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=-8.8 required=3.0 tests=HEADER_FROM_DIFFERENT_DOMAINS, INCLUDES_PATCH,MAILING_LIST_MULTI,SIGNED_OFF_BY,SPF_PASS,URIBL_BLOCKED, 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 4E9F1C00449 for ; Fri, 5 Oct 2018 12:44:07 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id 1D14B2087D for ; Fri, 5 Oct 2018 12:44:07 +0000 (UTC) DMARC-Filter: OpenDMARC Filter v1.3.2 mail.kernel.org 1D14B2087D Authentication-Results: mail.kernel.org; dmarc=fail (p=none dis=none) header.from=linux.intel.com Authentication-Results: mail.kernel.org; spf=none smtp.mailfrom=linux-kernel-owner@vger.kernel.org Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1728812AbeJETmj (ORCPT ); Fri, 5 Oct 2018 15:42:39 -0400 Received: from mga09.intel.com ([134.134.136.24]:28570 "EHLO mga09.intel.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1728687AbeJETmQ (ORCPT ); Fri, 5 Oct 2018 15:42:16 -0400 X-Amp-Result: SKIPPED(no attachment in message) X-Amp-File-Uploaded: False Received: from orsmga002.jf.intel.com ([10.7.209.21]) by orsmga102.jf.intel.com with ESMTP/TLS/DHE-RSA-AES256-GCM-SHA384; 05 Oct 2018 05:43:40 -0700 X-ExtLoop1: 1 X-IronPort-AV: E=Sophos;i="5.54,344,1534834800"; d="scan'208";a="97687814" Received: from black.fi.intel.com (HELO black.fi.intel.com.) ([10.237.72.28]) by orsmga002.jf.intel.com with ESMTP; 05 Oct 2018 05:43:33 -0700 From: Alexander Shishkin To: Greg Kroah-Hartman Cc: Mathieu Poirier , linux-kernel@vger.kernel.org, Alexander Shishkin Subject: [GIT PULL 12/16] stm class: Update documentation to match the new identification rules Date: Fri, 5 Oct 2018 15:43:02 +0300 Message-Id: <20181005124306.54870-13-alexander.shishkin@linux.intel.com> X-Mailer: git-send-email 2.19.0 In-Reply-To: <20181005124306.54870-1-alexander.shishkin@linux.intel.com> References: <20181005124306.54870-1-alexander.shishkin@linux.intel.com> MIME-Version: 1.0 Content-Transfer-Encoding: 8bit Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org The rules and order of identification of trace sources against the "stp-policy" have changed; update the documentation to reflect that. Signed-off-by: Alexander Shishkin --- Documentation/trace/stm.rst | 36 +++++++++++++++++++++++++++--------- 1 file changed, 27 insertions(+), 9 deletions(-) diff --git a/Documentation/trace/stm.rst b/Documentation/trace/stm.rst index 2c22ddb7fd3e..944994fd6368 100644 --- a/Documentation/trace/stm.rst +++ b/Documentation/trace/stm.rst @@ -53,12 +53,30 @@ under "user" directory from the example above and this new rule will 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 +110,9 @@ allocated for the device according to the policy configuration. If 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 =========== -- 2.19.0