From patchwork Thu Sep 15 20:50:17 2022 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: Ian Pilcher X-Patchwork-Id: 607098 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 E7087ECAAA1 for ; Thu, 15 Sep 2022 20:50:24 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S229688AbiIOUuX (ORCPT ); Thu, 15 Sep 2022 16:50:23 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:43716 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S229704AbiIOUuV (ORCPT ); Thu, 15 Sep 2022 16:50:21 -0400 Received: from mail-oi1-x236.google.com (mail-oi1-x236.google.com [IPv6:2607:f8b0:4864:20::236]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id ADD343F315 for ; Thu, 15 Sep 2022 13:50:20 -0700 (PDT) Received: by mail-oi1-x236.google.com with SMTP id n83so3734282oif.11 for ; Thu, 15 Sep 2022 13:50:20 -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=0R9xOtzHMvSYAM4ALqi0ekT4KR94SL4j8I+EzvvHIQg=; b=qZxli4KJ0/KpTRCUDwbGfLhbBi78x2YNHCsa6WSAANobdR1p8y2zLGNzpvCqyRj8Om 1soYL6rNanYX4Gh36RoTEGSr9ZE6uBTxDWjLlJkRdcPObj5XGK1ii4Dfd7P2UhlgsKG2 DK6yumglQpqjEo9o8Fr/necdUvdRE4jHYHFqZdDN/hozPtK+6MAgoQwoq8Z8oY7Ltd2D n+WHgrQ249Sk4Ak1vZLH2rQhz69RcUtnkUD/03RDso6G/S/BQWOJbYQN7EZizCWyKLkm HkGhGekNcjyVXkwT9IAu+nhgtwWXIJRmTHY8w+9NeKGqwZCN/It9qp9KV2sERhvp7oYB 3LfQ== 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=0R9xOtzHMvSYAM4ALqi0ekT4KR94SL4j8I+EzvvHIQg=; b=j8VffIvSBUknafXMJF5wwI3QFUDBl8g+Kyu9ixtANT2F5d9fFpXUmwvNTlqiXdG+di 5MbD4jfdnRZIw19n0G1qsCpYuiEgUEOQNzaUEWfBGI6tTK/9ye7XDoPO74cno/r6epnn qIGh90BArtQq3V+bjQQa4q55oQRuM4dY+773LLUL7IBtw6MSsPy82j5JrZnVG3Mus/EF z+9UmrRdHAEosqckS8/jOYyC4n0+BJ+H9fRjqDrm82E/Igbc2IBxbJuheqxAWn8r4hDw a2d9mnriaiW4ulCyHTHJw+3ibiJrdeOK/PcuzjIdoMReC0ykEyr05oZIE+yK6M9wRKWI VhSg== X-Gm-Message-State: ACrzQf1Fg0J3WnFbeup06DkwaDwJf7BrDXdcrcN3sN5ODuGs6ZabtBzI DOQqKDa2hrUllGX5E5LfMDw= X-Google-Smtp-Source: AMsMyM6HV1Zfozav94smtvv/hKopNmzsOlSRbUyCadj5bJZ3JpMo09MjLWA1WmGQ42RiOJPoW9cvGg== X-Received: by 2002:a05:6808:1529:b0:350:2872:4077 with SMTP id u41-20020a056808152900b0035028724077mr856363oiw.41.1663275019862; Thu, 15 Sep 2022 13:50:19 -0700 (PDT) Received: from ian.penurio.us ([47.184.52.85]) by smtp.gmail.com with ESMTPSA id l14-20020a056830054e00b00655dda40f54sm6866882otb.78.2022.09.15.13.50.19 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Thu, 15 Sep 2022 13:50:19 -0700 (PDT) From: Ian Pilcher To: pavel@ucw.cz Cc: linux-leds@vger.kernel.org, kabel@kernel.org, lee.jones@linaro.org Subject: [PATCH v11 1/2] docs: Add block device (blkdev) LED trigger documentation Date: Thu, 15 Sep 2022 15:50:17 -0500 Message-Id: <20220915205018.447014-2-arequipeno@gmail.com> X-Mailer: git-send-email 2.37.3 In-Reply-To: <20220915205018.447014-1-arequipeno@gmail.com> References: <20220915205018.447014-1-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//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 | 68 ++++++++ Documentation/leds/index.rst | 1 + Documentation/leds/ledtrig-blkdev.rst | 155 ++++++++++++++++++ 4 files changed, 234 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..d11d04d804fe 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: September 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..d8d403569b21 --- /dev/null +++ b/Documentation/ABI/testing/sysfs-class-led-trigger-blkdev @@ -0,0 +1,68 @@ +What: /sys/class/leds//blink_time +Date: September 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: September 2022 +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: September 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: September 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: September 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: September 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: September 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: September 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//linked_devices +Date: September 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..c21d1cf66162 --- /dev/null +++ b/Documentation/leds/ledtrig-blkdev.rst @@ -0,0 +1,155 @@ +.. 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`` and ``unlink_dev_by_path`` 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_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``). + +* 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.