From patchwork Fri Nov 19 21:27:32 2021 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: Ian Pilcher X-Patchwork-Id: 517305 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 21115C433EF for ; Fri, 19 Nov 2021 21:27:45 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S235461AbhKSVaq (ORCPT ); Fri, 19 Nov 2021 16:30:46 -0500 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:41614 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S232958AbhKSVaq (ORCPT ); Fri, 19 Nov 2021 16:30:46 -0500 Received: from mail-ot1-x332.google.com (mail-ot1-x332.google.com [IPv6:2607:f8b0:4864:20::332]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id 0D30BC061574; Fri, 19 Nov 2021 13:27:44 -0800 (PST) Received: by mail-ot1-x332.google.com with SMTP id a23-20020a9d4717000000b0056c15d6d0caso18640346otf.12; Fri, 19 Nov 2021 13:27:44 -0800 (PST) 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=IEW9wZzlX3HIR8TEI5xtnLyQsghS8GAsGDuxZ7c+C24=; b=EXMWa/0Rm3ixaRy+kZjg9QDNYBZVSu/DJTMdKbX8ewaFkU9AOzpSMXL2WrOYACMpvQ GZnukrZOEIpIwO8MQqTST9I/ouDB4G+5hFUCUzkzqVuEEkg2oWV5d8MQBkgeQObJ/ATD dtVEBkz8zlOyx1XB8eIRCQZJ1EdZ/cknrowtR/FBRcJ/moFljhxe/vJs0wafJ6ERKUHZ 1Kavde3uGJteL25w8DueUR0i7+GYJM4eDupdDwoDHOeyXXvSyJL2q0EtbfNBPfT32W0N F/tdRoYjoInKnL2k+BwsfJxFrtULwMLT46jtvD1pw3fNapa4VSQabnJ5bMC6eWRzYzeA iRuw== 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=IEW9wZzlX3HIR8TEI5xtnLyQsghS8GAsGDuxZ7c+C24=; b=y/ui7LlWUc3f1kQki6++gUUm9I6crZGtv/wCE58k5hveVG3quxCz3dCGfSxLhRWidG XJNFJa21o8rXwkQW/rNFADlXt6/6KmaHSlEQvfjbriqZBJu9/scUxls2/G8ENHYS1ldP wpWvNomClK2L/kLKbcy5GBdao7xEo795HKhXIKbdagoWJvJdv+Yl7CcV1Mnv+d9aZikr c6Wnb46Naf8/NMMKhgK2rbo5vgeEGLPrrKTeUQ8omCaQVUJblq6y+8EQdd4MKELIWYB5 IpkBq+PtulwWjK1ZdhUqBn80tn6/KxdmuY1EQneuHhuaSuQc7UO6Iy3IdDu/p09Iwd4b PSwg== X-Gm-Message-State: AOAM531hvkUoER6/tsCKiAZeT4nA4qY9NAMjWVXbvsZX2Dbjs5RCOw79 /RhZdhjHyvipllOhreXD0p8= X-Google-Smtp-Source: ABdhPJyUwy7y+sGLNxQV7Tud4DwKMP3TZ4IOAeCaYbtZ/3F3SeCtELmRqFuKv4xc4YdbYQgtGO7tEg== X-Received: by 2002:a9d:7586:: with SMTP id s6mr7345553otk.158.1637357263258; Fri, 19 Nov 2021 13:27:43 -0800 (PST) Received: from ian.penurio.us ([47.184.51.90]) by smtp.gmail.com with ESMTPSA id w29sm233936ooe.25.2021.11.19.13.27.42 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Fri, 19 Nov 2021 13:27:43 -0800 (PST) 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: [RESEND PATCH v8 1/2] docs: Add block device (blkdev) LED trigger documentation Date: Fri, 19 Nov 2021 15:27:32 -0600 Message-Id: <20211119212733.286427-2-arequipeno@gmail.com> X-Mailer: git-send-email 2.33.1 In-Reply-To: <20211119212733.286427-1-arequipeno@gmail.com> References: <20211119212733.286427-1-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_device * /sys/class/leds//unlink_device * /sys/class/leds//linked_devices 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 | 68 ++++++++ Documentation/leds/index.rst | 1 + Documentation/leds/ledtrig-blkdev.rst | 154 ++++++++++++++++++ 4 files changed, 232 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 b16b0c45a272..dd9b1589c1a2 100644 --- a/Documentation/ABI/testing/sysfs-block +++ b/Documentation/ABI/testing/sysfs-block @@ -344,3 +344,12 @@ 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: November 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..4cb9920c0d32 --- /dev/null +++ b/Documentation/ABI/testing/sysfs-class-led-trigger-blkdev @@ -0,0 +1,68 @@ +What: /sys/class/leds//blink_time +Date: November 2021 +Contact: Ian Pilcher +Description: + Time (in milliseconds) that the LED will be on during a single + "blink". + +What: /sys/class/leds//check_interval +Date: November 2021 +Contact: Ian Pilcher +Description: + Frequency (in milliseconds) with which block devices linked to + this LED will be checked for activity and the LED will + (potentially) be blinked. + +What: /sys/class/leds//blink_on_read +Date: November 2021 +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: November 2021 +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: November 2021 +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: November 2021 +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_device +Date: November 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: November 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: November 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.) 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..14b598bb07e9 --- /dev/null +++ b/Documentation/leds/ledtrig-blkdev.rst @@ -0,0 +1,154 @@ +.. 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. + +* ``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_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.) + +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 **check_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.) + +``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 (``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 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.