[dpdk-dev] [PATCH v4] log: support custom log function

[Li Feng]

By default, the dpdk log is out to stdout/stderr and syslog.
The rte_openlog_stream could set an external FILE* stream, but it
asks the consumer to give it a FILE* pointer.
For C++ or other languages, it's hard to get a libc FILE*.

Support to set a hook is another choice for this scenario.

Signed-off-by: Li Feng <fengli at smartx.com>
---
v4: Fix the code style.
v3: Rename the func, change the comments, add funcs in version.map.
v2: Simplify the code.

 lib/librte_eal/include/rte_log.h | 31 +++++++++++++++++++++++++++++++
 lib/librte_eal/linux/eal_log.c   | 23 +++++++++++++++++++++++
 lib/librte_eal/version.map       |  2 ++
 lib/librte_eal/windows/eal_log.c | 19 +++++++++++++++++++
 4 files changed, 75 insertions(+)

diff --git a/lib/librte_eal/include/rte_log.h b/lib/librte_eal/include/rte_log.h
index 173004fd7..adf299610 100644
--- a/lib/librte_eal/include/rte_log.h
+++ b/lib/librte_eal/include/rte_log.h
@@ -97,6 +97,37 @@ int rte_openlog_stream(FILE *f);
  */
 FILE *rte_log_get_stream(void);
 
+/**
+ * Define a logging write function.
+ */
+typedef ssize_t rte_log_write_function(void *cookie, const char *buf,
+	size_t size);
+
+/**
+ * Change the default stream's write action that will be used by the logging
+ * system.
+ *
+ * This should be done before the 'rte_eal_init' call. And the
+ * 'rte_openlog_stream' call will override this action.
+ *
+ * @param logf
+ *   Pointer to the log write function.
+ */
+__rte_experimental
+void
+rte_log_sink_set(rte_log_write_function *logf);
+
+/**
+ * Retrieve the log function used by the logging system (see rte_log_sink_set()
+ * to change it).
+ *
+ * @return
+ *   Pointer to the log function.
+ */
+__rte_experimental
+rte_log_write_function*
+rte_log_sink_get(void);
+
 /**
  * Set the global log level.
  *
diff --git a/lib/librte_eal/linux/eal_log.c b/lib/librte_eal/linux/eal_log.c
index 43c8460bf..fb3ac3f14 100644
--- a/lib/librte_eal/linux/eal_log.c
+++ b/lib/librte_eal/linux/eal_log.c
@@ -60,3 +60,26 @@ rte_eal_log_init(const char *id, int facility)
 
 	return 0;
 }
+
+/**
+ * Change the default stream's write action that will be used by the logging
+ * system.
+ *
+ * This should be done before the 'rte_eal_init' call. And the
+ * 'rte_openlog_stream' call will override this action.
+ */
+void
+rte_log_sink_set(rte_log_write_function *logf)
+{
+	console_log_func.write = logf;
+}
+
+/**
+ * Retrieve the log function used by the logging system (see rte_log_sink_set()
+ * to change it).
+ */
+rte_log_write_function*
+rte_log_sink_get(void)
+{
+	return console_log_func.write;
+}
diff --git a/lib/librte_eal/version.map b/lib/librte_eal/version.map
index fce90a112..04d651912 100644
--- a/lib/librte_eal/version.map
+++ b/lib/librte_eal/version.map
@@ -412,6 +412,8 @@ EXPERIMENTAL {
 	rte_thread_tls_key_delete;
 	rte_thread_tls_value_get;
 	rte_thread_tls_value_set;
+	rte_log_sink_set;
+	rte_log_sink_get;
 };
 
 INTERNAL {
diff --git a/lib/librte_eal/windows/eal_log.c b/lib/librte_eal/windows/eal_log.c
index 875981f13..589b47f27 100644
--- a/lib/librte_eal/windows/eal_log.c
+++ b/lib/librte_eal/windows/eal_log.c
@@ -14,3 +14,22 @@ rte_eal_log_init(__rte_unused const char *id, __rte_unused int facility)
 
 	return 0;
 }
+
+/*
+ * Set the customized logger, it will override the default stream write action,
+ * which is writing to syslog and stdout.
+ */
+void
+rte_log_sink_set(rte_log_write_function *logf)
+{
+	RTE_SET_USED(logf);
+}
+
+/*
+ * Retrieve the default log write function.
+ */
+rte_log_write_function*
+rte_log_sink_get(void)
+{
+	return NULL;
+}
-- 
2.29.2