Add Documentation/ABI/testing/sysfs-class-led-trigger-blkdev to document: * /sys/class/leds/<led>/blink_on * /sys/class/leds/<led>/blink_off * /sys/class/leds/<led>/block_devices Add /sys/block/<disk>/led to Documentation/ABI/testing/sysfs-block Add usage overview in Documentation/block/blk-ledtrig.rst Signed-off-by: Ian Pilcher <arequipeno@gmail.com> --- Documentation/ABI/testing/sysfs-block | 16 ++++ .../testing/sysfs-class-led-trigger-blkdev | 28 +++++++ Documentation/block/blk-ledtrig.rst | 79 +++++++++++++++++++ Documentation/block/index.rst | 1 + 4 files changed, 124 insertions(+) create mode 100644 Documentation/ABI/testing/sysfs-class-led-trigger-blkdev create mode 100644 Documentation/block/blk-ledtrig.rst diff --git a/Documentation/ABI/testing/sysfs-block b/Documentation/ABI/testing/sysfs-block index e34cdeeeb9d4..36253fff25b2 100644 --- a/Documentation/ABI/testing/sysfs-block +++ b/Documentation/ABI/testing/sysfs-block @@ -316,3 +316,19 @@ Description: does not complete in this time then the block driver timeout handler is invoked. That timeout handler can decide to retry the request, to fail it or to start a device recovery strategy. + +What: /sys/block/<disk>/led +Date: August 2021 +Contact: Ian Pilcher <arequipeno@gmail.com> +Description: + Set the LED associated with this block device (or show available + LEDs and the currently selected LED, if any). + + Reading the attribute will display the available LEDs (LEDs that + are associated with the blkdev LED trigger). The currently + selected LED is enclosed in square brackets. To clear the + device's LED association write 'none' (without the quotes) or + an empty string/line to the attribute. + + See Documentation/ABI/testing/sysfs-class-led-trigger-blkdev and + Documentation/block/blk-ledtrig.rst.) diff --git a/Documentation/ABI/testing/sysfs-class-led-trigger-blkdev b/Documentation/ABI/testing/sysfs-class-led-trigger-blkdev new file mode 100644 index 000000000000..1139a099a3cc --- /dev/null +++ b/Documentation/ABI/testing/sysfs-class-led-trigger-blkdev @@ -0,0 +1,28 @@ +What: /sys/class/leds/<led>/blink_on +Date: August 2021 +Contact: Ian Pilcher <arequipeno@gmail.com> +Description: + Time (in milliseconds) that the LED will be on during a single + "blink". + +What: /sys/class/leds/<led>/blink_off +Date: August 2021 +Contact: Ian Pilcher <arequipeno@gmail.com> +Description: + Time (in milliseconds) that the LED will be off during a single + "blink". Effectively the amount of time that the LED will be + off before the next blink, when the associated block device(s) + are continuously active. + +What: /sys/class/leds/<led>/block_devices +Date: August 2021 +Contact: Ian Pilcher <arequipeno@gmail.com> +Description: + Directory containing links to all block devices that are + associated with this LED. + + Once an LED has been associated with the blkdev trigger, a block + device can be associated with that LED by writing the LED name + to the device's /sys/[class/]block/<disk>/led attribute. (See + Documentation/ABI/testing/sysfs-block and + Documentation/block/blk-ledtrig.rst.) diff --git a/Documentation/block/blk-ledtrig.rst b/Documentation/block/blk-ledtrig.rst new file mode 100644 index 000000000000..194fc6a51019 --- /dev/null +++ b/Documentation/block/blk-ledtrig.rst @@ -0,0 +1,79 @@ +.. SPDX-License-Identifier: GPL-2.0 + +================================= +Block Device (blkdev) LED Trigger +================================= + +Available when ``CONFIG_BLK_LED_TRIGGERS=y``. + +See also: + +* ``Documentation/ABI/testing/sysfs-class-led-trigger-blkdev`` +* ``Documentation/ABI/testing/sysfs-block`` (``/sys/block/<disk>/led``) + +.. note:: + The examples below use ``<LED>`` to refer to the name of a + system-specific LED. If no suitable LED is available on a test + system (in a virtual machine, for example), it is possible to + use a userspace LED (``Documentation/leds/uleds.rst``). + +Associate the LED with the ``blkdev`` LED trigger:: + + # echo blkdev > /sys/class/leds/<LED>/trigger + + # cat /sys/class/leds/<LED>/trigger + ... kbd-ctrlrlock [blkdev] disk-activity ... + +Note that the ``blink_on`` and ``blink_off`` attributes have been added to the +LED, along with the ``block_devices`` subdirectory. + +The LED is now available for association with block devices:: + + # cat /sys/block/sda/led + [none] <LED> + +Associate the LED with the block device:: + + # echo <LED> > /sys/block/sda/led + + # cat /sys/block/sda/led + none [<LED>] + +Reads and write activity on the device should cause the LED to blink. The +duration of each blink (in milliseconds) can be adjusted by setting +``/sys/class/leds/<LED>/blink_on``, and the minimum delay between blinks can +be set via ``/sys/class/leds/<LED>/blink_off``. + +Associate a second device with the LED:: + + # echo <LED> > /sys/block/sdb/led + + # cat /sys/block/sdb/led + none [<LED>] + +Note that both block devices are linked from the LED's ``block_devices`` +subdirectory:: + + # ls /sys/class/leds/<LED>/block_devices + sda sdb + +Other notes: + +* Many types of block devices work with this trigger, including: + + * SCSI (including SATA and USB) hard disk drives and SSDs + * SCSI (including SATA and USB) optical drives + * SD cards + * loopback block devices (``/dev/loop*``) + +* NVMe SSDs and most virtual block devices can be associated with LEDs, but + they will produce little or no LED activity. + +* Multiple LEDs can be associated with the ``blkdev`` trigger; different block + devices can be associated with different LEDs. + +* This trigger causes associated LED(s) to blink (per the LED's ``blink_on`` + and ``blink_off`` attributes) when a request is sent to an associated + block device's low-level driver. It does not track the duration (or + result) of requests further. Thus, it provides an approximate visual + indication of device activity, not an exact measurement. diff --git a/Documentation/block/index.rst b/Documentation/block/index.rst index 86dcf7159f99..cbb11a42f825 100644 --- a/Documentation/block/index.rst +++ b/Documentation/block/index.rst @@ -25,3 +25,4 @@ Block stat switching-sched writeback_cache_control + blk-ledtrig -- 2.31.1