From patchwork Thu Jan 7 08:32:47 2021 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: "Tzvetomir Stoyanov (VMware)" X-Patchwork-Id: 12003161 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=-15.8 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 9BAE2C433E6 for ; Thu, 7 Jan 2021 08:33:38 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id 5683F20738 for ; Thu, 7 Jan 2021 08:33:38 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1726338AbhAGIdi (ORCPT ); Thu, 7 Jan 2021 03:33:38 -0500 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:56990 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1725900AbhAGIdh (ORCPT ); Thu, 7 Jan 2021 03:33:37 -0500 Received: from mail-wr1-x42c.google.com (mail-wr1-x42c.google.com [IPv6:2a00:1450:4864:20::42c]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id 59A6BC0612F9 for ; Thu, 7 Jan 2021 00:32:57 -0800 (PST) Received: by mail-wr1-x42c.google.com with SMTP id y17so4735439wrr.10 for ; Thu, 07 Jan 2021 00:32:57 -0800 (PST) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=gmail.com; s=20161025; h=from:to:cc:subject:date:message-id:in-reply-to:references :mime-version:content-transfer-encoding; bh=haKTlhRBvQnAoCt7ye6uAWGXu2XyjhNIGokztycdGfI=; b=DUPLG9dVeHK/15o/vAmHV6fmDYF7oYh6cxxGpTbh3BNLLzUFIqAjEv8TER+vaZUeaO k2x4jRQ60LKShJK2RsMjHQJ+EMMDMPMRxCDORMGakkWNd+XZ9Uyz14Ee0rqTqeE4WvYK /7awd09IRqIi7ugzZBJNcdj1qtlg/TbcdbftcIiXRcTjDBx2xX3bjqZL0nM4P6dKBoJB O0sy8X14HU9eJPReR3drxCRBaFQ0kPanuiJRS2jTMCYkp2AojULpRcuwiBWhiHbVLt+z SAPX/UsWtZsux3UafR+nIxLYzzTe63rKmfSkzzYf5cy+8J6TLxe5A2b0UhSQELqRSuH7 88nw== X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20161025; h=x-gm-message-state:from:to:cc:subject:date:message-id:in-reply-to :references:mime-version:content-transfer-encoding; bh=haKTlhRBvQnAoCt7ye6uAWGXu2XyjhNIGokztycdGfI=; b=ebNY5UMw2UKTfme8lHk21UK4vH5fGOe7Ya2k6AHaj2zfs2uVfjWCsjn5bW6TgPUVxr AW1FZhCQFWvwX/QyuyTfQ+Egz8nW8v+YAjbeCVz3MG98dzNst6R6D500x3XhINkhL3r3 KCd1e8aea61HPD5ZDH1TDkJQ/BoENfvJu8BxQs2bP6Zb/If/sfB3q9jw7v2VJdEsKvhF W3W4hJwJa2mnNzTXbMm9Brai7gC1XI/t0kLKploaJ9C66bOIOAzpO6DpnosIj+ozQ8ss FYzW3Hf9/oK99PFypa9Inn+ZfOvVdlhI+mgb7gMbdxZgpmXeSqnAMDdNjZ54Hn/mcgVw 3B1A== X-Gm-Message-State: AOAM531z3qbAfxRkHGYy9sk346+DS4mtqHvqv2ow4h3zcK/OFae2Ky2+ do5hmNtOWM2oOuk4yKk988p11tbvg8ppHbi6 X-Google-Smtp-Source: ABdhPJzltPSPyJPu2RrFhJvEJOh7PdQhu6+/fPbkFhMVJwUYuu83OhWVp2SriSuHMORrRO6lUf0ETQ== X-Received: by 2002:adf:eec6:: with SMTP id a6mr7750334wrp.239.1610008376150; Thu, 07 Jan 2021 00:32:56 -0800 (PST) Received: from oberon.zico.biz ([83.222.187.186]) by smtp.gmail.com with ESMTPSA id v20sm7293867wra.19.2021.01.07.00.32.55 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Thu, 07 Jan 2021 00:32:55 -0800 (PST) From: "Tzvetomir Stoyanov (VMware)" To: rostedt@goodmis.org Cc: linux-trace-devel@vger.kernel.org Subject: [PATCH 3/6] libtracefs: Documentation for the new APIs for opening and reading ftrace files Date: Thu, 7 Jan 2021 10:32:47 +0200 Message-Id: <20210107083250.16295-4-tz.stoyanov@gmail.com> X-Mailer: git-send-email 2.29.2 In-Reply-To: <20210107083250.16295-1-tz.stoyanov@gmail.com> References: <20210107083250.16295-1-tz.stoyanov@gmail.com> MIME-Version: 1.0 Precedence: bulk List-ID: X-Mailing-List: linux-trace-devel@vger.kernel.org Man pages updated with documentation about: tracefs_instance_file_open(); tracefs_instance_file_read_int(); Signed-off-by: Tzvetomir Stoyanov (VMware) --- Documentation/libtracefs-instances-files.txt | 47 ++++++++++++++++++-- 1 file changed, 43 insertions(+), 4 deletions(-) diff --git a/Documentation/libtracefs-instances-files.txt b/Documentation/libtracefs-instances-files.txt index 9b18b73..d3aaef2 100644 --- a/Documentation/libtracefs-instances-files.txt +++ b/Documentation/libtracefs-instances-files.txt @@ -4,8 +4,8 @@ libtracefs(3) NAME ---- tracefs_file_exists, tracefs_dir_exists, tracefs_instance_get_file, -tracefs_instance_get_dir, tracefs_instance_file_write, -tracefs_instance_file_read - Work with files in tracing instances. +tracefs_instance_get_dir, tracefs_instance_file_open, tracefs_instance_file_write, +tracefs_instance_file_read, tracefs_instance_file_read_int - Work with files in tracing instances. SYNOPSIS -------- @@ -17,8 +17,10 @@ bool *tracefs_file_exists*(struct tracefs_instance pass:[*]_instance_, char pass bool *tracefs_dir_exists*(struct tracefs_instance pass:[*]_instance_, char pass:[*]_name_); char pass:[*]*tracefs_instance_get_file*(struct tracefs_instance pass:[*]_instance_, const char pass:[*]_file_); char pass:[*]*tracefs_instance_get_dir*(struct tracefs_instance pass:[*]_instance_); +int *tracefs_instance_file_open*(struct tracefs_instance pass:[*]_instance_, const char pass:[*]_file_, int _mode_); int *tracefs_instance_file_write*(struct tracefs_instance pass:[*]_instance_, const char pass:[*]_file_, const char pass:[*]_str_); -char pass:[*]*tracefs_instance_file_read*(struct tracefs_instance pass:[*]_instance_, char pass:[*]_file_, int pass:[*]_psize_); +char pass:[*]*tracefs_instance_file_read*(struct tracefs_instance pass:[*]_instance_, const char pass:[*]_file_, int pass:[*]_psize_); +int *tracefs_instance_file_read_int*(struct tracefs_instance pass:[*]_instance_, const char pass:[*]_file_, long long int pass:[*]_res_); -- @@ -41,12 +43,19 @@ The _tracefs_instance_get_dir()_ function returns the full path of the director with given _name_ in _instance_. Note, it does not check if the directory exists in the instance. +The _tracefs_instance_file_open()_ function opens trace _file_ from given _instance_ and returns +a file descriptor to it. The file access _mode_ can be specified, see *open*(3) for more details. +If -1 is passed as _mode_, default O_RDWR is used. + The _tracefs_instance_file_write()_ function writes a string _str_ in a _file_ from the given _instance_, without the terminating NULL character. -The _tracefs_instance_file_read()_ function reads the content of a _file_ from +The _tracefs_instance_file_read()_ function reads the content of a _file_ from the given _instance_. +The _tracefs_instance_file_read_int()_ function reads the content of a _file_ from +the given _instance_ and converts it to a long long integer, which is stored in _res_. + RETURN VALUE ------------ The _tracefs_file_exists()_ and _tracefs_dir_exists()_ functions return true if the @@ -56,6 +65,9 @@ The _tracefs_instance_get_file()_ and _tracefs_instance_get_dir()_ functions ret a string or NULL in case of an error. The returned string must be freed with _tracefs_put_tracing_file()_. +The _tracefs_instance_file_open()_ function returns a file descriptor to the opened file. It must be +closed with *close*(3). In case of an error, -1 is returned. + The _tracefs_instance_file_write()_ function returns the number of written bytes, or -1 in case of an error. @@ -63,6 +75,9 @@ The _tracefs_instance_file_read()_ function returns a pointer to a NULL terminat string, read from the file, or NULL in case of an error. The returned string must be freed with free(). +The _tracefs_instance_file_read_int()_ function returns 0 if a valid integer is read from the file +and stored in _res_ or -1 in case of an error. + EXAMPLE ------- [source,c] @@ -123,6 +138,30 @@ struct tracefs_instance *inst = tracefs_instance_create("foo"); tracefs_instance_destroy(inst); else tracefs_instance_free(inst); + ... + + long long int res; + if (tracefs_instance_file_read_int(NULL, "tracing_on", &res) == 0) { + if (res == 0) { + /* tracing is disabled in the top instance */ + } else if (res == 1) { + /* tracing is enabled in the top instance */ + } else { + /* Unknown tracing state of the top instance */ + } + } else { + /* Failed to read integer from tracing_on file */ + } + + ... + + int fd; + fd = tracefs_instance_file_open(NULL, "tracing_on", O_WRONLY); + if (fd >= 0) { + /* Got file descriptor to the tracing_on file from the top instance for writing */ + ... + close(fd); + } -- FILES -----