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 | 965 ++++++++++++++++++++++++++
3 files changed, 975 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..feead76c2e9d
--- /dev/null
+++ b/drivers/leds/trigger/ledtrig-blkdev.c
@@ -0,0 +1,965 @@
+// 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>
+#include <linux/xarray.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
+
+/* Mode for blkdev_get_by_path() & blkdev_put() */
+#define LED_BDEV_FMODE 0
+
+/* Device activity type that will make LED blink */
+enum led_bdev_led_mode {
+ LED_BDEV_MODE_RO = 0,
+ LED_BDEV_MODE_WO = 1,
+ LED_BDEV_MODE_RW = 2
+};
+
+/* When unlinking a block device from an LED, is the blkdev being released? */
+enum led_bdev_unlink_mode {
+ LED_BDEV_RELEASING,
+ LED_BDEV_NOT_RELEASING
+};
+
+/* An "LED block device" (LBD) - 1 per blkdev linked to at least 1 LED */
+struct led_bdev_lbd {
+ unsigned long index;
+ struct block_device *bdev;
+ struct xarray linked_leds;
+ unsigned long read_ios;
+ unsigned long write_ios;
+ unsigned int generation;
+ bool read_act;
+ bool write_act;
+};
+
+/* Every LED associated with the blkdev trigger gets one of these */
+struct led_bdev_led {
+ unsigned long index;
+ struct led_classdev *led_cdev;
+ unsigned int blink_msec;
+ struct xarray linked_lbds;
+ struct hlist_node all_leds_node;
+ enum led_bdev_led_mode mode;
+};
+
+/* Forward declarations to make this file compile in a more readable order */
+static void led_bdev_process(struct work_struct *work);
+static struct led_bdev_lbd *led_bdev_get_lbd(const char *buf, size_t size);
+static struct block_device *led_bdev_get_bdev(const char *buf, size_t size,
+ fmode_t mode);
+static int led_bdev_link(struct led_bdev_led *led, struct led_bdev_lbd *lbd);
+static void led_bdev_put_lbd(struct led_bdev_lbd *lbd);
+static void led_bdev_lbd_release(struct device *dev, void *res);
+static void led_bdev_unlink(struct led_bdev_led *led,
+ struct led_bdev_lbd *lbd,
+ enum led_bdev_unlink_mode unlink_mode);
+static void led_bdev_update_lbd(struct led_bdev_lbd *lbd);
+static bool led_bdev_blink(const struct led_bdev_led *led,
+ const struct led_bdev_lbd *lbd);
+
+/* Index for next LBD or LED */
+static unsigned long led_bdev_next_index;
+
+/* Protects everything except atomic sysfs attributes */
+static DEFINE_MUTEX(led_bdev_mutex);
+
+/* All LEDs associated with the trigger */
+static HLIST_HEAD(led_bdev_all_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_all_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;
+
+ if (led_bdev_next_index == ULONG_MAX) {
+ ret = -EOVERFLOW;
+ goto exit_return;
+ }
+
+ led = kmalloc(sizeof(*led), GFP_KERNEL);
+ if (led == NULL) {
+ ret = -ENOMEM;
+ goto exit_return;
+ }
+
+ led->index = led_bdev_next_index++;
+ led->led_cdev = led_cdev;
+ led->blink_msec = LED_BDEV_BLINK_MSEC;
+ led->mode = LED_BDEV_MODE_RW;
+ xa_init(&led->linked_lbds);
+
+ ret = mutex_lock_interruptible(&led_bdev_mutex);
+ if (ret != 0)
+ goto exit_free;
+
+ hlist_add_head(&led->all_leds_node, &led_bdev_all_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_lbd() to find or create the LBD 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);
+ struct led_bdev_lbd *lbd;
+ int ret;
+
+ ret = mutex_lock_interruptible(&led_bdev_mutex);
+ if (ret != 0)
+ goto exit_return;
+
+ lbd = led_bdev_get_lbd(buf, count);
+ if (IS_ERR(lbd)) {
+ ret = PTR_ERR(lbd);
+ goto exit_unlock;
+ }
+
+ if (xa_load(&lbd->linked_leds, led->index) != NULL) {
+ ret = -EEXIST;
+ goto exit_put_lbd;
+ }
+
+ ret = led_bdev_link(led, lbd);
+
+exit_put_lbd:
+ if (ret != 0)
+ led_bdev_put_lbd(lbd);
+exit_unlock:
+ mutex_unlock(&led_bdev_mutex);
+exit_return:
+ return (ret == 0) ? count : ret;
+}
+
+/**
+ * led_bdev_get_lbd() - Find or create the LBD 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 an LBD (because it is already linked to an LED),
+ * simply returns the existing LBD.
+ *
+ * Otherwise, allocates a new LBD (as a device resource), creates the block
+ * device's ``linked_leds`` directory (attribute group), calls
+ * led_bdev_update_lbd() to set the LBD's activity counters, and adds the LBD
+ * resource to the block device.
+ *
+ * Context: Process context. Caller must hold @led_bdev_mutex.
+ * Return: Pointer to the LBD, error pointer on error.
+ */
+static struct led_bdev_lbd *led_bdev_get_lbd(const char *const buf,
+ const size_t count)
+{
+ struct block_device *bdev;
+ struct led_bdev_lbd *lbd;
+ int ret;
+
+ bdev = led_bdev_get_bdev(buf, count, LED_BDEV_FMODE);
+ if (IS_ERR(bdev)) {
+ ret = PTR_ERR(bdev);
+ goto exit_return;
+ }
+
+ lbd = devres_find(&bdev->bd_device, led_bdev_lbd_release, NULL, NULL);
+ if (lbd != NULL) {
+ ret = 0;
+ goto exit_put_bdev;
+ }
+
+ if (led_bdev_next_index == ULONG_MAX) {
+ ret = -EOVERFLOW;
+ goto exit_put_bdev;
+ }
+
+ lbd = devres_alloc(led_bdev_lbd_release, sizeof(*lbd), GFP_KERNEL);
+ if (lbd == NULL) {
+ ret = -ENOMEM;
+ goto exit_put_bdev;
+ }
+
+ ret = sysfs_create_group(bdev_kobj(bdev), &led_bdev_linked_leds);
+ if (ret != 0)
+ goto exit_free_lbd;
+
+ lbd->index = led_bdev_next_index++;
+ lbd->bdev = bdev;
+ xa_init(&lbd->linked_leds);
+
+ /* Ensure that led_bdev_update_lbd() updates the LBD */
+ lbd->generation = led_bdev_generation - 1;
+ led_bdev_update_lbd(lbd);
+ /* Don't blink for activity that may have happened long ago */
+ lbd->read_act = false;
+ lbd->write_act = false;
+
+ devres_add(&bdev->bd_device, lbd);
+
+exit_free_lbd:
+ if (ret != 0)
+ devres_free(lbd);
+exit_put_bdev:
+ blkdev_put(bdev, LED_BDEV_FMODE); /* Allow the device to be released */
+exit_return:
+ return (ret == 0) ? lbd : ERR_PTR(ret);
+}
+
+/**
+ * led_bdev_get_bdev() - Get a block device by path.
+ * @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)
+ *
+ * Copies @buf to a writable buffer, trims the trailing newline (if any), and
+ * calls blkdev_get_by_path() to resolve the block device.
+ *
+ * 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_bdev(const char *const buf,
+ const size_t count,
+ const fmode_t mode)
+{
+ struct block_device *bdev;
+ char *path;
+
+ path = kmemdup(buf, count + 1, GFP_KERNEL); /* include null */
+ if (path == NULL)
+ return ERR_PTR(-ENOMEM);
+
+ if (path[count - 1] == '\n')
+ path[count - 1] = 0;
+
+ bdev = blkdev_get_by_path(path, mode, THIS_MODULE);
+ kfree(path);
+ return bdev;
+}
+
+/**
+ * led_bdev_update_lbd() - Update an LBD's activity counters for the current
+ * generation
+ * @lbd: The LBD
+ *
+ * Does nothing if the LBD has already been updated during this generation.
+ *
+ * Otherwise, updates the LBD'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_lbd(struct led_bdev_lbd *const lbd)
+{
+ unsigned long read_ios, write_ios;
+
+ if (lbd->generation != led_bdev_generation) {
+
+ read_ios = part_stat_read(lbd->bdev, ios[STAT_READ]);
+
+ write_ios = part_stat_read(lbd->bdev, ios[STAT_WRITE])
+ + part_stat_read(lbd->bdev, ios[STAT_DISCARD])
+ + part_stat_read(lbd->bdev, ios[STAT_FLUSH]);
+
+ if (lbd->read_ios != read_ios) {
+ lbd->read_act = true;
+ lbd->read_ios = read_ios;
+ } else {
+ lbd->read_act = false;
+ }
+
+ if (lbd->write_ios != write_ios) {
+ lbd->write_act = true;
+ lbd->write_ios = write_ios;
+ } else {
+ lbd->write_act = false;
+ }
+
+ lbd->generation = led_bdev_generation;
+ }
+}
+
+/**
+ * led_bdev_link() - "Link" a block device to an LED.
+ * @led: The LED
+ * @lbd: The block device
+ *
+ * Called from link_device_store() to create the link between an LED and a
+ * block device.
+ *
+ * * Adds block device symlink to LED's ``linked_devices`` directory.
+ * * Adds LED symlink to block devices's ``linked_leds`` directory.
+ * * Adds the LBD to the LED's @linked_lbds and adds the LED to the LBD's
+ * @linked_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_lbd *const lbd)
+{
+ unsigned long delay;
+ int ret;
+
+ ret = xa_insert(&lbd->linked_leds, led->index, led, GFP_KERNEL);
+ if (ret != 0)
+ goto error_return;
+
+ ret = xa_insert(&led->linked_lbds, lbd->index, lbd, GFP_KERNEL);
+ if (ret != 0)
+ goto error_erase_led;
+
+ /* /sys/class/block/<bdev>/linked_leds/<led> */
+ ret = sysfs_add_link_to_group(bdev_kobj(lbd->bdev),
+ led_bdev_linked_leds.name,
+ &led->led_cdev->dev->kobj,
+ led->led_cdev->name);
+ if (ret != 0)
+ goto error_erase_lbd;
+
+ /* /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(lbd->bdev),
+ dev_name(&lbd->bdev->bd_device));
+ if (ret != 0)
+ goto error_remove_symlink;
+
+ 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(lbd->bdev),
+ led_bdev_linked_leds.name,
+ led->led_cdev->name);
+error_erase_lbd:
+ xa_erase(&led->linked_lbds, lbd->index);
+error_erase_led:
+ xa_erase(&lbd->linked_leds, led->index);
+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 an LBD, searches the LBD'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 *const buf, const size_t count)
+{
+ struct led_bdev_led *const led = led_trigger_get_drvdata(dev);
+ struct block_device *bdev;
+ struct led_bdev_lbd *lbd;
+ int ret;
+
+ bdev = led_bdev_get_bdev(buf, count, LED_BDEV_FMODE);
+ if (IS_ERR(bdev)) {
+ ret = PTR_ERR(bdev);
+ goto exit_return;
+ }
+
+ ret = mutex_lock_interruptible(&led_bdev_mutex);
+ if (ret != 0)
+ goto exit_put_bdev;
+
+ lbd = devres_find(&bdev->bd_device, led_bdev_lbd_release, NULL, NULL);
+ if (lbd == NULL) {
+ ret = -EUNATCH; /* bdev isn't linked to any LED */
+ goto exit_unlock;
+ }
+
+ if (xa_load(&lbd->linked_leds, led->index) == NULL) {
+ ret = -EUNATCH; /* bdev isn't linked to this LED */
+ goto exit_unlock;
+ }
+
+ led_bdev_unlink(led, lbd, LED_BDEV_NOT_RELEASING);
+
+exit_unlock:
+ mutex_unlock(&led_bdev_mutex);
+exit_put_bdev:
+ blkdev_put(bdev, LED_BDEV_FMODE);
+exit_return:
+ return (ret == 0) ? count : ret;
+}
+
+/**
+ * led_bdev_unlink() - "Unlink" a block device from an LED.
+ * @led: The LED
+ * @lbd: The block device
+ * @unlink_mode: Indicates whether the LBD is being released (because the
+ * block device has been removed)
+ *
+ * Removes the link between an LED and a block device.
+ *
+ * * Removes the LBD from the LED's @linked_lbds and removes the LED from the
+ * LBD's @linked_leds.
+ * * 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_lbd() to clean up the LBD, 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 when a block device is unlinked
+ * from an LED via the ``unlink_device`` sysfs attribute. (@unlink_mode ==
+ * ``LED_BDEV_NOT_RELEASING``)
+ * * led_bdev_deactivate() calls this function for each block device linked to
+ * an LED that is being deactivated (disassociated from the trigger).
+ * (@unlink_mode == ``LED_BDEV_NOT_RELEASING``).
+ * * led_bdev_lbd_release() calls this function for each LED linked to a block
+ * device that has been removed from the system. (@unlink_mode ==
+ * ``LED_BDEV_RELEASING).
+ *
+ * Context: Process context. Caller must hold @led_bdev_mutex.
+ */
+static void led_bdev_unlink(struct led_bdev_led *const led,
+ struct led_bdev_lbd *const lbd,
+ const enum led_bdev_unlink_mode unlink_mode)
+{
+ --led_bdev_link_count;
+
+ if (led_bdev_link_count == 0)
+ WARN_ON(!cancel_delayed_work_sync(&led_bdev_work));
+
+ xa_erase(&lbd->linked_leds, led->index);
+ xa_erase(&led->linked_lbds, lbd->index);
+
+ /* /sys/class/leds/<led>/linked_devices/<bdev> */
+ sysfs_remove_link_from_group(&led->led_cdev->dev->kobj,
+ led_bdev_linked_devs.name,
+ dev_name(&lbd->bdev->bd_device));
+
+ /*
+ * If the LBD is being released, the device's attribute groups have
+ * already been removed, and the LBD will be freed automatically.
+ */
+ if (unlink_mode == LED_BDEV_NOT_RELEASING) {
+
+ /* /sys/class/block/<bdev>/linked_leds/<led> */
+ sysfs_remove_link_from_group(bdev_kobj(lbd->bdev),
+ led_bdev_linked_leds.name,
+ led->led_cdev->name);
+ led_bdev_put_lbd(lbd);
+ }
+}
+
+/**
+ * led_bdev_put_lbd() - Remove and free an LBD, if it is no longer needed.
+ * @lbd: The LBD
+ *
+ * Does nothing if the LBD (block device) is still linked to at least one LED.
+ *
+ * If the LBD is no longer linked to any LEDs, removes the block device's
+ * ``linked_leds`` directory (attribute group), removes the LBD from the
+ * block device's resource list, and frees the LBD.
+ *
+ * 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_lbd(struct led_bdev_lbd *const lbd)
+{
+ struct block_device *const bdev = lbd->bdev;
+ int ret;
+
+ if (xa_empty(&lbd->linked_leds)) {
+
+ sysfs_remove_group(bdev_kobj(bdev), &led_bdev_linked_leds);
+ ret = devres_destroy(&bdev->bd_device, led_bdev_lbd_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_all_leds list, and frees the @led_bdev_led.
+ *
+ * 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_lbd *lbd;
+ unsigned long index;
+
+ mutex_lock(&led_bdev_mutex);
+
+ xa_for_each (&led->linked_lbds, index, lbd)
+ led_bdev_unlink(led, lbd, LED_BDEV_NOT_RELEASING);
+
+ hlist_del(&led->all_leds_node);
+ kfree(led);
+
+ mutex_unlock(&led_bdev_mutex);
+}
+
+/**
+ * led_bdev_lbd_release() - LBD device resource release function.
+ * @dev: The block device
+ * @res: The LBD
+ *
+ * Called by the driver core when a block device with an LBD 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_lbd_release(struct device *const dev, void *const res)
+{
+ struct led_bdev_lbd *const lbd = res;
+ struct led_bdev_led *led;
+ unsigned long index;
+
+ mutex_lock(&led_bdev_mutex);
+
+ xa_for_each (&lbd->linked_leds, index, led)
+ led_bdev_unlink(led, lbd, LED_BDEV_RELEASING);
+
+ 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_lbd()
+ * to update the LBD'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;
+ unsigned long delay;
+
+ if (!mutex_trylock(&led_bdev_mutex))
+ goto exit_reschedule;
+
+ hlist_for_each_entry (led, &led_bdev_all_leds, all_leds_node) {
+
+ struct led_bdev_lbd *lbd;
+ unsigned long index;
+ bool blinked = false;
+
+ xa_for_each (&led->linked_lbds, index, lbd) {
+
+ led_bdev_update_lbd(lbd);
+ if (!blinked)
+ blinked = led_bdev_blink(led, lbd);
+ }
+ }
+
+ ++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
+ * @lbd: 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_lbd *const lbd)
+{
+ unsigned long delay_on, delay_off;
+
+ if ((lbd->read_act && led->mode != LED_BDEV_MODE_WO)
+ || (lbd->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;
+}
+
+/**
+ * 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)
+{
+ static const char modes[][sizeof("[read] write rw\n")] = {
+ [LED_BDEV_MODE_RO] = "[read] write rw\n",
+ [LED_BDEV_MODE_WO] = "read [write] rw\n",
+ [LED_BDEV_MODE_RW] = "read write [rw]\n"
+ };
+
+ const struct led_bdev_led *const led = led_trigger_get_drvdata(dev);
+
+ return sprintf(buf, modes[READ_ONCE(led->mode)]);
+}
+
+/**
+ * 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)
+{
+ static const char modes[][sizeof("write")] = {
+ [LED_BDEV_MODE_RO] = "read",
+ [LED_BDEV_MODE_WO] = "write", /* longest */
+ [LED_BDEV_MODE_RW] = "rw"
+ };
+
+ struct led_bdev_led *const led = led_trigger_get_drvdata(dev);
+ enum led_bdev_led_mode mode;
+
+ for (mode = LED_BDEV_MODE_RO; mode <= LED_BDEV_MODE_RW; ++mode) {
+
+ if (sysfs_streq(modes[mode], 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
