From 9d77db3c730780c8ef5ccd4b66403ff5675cfe4e Mon Sep 17 00:00:00 2001 From: hc <hc@nodka.com> Date: Mon, 13 May 2024 10:30:14 +0000 Subject: [PATCH] modify sin led gpio --- kernel/Documentation/trace/stm.rst | 42 +++++++++++++++++++++++++++++++----------- 1 files changed, 31 insertions(+), 11 deletions(-) diff --git a/kernel/Documentation/trace/stm.rst b/kernel/Documentation/trace/stm.rst index 2c22ddb..1ed49dd 100644 --- a/kernel/Documentation/trace/stm.rst +++ b/kernel/Documentation/trace/stm.rst @@ -1,3 +1,5 @@ +.. SPDX-License-Identifier: GPL-2.0 + =================== System Trace Module =================== @@ -31,8 +33,8 @@ have a name (string identifier) and a range of masters and channels associated with it, located in "stp-policy" subsystem directory in configfs. The topmost directory's name (the policy) is formatted as -the STM device name to which this policy applies and and arbitrary -string identifier separated by a stop. From the examle above, a rule +the STM device name to which this policy applies and an arbitrary +string identifier separated by a stop. From the example above, a rule may look like this:: $ ls /config/stp-policy/dummy_stm.my-policy/user @@ -53,12 +55,30 @@ be used for trace sources with the id string of "user/dummy". Trace sources have to open the stm class device's node and write their -trace data into its file descriptor. In order to identify themselves -to the policy, they need to do a STP_POLICY_ID_SET ioctl on this file -descriptor providing their id string. Otherwise, they will be -automatically allocated a master/channel pair upon first write to this -file descriptor according to the "default" rule of the policy, if such -exists. +trace data into its file descriptor. + +In order to find an appropriate policy node for a given trace source, +several mechanisms can be used. First, a trace source can explicitly +identify itself by calling an STP_POLICY_ID_SET ioctl on the character +device's file descriptor, providing their id string, before they write +any data there. Secondly, if they chose not to perform the explicit +identification (because you may not want to patch existing software +to do this), they can just start writing the data, at which point the +stm core will try to find a policy node with the name matching the +task's name (e.g., "syslogd") and if one exists, it will be used. +Thirdly, if the task name can't be found among the policy nodes, the +catch-all entry "default" will be used, if it exists. This entry also +needs to be created and configured by the system administrator or +whatever tools are taking care of the policy configuration. Finally, +if all the above steps failed, the write() to an stm file descriptor +will return a error (EINVAL). + +Previously, if no policy nodes were found for a trace source, the stm +class would silently fall back to allocating the first available +contiguous range of master/channels from the beginning of the device's +master/channel range. The new requirement for a policy node to exist +will help programmers and sysadmins identify gaps in configuration +and have better control over the un-identified sources. Some STM devices may allow direct mapping of the channel mmio regions to userspace for zero-copy writing. One mappable page (in terms of @@ -92,9 +112,9 @@ there's a node in the root of the policy directory that matches the stm_source device's name (for example, "console"), this node will be used to allocate master and channel numbers. If there's no such policy -node, the stm core will pick the first contiguous chunk of channels -within the first available master. Note that the node must exist -before the stm_source device is connected to its stm device. +node, the stm core will use the catch-all entry "default", if one +exists. If neither policy nodes exist, the write() to stm_source_link +will return an error. stm_console =========== -- Gitblit v1.6.2