From mboxrd@z Thu Jan 1 00:00:00 1970 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 mail.kernel.org (mail.kernel.org [198.145.29.99]) by smtp.lore.kernel.org (Postfix) with ESMTP id 4AC36C433EF for ; Mon, 4 Oct 2021 15:56:02 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id 325A661401 for ; Mon, 4 Oct 2021 15:56:02 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S236046AbhJDP5u (ORCPT ); Mon, 4 Oct 2021 11:57:50 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:42002 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S235935AbhJDP5u (ORCPT ); Mon, 4 Oct 2021 11:57:50 -0400 Received: from mail-ot1-x32d.google.com (mail-ot1-x32d.google.com [IPv6:2607:f8b0:4864:20::32d]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id 07A96C061746; Mon, 4 Oct 2021 08:56:01 -0700 (PDT) Received: by mail-ot1-x32d.google.com with SMTP id x33-20020a9d37a4000000b0054733a85462so22077925otb.10; Mon, 04 Oct 2021 08:56:01 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=gmail.com; s=20210112; h=from:to:cc:subject:date:message-id:in-reply-to:references :mime-version:content-transfer-encoding; bh=615yzYUETLAylJ4IzkIwcwgsdamRD+ElmZX6ofxvOfg=; b=VLuuq3UoBtkZ/+3ywXJYaCFBeOYH2Uc+FNGzkC5fazqot7x2S9brDJKVkvIx2kBQ6h 9ybqvWOfDYZdFbOoLd+EqL8vDG9P9JYjlGBZhnQH22d6hdCGddtrSV8GDT1ZKAx+P7uy bMTb70/XtmyJqSIc5HL1k73mbX+BhdgXH/0oaY/kecfEYrdEbEl5F+XU3MdeN2hRUR7a HzaVIVt5hf1NpOuU9wOBGrkNCU6Q4vmriI7CDfX9pi4AicLHvxeCOu0bgkb85pPcBKQQ U4FnzsOQzqSoZKNbFsJvHd/mnzdkcdqVmr5jBrwnP3Wc8W7epsyOiHNOxzgVz6VdNhQk BdyA== X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20210112; h=x-gm-message-state:from:to:cc:subject:date:message-id:in-reply-to :references:mime-version:content-transfer-encoding; bh=615yzYUETLAylJ4IzkIwcwgsdamRD+ElmZX6ofxvOfg=; b=KfuVuro2NpiJdJS/VSly+Ef6+bRxx1giXYDqDYYlwlfOxiWEyZyaxqkoXz3TVAKgqJ x1kuQuH7H80V48NlGs13X9ZfrdegEGHNT4WUeHMQlJ/aP5cXkPkwWXKiNx53w6h6jJzi qC4iOGxLLetoc30fcGxPyDpO2+xAnrn0w73lLKBE5u4qTVUeeIQJKXth4IokD7zsJqkn xQfkRmacgKZnVafKehbxmfi3Gnra69Xl9XRJ2AUTV2hW4mtC1+kll3hngK6X/vn9p2ta 9yfZ+5gR3uvw5flvS+pr8mB5eDovJeitsF+xSMPWvzG+INUOQDIPnZ10wTgP9h56/wh5 ZCsw== X-Gm-Message-State: AOAM530RcSoCxrIemgZTii1vhxrXysRt2T+s98EYgExNg+HKRlQW4z7n 3d2lfF/uue34zn1Smc2FRSQ= X-Google-Smtp-Source: ABdhPJxaqzPbRdiKhxLpJ9t8YrKDyrtcsqq/l6VWqkDVUNhV/LNvJbeE7nB22No9v8MfdswV2vqBpQ== X-Received: by 2002:a9d:468a:: with SMTP id z10mr9555000ote.110.1633362960264; Mon, 04 Oct 2021 08:56:00 -0700 (PDT) Received: from ian.penurio.us ([47.184.51.90]) by smtp.gmail.com with ESMTPSA id p18sm3046878otk.7.2021.10.04.08.55.59 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Mon, 04 Oct 2021 08:56:00 -0700 (PDT) From: Ian Pilcher To: pavel@ucw.cz Cc: linux-leds@vger.kernel.org, linux-kernel@vger.kernel.org, gregkh@linuxfoundation.org, kabel@kernel.org, hch@infradead.org Subject: [RESEND PATCH v5 1/2] docs: Add block device (blkdev) LED trigger documentation Date: Mon, 4 Oct 2021 10:55:45 -0500 Message-Id: <20211004155546.1120869-2-arequipeno@gmail.com> X-Mailer: git-send-email 2.31.1 In-Reply-To: <20211004155546.1120869-1-arequipeno@gmail.com> References: <20211004155546.1120869-1-arequipeno@gmail.com> MIME-Version: 1.0 Content-Transfer-Encoding: 8bit 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//mode * /sys/class/leds//link_device * /sys/class/leds//unlink_device * /sys/class/leds//linked_devices * /sys/class/ledtrig_blkdev/interval Add /sys/block//linked_leds to Documentation/ABI/testing/sysfs-block. Add overview in Documentation/leds/ledtrig-blkdev.rst. Signed-off-by: Ian Pilcher --- Documentation/ABI/testing/sysfs-block | 9 ++ .../testing/sysfs-class-led-trigger-blkdev | 48 ++++++ Documentation/leds/index.rst | 1 + Documentation/leds/ledtrig-blkdev.rst | 148 ++++++++++++++++++ 4 files changed, 206 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/testing/sysfs-block b/Documentation/ABI/testing/sysfs-block index a0ed87386639..26931894084b 100644 --- a/Documentation/ABI/testing/sysfs-block +++ b/Documentation/ABI/testing/sysfs-block @@ -328,3 +328,12 @@ 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//linked_leds +Date: October 2021 +Contact: Ian Pilcher +Description: + Directory containing links to all LEDs that are associated + with this block device through the blkdev LED trigger. Only + present when at least one LED is associated. (See + Documentation/leds/ledtrig-blkdev.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..292c581e2cda --- /dev/null +++ b/Documentation/ABI/testing/sysfs-class-led-trigger-blkdev @@ -0,0 +1,48 @@ +What: /sys/class/leds//blink_time +Date: October 2021 +Contact: Ian Pilcher +Description: + Time (in milliseconds) that the LED will be on during a single + "blink". + +What: /sys/class/leds//mode +Date: October 2021 +Contact: Ian Pilcher +Description: + Type of events for which LED will blink - read, write, + or rw (both). Note that any activity that changes the state of + the device's non-volatile storage (including discards and cache + flushes) is considered to be a write. + +What: /sys/class/leds//link_device +Date: October 2021 +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_device +Date: October 2021 +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//linked_devices +Date: October 2021 +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.) + +What: /sys/class/ledtrig_blkdev/interval +Date: October 2021 +Contact: Ian Pilcher +Description: + Frequency (in milliseconds) with which block devices associated + with the blkdev LED trigger will be checked for activity. 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..5be141add33f --- /dev/null +++ b/Documentation/leds/ledtrig-blkdev.rst @@ -0,0 +1,148 @@ +.. 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/testing/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_device`` and ``unlink_device`` are used to manage the set of block + devices associated with this LED. The LED will blink in response to read or + write activity on its linked devices. + +* ``mode`` is used to control the type of device activity that will cause this + LED to blink - read activity, write activity, or both. (Note that any + activity that changes the state of a device's non-volatile storage is + considered to be a write. This includes discard and cache flush requests.) + +* ``blink_time`` is the duration (in milliseconds) of each blink of this LED. + (The minimum value is 10 milliseconds.) + +* 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_device + + # ls /sys/class/leds//linked_devices + sda + +(The value written to ``link_device`` 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.) + +Read 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//blink_time``. (But see **interval and blink_time** +below.) + +Associate a second device with the LED:: + + # echo /dev/sdb > /sys/class/leds//link_device + + # 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.) + +``interval`` and ``blink_time`` +=============================== + +* By default, linked block devices are checked for activity every 100 + milliseconds. This frequency can be changed via the + ``/sys/class/ledtrig_blkdev/interval`` attribute. (The minimum value is 25 + milliseconds.) + +* All associated devices are checked for activity every ``interval`` + milliseconds, and a blink is triggered on appropriate LEDs. The duration + of an LED's blink is determined by its ``blink_time`` attribute. Thus + (assuming that activity of the relevant type has occurred on one of an LED's + linked devices), the LED will be on for ``blink_time`` milliseconds and off + for ``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 ``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 ``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 (``interval == 100``, ``blink_time == 93``). + +* The default values (``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 devics 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_device`` and ``unlink_device``. 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``). + +* 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. -- 2.31.1