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 X-Spam-Level: X-Spam-Status: No, score=-15.7 required=3.0 tests=BAYES_00,DKIM_SIGNED, DKIM_VALID,DKIM_VALID_AU,FREEMAIL_FORGED_FROMDOMAIN,FREEMAIL_FROM, HEADER_FROM_DIFFERENT_DOMAINS,INCLUDES_CR_TRAILER,INCLUDES_PATCH, MAILING_LIST_MULTI,SPF_HELO_NONE,SPF_PASS,USER_AGENT_GIT autolearn=ham autolearn_force=no version=3.4.0 Received: from mail.kernel.org (mail.kernel.org [198.145.29.99]) by smtp.lore.kernel.org (Postfix) with ESMTP id 816AEC433EF for ; Thu, 16 Sep 2021 20:21:41 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id 53FCE6120F for ; Thu, 16 Sep 2021 20:21:41 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S235165AbhIPUW6 (ORCPT ); Thu, 16 Sep 2021 16:22:58 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:44438 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S233469AbhIPUW6 (ORCPT ); Thu, 16 Sep 2021 16:22:58 -0400 Received: from mail-oo1-xc2f.google.com (mail-oo1-xc2f.google.com [IPv6:2607:f8b0:4864:20::c2f]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id 2CB3EC061756; Thu, 16 Sep 2021 13:21:37 -0700 (PDT) Received: by mail-oo1-xc2f.google.com with SMTP id k20-20020a4ad114000000b0029133123994so2463865oor.4; Thu, 16 Sep 2021 13:21:37 -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=21Ni4S8qL8MMh6tpbE5xDFN+nz1NDcInzGTRf18IUPk=; b=AgJvU59Q1S9HPWgyeLk38bv7MlDznnCbS4F865A3oTjm8yY1jU/q2q9NyXkZWvBgf4 mnr8VmB8SviBbzdg9HQxsC6I/upsIRYPmI6CLnvgWPnv76+2DFC2ImUXc3BIaSzp4GBb 00cA/Ph3KEcdycgLtpDPnrCq5DCnvVhzEIHQrndF8of79WljbiAvQiexZQ90pT3D6sr2 vHnSjHGt20f3uHA+pswV3cEoQXjcsF6h9Cg7UDqRiq9ubba7sORuehpct61yT9ZzBxxM Sfu5ucKFFUmlD3FqRZVaLSmlDNo7Z6zCu2OTsoVoL6OpRgwzOqIIq33qAJgiCq/UE+01 Zmhg== 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=21Ni4S8qL8MMh6tpbE5xDFN+nz1NDcInzGTRf18IUPk=; b=EyojCRCVnpjRIL8dPLWKH786NrNqxPSUyebZ5QQ5MMsuiQ/XL9MR9UFrGWo8D+ikUP KPoyICWo6AqhYTFyidWc5bHstOgie49IRNNG87hZ5YLlgHaJAljfz/yZToF7bW6TK6tw eR5lj1IcAQvgrnKIrhFAwyzmvp93qkZpwJXXSr6oE5yhkWW1BOIwUZP/2PPEgI1LKr/k bviRoOi5XKHJk3faFv4WPKQeuV58ZSow/dCJgEtT0URdC6lNYtVxiZt4JFId79dIDnB1 wNnUJ4jU/FiQRc0iPaRlenp94IrYj1lJ/zN0l6xvNHdaJr1zAo5BQwOcvjutOMxnXOiE yo3g== X-Gm-Message-State: AOAM5327QMHtADlNnGtrgpGZ87QZAXeW2n91pYIi/z80h3Sh0m6S0lpu ajLuJqHBY0iHLIUK1ip4i8WNujRG7ohFjQ== X-Google-Smtp-Source: ABdhPJzo/NUkdbzYaPx3MvN1ZMDr3wNXCSeRM6vKOzWJfltz9CVPOkMg/P6ExcdPsZoiG6yI1Z/bCA== X-Received: by 2002:a4a:4344:: with SMTP id l4mr5934735ooj.38.1631823696437; Thu, 16 Sep 2021 13:21:36 -0700 (PDT) Received: from ian.penurio.us ([47.184.51.90]) by smtp.gmail.com with ESMTPSA id o24sm948057oie.17.2021.09.16.13.21.36 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Thu, 16 Sep 2021 13:21:36 -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 Subject: [PATCH v4 1/2] docs: Add block device (blkdev) LED trigger documentation Date: Thu, 16 Sep 2021 15:21:26 -0500 Message-Id: <20210916202127.1216994-2-arequipeno@gmail.com> X-Mailer: git-send-email 2.31.1 In-Reply-To: <20210916202127.1216994-1-arequipeno@gmail.com> References: <20210916202127.1216994-1-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 | 50 ++++++ Documentation/leds/index.rst | 1 + Documentation/leds/ledtrig-blkdev.rst | 149 ++++++++++++++++++ 4 files changed, 209 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..80d4becc4e6d 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: September 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..b8730d450dbf --- /dev/null +++ b/Documentation/ABI/testing/sysfs-class-led-trigger-blkdev @@ -0,0 +1,50 @@ +What: /sys/class/leds//blink_time +Date: September 2021 +Contact: Ian Pilcher +Description: + Time (in milliseconds) that the LED will be on during a single + "blink". + +What: /sys/class/leds//mode +Date: September 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: September 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. Optionally, the leading "/dev/" + may be omitted. + +What: /sys/class/leds//unlink_device +Date: September 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. Optionally, the + leading "/dev/" may be omitted. + +What: /sys/class/leds//linked_devices +Date: September 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: September 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..af319125ab25 --- /dev/null +++ b/Documentation/leds/ledtrig-blkdev.rst @@ -0,0 +1,149 @@ +.. 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 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. The example above works because it +is possible to omit the leading ``/dev``.) + +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 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 (``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