_trigger = {
+ .name = "blkdev",
+ .activate = led_bdev_activate,
+ .deactivate = led_bdev_deactivate,
+ .groups = led_bdev_attr_groups,
+};
+
+/**
+ * led_bdev_init() - Block device LED trigger initialization.
+ *
+ * Converts default @led_bdev_interval from milliseconds to jiffies, creates
+ * the ``/sys/class/ledtrig_blkdev/interval`` attribute, and registers the LED
+ * trigger.
+ *
+ * Return: 0 on success, ``-errno`` on failure.
+ */
+static int __init led_bdev_init(void)
+{
+ int ret;
+
+ WRITE_ONCE(led_bdev_interval,
+ msecs_to_jiffies(LED_BDEV_INTERVAL));
+
+ led_bdev_class = class_create(THIS_MODULE, "ledtrig_blkdev");
+ if (IS_ERR(led_bdev_class)) {
+ ret = PTR_ERR(led_bdev_class);
+ goto exit_return;
+ }
+
+ ret = class_create_file(led_bdev_class, &class_attr_interval);
+ if (ret != 0)
+ goto exit_destroy_class;
+
+ ret = led_trigger_register(&led_bdev_trigger);
+
+exit_destroy_class:
+ if (ret != 0)
+ class_destroy(led_bdev_class); /* removes the attribute file */
+exit_return:
+ return ret;
+}
+module_init(led_bdev_init);
+
+/**
+ * led_bdev_exit() - Block device LED trigger module exit.
+ *
+ * Unregisters the LED trigger and removes the
+ * ``/sys/class/ledtrig_blkdev/interval`` attribute.
+ */
+static void __exit led_bdev_exit(void)
+{
+ led_trigger_unregister(&led_bdev_trigger);
+ class_destroy(led_bdev_class);
+}
+module_exit(led_bdev_exit);
+
+MODULE_DESCRIPTION("Block device LED trigger");
+MODULE_AUTHOR("Ian Pilcher <arequipeno@xxxxxxxxx>");
+MODULE_LICENSE("GPL v2");
--
2.31.1
