[PATCH 00/18] Introduce block device LED trigger

Ian Pilcher
2021-09-03T20:45:59Z

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

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2.31.1