[PATCH 00/18] Introduce block device LED trigger

[Ian Pilcher <arequipeno@gmail.com>]

This patch series adds a new "blkdev" LED trigger for disk (or other block
device) activity LEDs.

It has the following functionality.

* Supports all types of block devices, including virtual devices
  (unlike the existing disk trigger which only works with ATA devices).

* LEDs can be configured to show read activity, write activity, or both.

* Supports multiple devices and multiple LEDs in arbitrary many-to-many
  configurations.  For example, it is possible to configure multiple
  devices with device-specific read activity LEDs and a shared write
  activity LED.  (See Documentation/leds/ledtrig-blkdev.rst in the first
  patch.)

* Doesn't add any overhead in the I/O path.  Like the netdev LED trigger,
  it periodically checks the configured devices for activity and blinks
  its LEDs as appropriate.

* Blink duration (per LED) and interval between activity checks (global)
  are configurable.

* Requires minimal changes to the block subsystem.

  - Adds 1 pointer to struct gendisk,

  - Adds (inline function) call in device_add_disk() to ensure that the
    pointer is initialized to NULL (as protection against any drivers
    that allocate a gendisk themselves and don't use kzalloc()), and

  - Adds call in del_gendisk() to remove a device from the trigger when
    that device is being removed.

  These changes are all in patch #4, "block: Add block device LED trigger
  integrations."

* The trigger can be mostly built as a module.

  When the trigger is modular, a small portion is built in to provide a
  "stub" function which can be called from del_gendisk().  The stub calls
  into the modular code via a function pointer when needed.  The trigger
  also needs the ability to find gendisk's by name, which requires access
  to the un-exported block_class and disk_type symbols.

NOTES:

* This patch series applies cleanly to the linux-block and linux-next
  (20210903) trees.  All patches other than the block subsystem patch
  (patch #4) apply cleanly to the linux-leds tree.

* All patches compile (modulo warnings) with the trigger disabled,
  modular, or built-in.

Ian Pilcher (18):
  docs: Add block device (blkdev) LED trigger documentation
  ledtrig-blkdev: Add build infra for block device LED trigger
  ledtrig-blkdev: Add function placeholders needed by block changes
  block: Add block device LED trigger integrations
  ledtrig-blkdev: Implement functions called from block subsystem
  ledtrig-blkdev: Add function to get gendisk by name
  ledtrig-blkdev: Add constants, data types, and global variables
  ledtrig-blkdev: Add miscellaneous helper functions
  ledtrig-blkdev: Periodically check devices for activity & blink LEDs
  ledtrig-blkdev: Add function to associate the trigger with an LED
  ledtrig-blkdev: Add function to associate a device with an LED
  ledtrig-blkdev: Add function to remove LED/device association
  ledtrig-blkdev: Add function to disassociate a device from all LEDs
  ledtrig-blkdev: Add function to disassociate an LED from the trigger
  ledtrig-blkdev: Add sysfs attributes to [un]link LEDs & devices
  ledtrig-blkdev: Add blink_time & interval sysfs attributes
  ledtrig-blkdev: Add mode (read/write/rw) sysfs attributue
  ledtrig-blkdev: Add initialization & exit functions

 Documentation/ABI/testing/sysfs-block         |   9 +
 .../testing/sysfs-class-led-trigger-blkdev    |  48 ++
 Documentation/leds/index.rst                  |   1 +
 Documentation/leds/ledtrig-blkdev.rst         | 144 ++++
 block/genhd.c                                 |   4 +
 drivers/leds/trigger/Kconfig                  |  18 +
 drivers/leds/trigger/Makefile                 |   2 +
 drivers/leds/trigger/ledtrig-blkdev-core.c    |  78 ++
 drivers/leds/trigger/ledtrig-blkdev.c         | 767 ++++++++++++++++++
 drivers/leds/trigger/ledtrig-blkdev.h         |  27 +
 include/linux/genhd.h                         |   3 +
 include/linux/leds.h                          |  20 +
 12 files changed, 1121 insertions(+)
 create mode 100644 Documentation/ABI/testing/sysfs-class-led-trigger-blkdev
 create mode 100644 Documentation/leds/ledtrig-blkdev.rst
 create mode 100644 drivers/leds/trigger/ledtrig-blkdev-core.c
 create mode 100644 drivers/leds/trigger/ledtrig-blkdev.c
 create mode 100644 drivers/leds/trigger/ledtrig-blkdev.h

-- 
2.31.1