logging: enable setting custom logging output func

To enable custom formatting of the log output while still using existing
backend, this commit adds the `log_output_custom` feature.
To use, register a commit with `log_custom_output_msg_set` then set the
log backend format set using `log_backend_format_set` with
`LOG_OUTPUT_CUSTOM`

Signed-off-by: Lucas Denefle <lucas.denefle@converge.io>

include/zephyr/logging/log_output.h

@@ -61,6 +61,8 @@ extern "C" {
 
 #define LOG_OUTPUT_DICT 2
 
+#define LOG_OUTPUT_CUSTOM 3
+
 /**
  * @brief Prototype of the function processing output data.
  *

include/zephyr/logging/log_output_custom.h

@@ -0,0 +1,47 @@
+/*
+ * Copyright (c) 2021 Converge
+ *
+ * SPDX-License-Identifier: Apache-2.0
+ */
+#ifndef ZEPHYR_INCLUDE_LOGGING_LOG_OUTPUT_CUSTOM_H_
+#define ZEPHYR_INCLUDE_LOGGING_LOG_OUTPUT_CUSTOM_H_
+
+#include <zephyr/logging/log_output.h>
+
+#ifdef __cplusplus
+extern "C" {
+#endif
+
+/** @brief Custom logging output formatting.
+ * @ingroup log_output
+ * @{
+ */
+
+/** @brief Process log messages from an external output function set with
+ * log_custom_output_msg_set
+ *
+ * Function is using provided context with the buffer and output function to
+ * process formatted string and output the data.
+ *
+ * @param log_output Pointer to the log output instance.
+ * @param msg Log message.
+ * @param flags Optional flags.
+ */
+void log_custom_output_msg_process(const struct log_output *log_output,
+				 struct log_msg *msg, uint32_t flags);
+
+/** @brief Set the formatting log function that will be applied with LOG_OUTPUT_CUSTOM
+ *
+ * @param format Pointer to the external formatter function
+ */
+void log_custom_output_msg_set(log_format_func_t format);
+
+/**
+ * @}
+ */
+
+#ifdef __cplusplus
+}
+#endif
+
+#endif /* ZEPHYR_INCLUDE_LOGGING_LOG_OUTPUT_CUSTOM_H_ */

subsys/logging/CMakeLists.txt

@@ -54,6 +54,10 @@ if(NOT CONFIG_LOG_MODE_MINIMAL)
 
   add_subdirectory(backends)
 
+  if(CONFIG_LOG_CUSTOM_FORMAT_SUPPORT)
+    zephyr_sources(log_output_custom.c)
+  endif()
+
 else()
   zephyr_sources(log_minimal.c)
 endif()

subsys/logging/Kconfig.formatting

@@ -104,6 +104,13 @@ config LOG_DICTIONARY_SUPPORT
 
 	  This should be selected by the backend automatically.
 
+config LOG_CUSTOM_FORMAT_SUPPORT
+	bool "Custom format support"
+	default n
+	help
+	  Enable support for custom formatter.
+	  Allows custom format callbacks registering for logging backend.
+
 config LOG_IMMEDIATE_CLEAN_OUTPUT
 	bool "Clean log output"
 	depends on LOG_MODE_IMMEDIATE

subsys/logging/Kconfig.template.log_format_config

@@ -22,6 +22,11 @@ config LOG_BACKEND_$(backend)_OUTPUT_DICTIONARY
 	help
 	  Backend is in dictionary-based logging output mode.
 
+config LOG_BACKEND_$(backend)_OUTPUT_CUSTOM
+	bool "Extern"
+	help
+	  Custom formatting function can be set externally.
+
 endchoice
 
 # The numbering of the format types should be consistent across
@@ -34,3 +39,4 @@ config LOG_BACKEND_$(backend)_OUTPUT_DEFAULT
 	default 0 if LOG_BACKEND_$(backend)_OUTPUT_TEXT
 	default 1 if LOG_BACKEND_$(backend)_OUTPUT_SYST
 	default 2 if LOG_BACKEND_$(backend)_OUTPUT_DICTIONARY
+	default 3 if LOG_BACKEND_$(backend)_OUTPUT_CUSTOM

subsys/logging/log_core.c

@@ -18,6 +18,7 @@
 #include <zephyr/logging/log_frontend.h>
 #include <zephyr/syscall_handler.h>
 #include <zephyr/logging/log_output_dict.h>
+#include <zephyr/logging/log_output_custom.h>
 #include <zephyr/linker/utils.h>
 
 LOG_MODULE_REGISTER(log);
@@ -65,7 +66,9 @@ static const log_format_func_t format_table[] = {
 	[LOG_OUTPUT_SYST] = IS_ENABLED(CONFIG_LOG_MIPI_SYST_ENABLE) ?
 						log_output_msg_syst_process : NULL,
 	[LOG_OUTPUT_DICT] = IS_ENABLED(CONFIG_LOG_DICTIONARY_SUPPORT) ?
-						log_dict_output_msg_process : NULL
+						log_dict_output_msg_process : NULL,
+	[LOG_OUTPUT_CUSTOM] = IS_ENABLED(CONFIG_LOG_CUSTOM_FORMAT_SUPPORT) ?
+						log_custom_output_msg_process : NULL,
 };
 
 log_format_func_t log_format_func_t_get(uint32_t log_type)

subsys/logging/log_output_custom.c

@@ -0,0 +1,22 @@
+/*
+ * Copyright (c) 2022 Converge
+ *
+ * SPDX-License-Identifier: Apache-2.0
+ */
+#include <zephyr/logging/log.h>
+#include <zephyr/logging/log_output.h>
+
+static log_format_func_t log_custom_format_func;
+
+void log_custom_output_msg_process(const struct log_output *output, struct log_msg *msg,
+				   uint32_t flags)
+{
+	if (log_custom_format_func) {
+		log_custom_format_func(output, msg, flags);
+	}
+}
+
+void log_custom_output_msg_set(log_format_func_t format)
+{
+	log_custom_format_func = format;
+}

tests/subsys/logging/log_switch_format/overlay_custom_output.conf

@@ -0,0 +1 @@
+CONFIG_LOG_CUSTOM_FORMAT_SUPPORT=y

tests/subsys/logging/log_switch_format/src/main.c

@@ -8,9 +8,11 @@
 #include <zephyr/logging/log.h>
 #include "mock_backend.h"
 #include <zephyr/sys/printk.h>
+
 #include <zephyr/logging/log_ctrl.h>
 #include <zephyr/logging/log_output.h>
 #include <zephyr/logging/log_output_dict.h>
+#include <zephyr/logging/log_output_custom.h>
 #include <zephyr/ztest.h>
 
 #define LOG_MODULE_NAME log_switch_format
@@ -24,7 +26,7 @@ void log_msgs(void)
 	/* standard print */
 	LOG_ERR("Error message example.");
 
-#if CONFIG_LOG_MODE_DEFERRED
+#if CONFIG_LOG_MODE_DEFERRED && !(CONFIG_LOG_CUSTOM_FORMAT_SUPPORT)
 	/*
 	 * When deferred logging is enabled, the work is being performed by
 	 * another thread. The semaphore my_sem gives that thread time to process
@@ -76,7 +78,6 @@ void test_log_switch_format_success_case(void)
 
 	log_msgs();
 	validate_log_type(raw_data_str, log_type);
-
 }
 
 void test_log_switch_format_set(void)
@@ -105,7 +106,6 @@ void test_log_switch_format_set(void)
 	ret = log_backend_format_set(backend, log_type);
 
 	zassert_equal(ret, -EINVAL, "Log type not supported, Invalid value returned");
-
 }
 
 void test_log_switch_format_set_all_active_backends(void)
@@ -127,22 +127,25 @@ void test_log_switch_format_set_all_active_backends(void)
 void test_log_switch_format_func_t_get(void)
 {
 	const log_format_func_t expected_values[] = {
-	[LOG_OUTPUT_TEXT] = IS_ENABLED(CONFIG_LOG_OUTPUT) ?
+		[LOG_OUTPUT_TEXT] = IS_ENABLED(CONFIG_LOG_OUTPUT) ? log_output_msg_process : NULL,
-						log_output_msg_process : NULL,
+		[LOG_OUTPUT_SYST] = IS_ENABLED(CONFIG_LOG_MIPI_SYST_ENABLE)
-	[LOG_OUTPUT_SYST] = IS_ENABLED(CONFIG_LOG_MIPI_SYST_ENABLE) ?
+					    ? log_output_msg_syst_process
-						log_output_msg_syst_process : NULL,
+					    : NULL,
-	[LOG_OUTPUT_DICT] = IS_ENABLED(CONFIG_LOG_DICTIONARY_SUPPORT) ?
+		[LOG_OUTPUT_DICT] = IS_ENABLED(CONFIG_LOG_DICTIONARY_SUPPORT)
-						log_dict_output_msg_process : NULL
+					    ? log_dict_output_msg_process
+					    : NULL,
+		[LOG_OUTPUT_CUSTOM] = IS_ENABLED(CONFIG_LOG_CUSTOM_FORMAT_SUPPORT)
+					      ? log_custom_output_msg_process
+					      : NULL,
 	};
 
 	zassert_equal(log_format_table_size(), ARRAY_SIZE(expected_values),
-					       "Update test for expected_values table");
+		      "Update test for expected_values table");
 
 	for (int i = 0; i < ARRAY_SIZE(expected_values); i++) {
 		zassert_equal(log_format_func_t_get(i), expected_values[i],
-							"Log Format Not supported");
+			      "Log Format Not supported");
 	}
-
 }
 
 ZTEST(log_switch_format, test_log_switch_format)
@@ -153,4 +156,67 @@ ZTEST(log_switch_format, test_log_switch_format)
 	test_log_switch_format_func_t_get();
 }
 
+#if CONFIG_LOG_CUSTOM_FORMAT_SUPPORT
+void custom_formatting(const struct log_output *output, struct log_msg *msg, uint32_t flags)
+{
+	uint8_t buffer[] = "Hello world";
+
+	output->func((uint8_t *)buffer, sizeof(buffer), (void *)output);
+}
+
+ZTEST(log_switch_format, test_log_switch_format_custom_output_handles_null)
+{
+	const char *backend_name;
+	const struct log_backend *backend;
+
+	backend_name = CONFIG_LOG_BACKEND_DEFAULT;
+	backend = log_backend_get_by_name(backend_name);
+
+	log_backend_format_set(backend, LOG_OUTPUT_CUSTOM);
+
+	log_custom_output_msg_set(NULL);
+
+	log_msgs();
+
+	validate_log_type("", LOG_OUTPUT_CUSTOM);
+}
+
+ZTEST(log_switch_format, test_log_switch_format_custom_output_called_when_set)
+{
+	uint32_t log_type;
+	const char *backend_name;
+	const char *raw_data_str;
+	const char *text_custom_data_str = "Hello world";
+	const struct log_backend *backend;
+
+	backend_name = CONFIG_LOG_BACKEND_DEFAULT;
+	backend = log_backend_get_by_name(backend_name);
+
+	log_backend_format_set(backend, LOG_OUTPUT_CUSTOM);
+
+	log_custom_output_msg_set(custom_formatting);
+
+	log_msgs();
+
+	log_type = LOG_OUTPUT_CUSTOM;
+	raw_data_str = text_custom_data_str;
+	validate_log_type(raw_data_str, log_type);
+}
+
+ZTEST(log_switch_format, test_log_switch_format_does_not_log_when_uninit)
+{
+	const char *backend_name;
+	const struct log_backend *backend;
+
+	backend_name = CONFIG_LOG_BACKEND_DEFAULT;
+	backend = log_backend_get_by_name(backend_name);
+
+	log_backend_format_set(backend, LOG_OUTPUT_CUSTOM);
+
+	log_msgs();
+
+	validate_log_type("", LOG_OUTPUT_CUSTOM);
+}
+#endif
+
 ZTEST_SUITE(log_switch_format, NULL, NULL, NULL, NULL, NULL);

tests/subsys/logging/log_switch_format/testcase.yaml

@@ -19,3 +19,10 @@ tests:
       - qemu_x86
       - sam_e70_xplained
       - qemu_cortex_a53
+  logging.log_switch_format.custom_output:
+    extra_args: OVERLAY_CONFIG=overlay_custom_output.conf
+    integration_platforms:
+      - mps2_an385
+      - qemu_x86
+      - sam_e70_xplained
+      - qemu_cortex_a53