From patchwork Mon Sep 26 16:25:02 2022 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: Ian Pilcher X-Patchwork-Id: 609509 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by smtp.lore.kernel.org (Postfix) with ESMTP id 77BD6C32771 for ; Mon, 26 Sep 2022 17:13:57 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S230191AbiIZRN4 (ORCPT ); Mon, 26 Sep 2022 13:13:56 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:50302 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S230344AbiIZRNi (ORCPT ); Mon, 26 Sep 2022 13:13:38 -0400 Received: from mail-oa1-x34.google.com (mail-oa1-x34.google.com [IPv6:2001:4860:4864:20::34]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id 3A8B32C65F; Mon, 26 Sep 2022 09:25:07 -0700 (PDT) Received: by mail-oa1-x34.google.com with SMTP id 586e51a60fabf-12803ac8113so9907760fac.8; Mon, 26 Sep 2022 09:25:07 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=gmail.com; s=20210112; h=content-transfer-encoding:mime-version:references:in-reply-to :message-id:date:subject:cc:to:from:from:to:cc:subject:date; bh=kv5pLuppf3Jboc0nPEbTk92/XrIUrH3iSpM0s9qu3m0=; b=jeLhtYiej8UHVnbavpph9cCYqFRvLXK6HNzBi4JL+8w73mvbvVosEOx7MYxoSTo6Fd Rraiox1S0yoKt7AT0/ZG2AD7+KMKm7gEU6be1jaKLWhMqZy4VveTy0aEexAqN79E2O9R YzX/D3Jusa+1plPiCdLucm6PQjTXW1qZyOn7aQwLYJLFv9dbJEqVsqK+onpvgFF+32XL EPAVLo7tT5biKdw5YZM4JqRXmICDeRVTthvQOcGut/CicjvKia6tAvUDN+bgcZ/CW30s Bp+wKf2aU9R5xEgEkKU6q56GvY25XLPJSqr4V202FWPbf+s45LwhPR2y9WEBnvjyXYAE g2VQ== X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20210112; h=content-transfer-encoding:mime-version:references:in-reply-to :message-id:date:subject:cc:to:from:x-gm-message-state:from:to:cc :subject:date; bh=kv5pLuppf3Jboc0nPEbTk92/XrIUrH3iSpM0s9qu3m0=; b=fnKBsWb/568/fVe7g881QTUJInxts9A/k5ei3I8j6eDstD5ey3fL1TnTZRWtiXzpDn lpzngcU6TrfbQ21PdhObAqZ52xXsDc/acC2kbKE/a1N8GAgpy37vSxlqOBrIo5p+y5as 0tVjYMNPLyhTfZqnH6aMlS6yV3iQW3CYxwqxIPJ+X82lE34QcTTCWXI6pLCivP01Z9kW Qybiy28PhkAbHNvYwu1frq3Kwq/yn4+QopSuP0aiNU86EvEhIFcKBWq9eyO7Glo+OomZ m5Okk5QwwDtF1k5CHPXvCEg1EuQZ92tgObrF+AgOKkyKgkOWMp1lsiYANOtuH+Hi9sVl Li+A== X-Gm-Message-State: ACrzQf07squhIB0cRXBj+a+1ppYcmbHLJkT4rGBoefu/ZsQnCupFNVia czuXJLSTlLM8G27g4pDhtZ0= X-Google-Smtp-Source: AMsMyM7dK2sXVm+pfzvhBERbQsT6zZ9QpmA86kv1qUubXGxHLYe5W0W3xzA7J0gBkQIX9QDNY6hjYA== X-Received: by 2002:a05:6870:d1c9:b0:127:2df9:b459 with SMTP id b9-20020a056870d1c900b001272df9b459mr19557160oac.168.1664209506408; Mon, 26 Sep 2022 09:25:06 -0700 (PDT) Received: from ian.penurio.us ([47.184.52.85]) by smtp.gmail.com with ESMTPSA id k7-20020a4ab287000000b004762a830156sm6789097ooo.32.2022.09.26.09.25.05 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Mon, 26 Sep 2022 09:25:05 -0700 (PDT) From: Ian Pilcher To: pavel@ucw.cz Cc: linux-leds@vger.kernel.org, linux-kernel@vger.kernel.org, kabel@kernel.org, torvic9@mailbox.org Subject: [PATCH v12 1/2] docs: Add block device (blkdev) LED trigger documentation Date: Mon, 26 Sep 2022 11:25:02 -0500 Message-Id: <20220926162503.451320-2-arequipeno@gmail.com> X-Mailer: git-send-email 2.37.3 In-Reply-To: <20220926162503.451320-1-arequipeno@gmail.com> References: <20220926162503.451320-1-arequipeno@gmail.com> MIME-Version: 1.0 Precedence: bulk List-ID: X-Mailing-List: linux-leds@vger.kernel.org Add Documentation/ABI/testing/sysfs-class-led-trigger-blkdev to document: * /sys/class/leds//blink_time * /sys/class/leds//check_interval * /sys/class/leds//blink_on_{read,write,discard,flush} * /sys/class/leds//link_dev_by_path * /sys/class/leds//unlink_dev_by_path * /sys/class/leds//unlink_dev_by_name * /sys/class/leds//linked_devices Add /sys/block//linked_leds to Documentation/ABI/stable/sysfs-block. Add overview in Documentation/leds/ledtrig-blkdev.rst. Signed-off-by: Ian Pilcher --- Documentation/ABI/stable/sysfs-block | 10 ++ .../testing/sysfs-class-led-trigger-blkdev | 78 +++++++++ Documentation/leds/index.rst | 1 + Documentation/leds/ledtrig-blkdev.rst | 158 ++++++++++++++++++ 4 files changed, 247 insertions(+) create mode 100644 Documentation/ABI/testing/sysfs-class-led-trigger-blkdev create mode 100644 Documentation/leds/ledtrig-blkdev.rst diff --git a/Documentation/ABI/stable/sysfs-block b/Documentation/ABI/stable/sysfs-block index cd14ecb3c9a5..853cb2601242 100644 --- a/Documentation/ABI/stable/sysfs-block +++ b/Documentation/ABI/stable/sysfs-block @@ -101,6 +101,16 @@ Description: devices that support receiving integrity metadata. +What: /sys/block//linked_leds +Date: October 2022 +Contact: Ian Pilcher +Description: + Directory that contains symbolic links to all LEDs that + are associated with (linked to) this block device by the + blkdev LED trigger. Only present when at least one LED + is linked. (See Documentation/leds/ledtrig-blkdev.rst.) + + What: /sys/block///alignment_offset Date: April 2009 Contact: Martin K. Petersen 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..45275eb0bad3 --- /dev/null +++ b/Documentation/ABI/testing/sysfs-class-led-trigger-blkdev @@ -0,0 +1,78 @@ +What: /sys/class/leds//blink_time +Date: October 2022 +Contact: Ian Pilcher +Description: + Time (in milliseconds) that the LED will be on during a single + "blink". + +What: /sys/class/leds//check_interval +Date: October 2022 +Contact: Ian Pilcher +Description: + Interval (in milliseconds) between checks of the block devices + linked to this LED. The LED will be blinked if the correct type + of activity (see blink_on_{read,write,discard,flush} attributes) + has occurred on any of the linked devices since the previous + check. + +What: /sys/class/leds//blink_on_read +Date: October 2022 +Contact: Ian Pilcher +Description: + Boolean that determines whether the LED will blink in response + to read activity on any of its linked block devices. + +What: /sys/class/leds//blink_on_write +Date: October 2022 +Contact: Ian Pilcher +Description: + Boolean that determines whether the LED will blink in response + to write activity on any of its linked block devices. + +What: /sys/class/leds//blink_on_discard +Date: October 2022 +Contact: Ian Pilcher +Description: + Boolean that determines whether the LED will blink in response + to discard activity on any of its linked block devices. + +What: /sys/class/leds//blink_on_flush +Date: October 2022 +Contact: Ian Pilcher +Description: + Boolean that determines whether the LED will blink in response + to cache flush activity on any of its linked block devices. + +What: /sys/class/leds//link_dev_by_path +Date: October 2022 +Contact: Ian Pilcher +Description: + Associate a block device with this LED by writing the path to + the device special file (e.g. /dev/sda) to this attribute. + Symbolic links are followed. + +What: /sys/class/leds//unlink_dev_by_path +Date: October 2022 +Contact: Ian Pilcher +Description: + Remove the association between this LED and a block device by + writing the path to the device special file (e.g. /dev/sda) to + this attribute. Symbolic links are followed. + +What: /sys/class/leds//unlink_dev_by_name +Date: October 2022 +Contact: Ian Pilcher +Description: + Remove the association between this LED and a block device by + writing the kernel name of the device (e.g. sda) to this + attribute. + +What: /sys/class/leds//linked_devices +Date: October 2022 +Contact: Ian Pilcher +Description: + Directory containing links to all block devices that are + associated with this LED. (Note that the names of the + symbolic links in this directory are *kernel* names, which + may not match the device special file paths written to + link_device and unlink_device.) diff --git a/Documentation/leds/index.rst b/Documentation/leds/index.rst index e5d63b940045..e3c24e468cbc 100644 --- a/Documentation/leds/index.rst +++ b/Documentation/leds/index.rst @@ -10,6 +10,7 @@ LEDs leds-class leds-class-flash leds-class-multicolor + ledtrig-blkdev ledtrig-oneshot ledtrig-transient ledtrig-usbport diff --git a/Documentation/leds/ledtrig-blkdev.rst b/Documentation/leds/ledtrig-blkdev.rst new file mode 100644 index 000000000000..9ff5b99de451 --- /dev/null +++ b/Documentation/leds/ledtrig-blkdev.rst @@ -0,0 +1,158 @@ +.. SPDX-License-Identifier: GPL-2.0 + +================================= +Block Device (blkdev) LED Trigger +================================= + +Available when ``CONFIG_LEDS_TRIGGER_BLKDEV=y`` or +``CONFIG_LEDS_TRIGGER_BLKDEV=m``. + +See also: + +* ``Documentation/ABI/testing/sysfs-class-led-trigger-blkdev`` +* ``Documentation/ABI/stable/sysfs-block`` (``/sys/block//linked_leds``) + +Overview +======== + +.. note:: + The examples below use ```` 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. (See ``Documentation/leds/uleds.rst``.) + +Verify that the ``blkdev`` LED trigger is available:: + + # grep blkdev /sys/class/leds//trigger + ... rfkill-none blkdev + +(If the previous command produces no output, you may need to load the trigger +module - ``modprobe ledtrig_blkdev``. If the module is not available, check +the value of ``CONFIG_LEDS_TRIGGER_BLKDEV`` in your kernel configuration.) + +Associate the LED with the ``blkdev`` LED trigger:: + + # echo blkdev > /sys/class/leds//trigger + + # cat /sys/class/leds//trigger + ... rfkill-none [blkdev] + +Note that several new device attributes are available in the +``/sys/class/leds/`` directory. + +* ``link_dev_by_path``, ``unlink_dev_by_path``, and ``unlink_dev_by_name`` are + used to manage the set of block devices associated with this LED. The LED + will blink when activity occurs on any of its linked devices. + +* ``blink_on_read``, ``blink_on_write``, ``blink_on_discard``, and + ``blink_on_flush`` are boolean values that determine whether the LED will + blink when a particular type of activity is detected on one of its linked + block devices. + +* ``blink_time`` is the duration (in milliseconds) of each blink of this LED. + (The minimum value is 10 milliseconds.) + +* ``check_interval`` is the frequency (in milliseconds) with which block devices + linked to this LED will be checked for activity and the LED blinked (if the + correct type of activity has occurred). + +* The ``linked_devices`` directory will contain a symbolic link to every device + that is associated with this LED. + +Link a block device to the LED:: + + # echo /dev/sda > /sys/class/leds//link_dev_by_path + + # ls /sys/class/leds//linked_devices + sda + +(The value written to ``link_dev_by_path`` must be the path of the device +special file, such as ``/dev/sda``, that represents the block device - or the +path of a symbolic link to such a device special file.) + +Activity on the device will now cause the LED to blink. The duration of each +blink (in milliseconds) can be adjusted by setting +``/sys/class/leds//blink_time``. (But see **check_interval and +blink_time** below.) + +Associate a second device with the LED:: + + # echo /dev/sdb > /sys/class/leds//link_dev_by_path + + # ls /sys/class/leds//linked_devices + sda sdb + +When a block device is linked to one or more LEDs, the LEDs are linked from +the device's ``linked_leds`` directory:: + + # ls /sys/class/block/sd{a,b}/linked_leds + /sys/class/block/sda/linked_leds: + + + /sys/class/block/sdb/linked_leds: + + +(The ``linked_leds`` directory only exists when the block device is linked to +at least one LED.) + +``check_interval`` and ``blink_time`` +===================================== + +* By default, linked block devices are checked for activity every 100 + milliseconds. This frequency can be changed for an LED via the + ``/sys/class/leds//check_interval`` attribute. (The minimum value is 25 + milliseconds.) + +* All block devices associated with an LED are checked for activity every + ``check_interval`` milliseconds, and a blink is triggered if the correct type + of activity (as determined by the LED's ``blink_on_*`` attributes) is + detected. The duration of an LED's blink is determined by its ``blink_time`` + attribute. Thus (when the correct type of activity is detected), the LED will + be on for ``blink_time`` milliseconds and off for + ``check_interval - blink_time`` milliseconds. + +* The LED subsystem ignores new blink requests for an LED that is already in + in the process of blinking, so setting a ``blink_time`` greater than or equal + to ``check_interval`` will cause some blinks to be missed. + +* Because of processing times, scheduling latencies, etc., avoiding missed + blinks actually requires a difference of at least a few milliseconds between + the ``blink_time`` and ``check_interval``. The required difference is likely + to vary from system to system. As a reference, a Thecus N5550 NAS requires a + difference of 7 milliseconds (e.g. ``check_interval == 100``, + ``blink_time == 93``). + +* The default values (``check_interval == 100``, ``blink_time == 75``) cause the + LED associated with a continuously active device to blink rapidly. For a more + "always on" effect, increase the ``blink_time`` (but not too much; see the + previous bullet). + +Other Notes +=========== + +* Many (possibly all) 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 + * NVMe SSDs + * SD cards + * loopback block devices (``/dev/loop*``) + * device mapper devices, such as LVM logical volumes + * MD RAID devices + * zRAM compressed RAM-disks + * partitions on block devices that support them + +* The names of the symbolic links in ``/sys/class/leds//linked_devices`` + are **kernel** names, which may not match the paths used for + ``link_dev_by_path`` and ``unlink_dev_by_path``. This is most likely when a + symbolic link is used to refer to the device (as is common with logical + volumes), but it can be true for any device, because nothing prevents the + creation of device special files with arbitrary names (e.g. + ``sudo mknod /foo b 8 0``). + + Kernel names can be used to unlink block devices from LEDs by writing them to + the LED's ``unlink_dev_by_name`` attribute. + +* The ``blkdev`` LED trigger supports many-to-many device/LED associations. + A device can be associated with multiple LEDs, and an LED can be associated + with multiple devices.