Update <system_properties.h> documentation.
Change-Id: I70de8dee963d00c480e0cb2faa9988d1d6c76d05
diff --git a/libc/include/sys/system_properties.h b/libc/include/sys/system_properties.h
index dc869da..ae94db5 100644
--- a/libc/include/sys/system_properties.h
+++ b/libc/include/sys/system_properties.h
@@ -26,8 +26,12 @@
* SUCH DAMAGE.
*/
-#ifndef _INCLUDE_SYS_SYSTEM_PROPERTIES_H
-#define _INCLUDE_SYS_SYSTEM_PROPERTIES_H
+#pragma once
+
+/**
+ * @file system_properties.h
+ * @brief System properties.
+ */
#include <sys/cdefs.h>
#include <stdbool.h>
@@ -36,39 +40,53 @@
__BEGIN_DECLS
+/** An opaque structure representing a system property. */
typedef struct prop_info prop_info;
+/**
+ * The limit on the length of a property value.
+ * (See PROP_NAME_MAX for property names.)
+ */
#define PROP_VALUE_MAX 92
-/*
+/**
* Sets system property `name` to `value`, creating the system property if it doesn't already exist.
+ *
+ * Returns 0 on success, or -1 on failure.
*/
int __system_property_set(const char* _Nonnull __name, const char* _Nonnull __value);
-/*
+/**
* Returns a `prop_info` corresponding system property `name`, or nullptr if it doesn't exist.
- * Use __system_property_read_callback to query the current value.
+ * Use __system_property_read_callback() to query the current value.
*
- * Property lookup is expensive, so it can be useful to cache the result of this function.
+ * Property lookup is expensive, so it can be useful to cache the result of this
+ * function rather than using __system_property_get().
*/
const prop_info* _Nullable __system_property_find(const char* _Nonnull __name);
-/*
- * Calls `callback` with a consistent trio of name, value, and serial number for property `pi`.
+/**
+ * Calls `callback` with a consistent trio of name, value, and serial number
+ * for property `pi`.
+ *
+ * Available since API level 26.
*/
void __system_property_read_callback(const prop_info* _Nonnull __pi,
void (* _Nonnull __callback)(void* _Nullable __cookie, const char* _Nonnull __name, const char* _Nonnull __value, uint32_t __serial),
void* _Nullable __cookie) __INTRODUCED_IN(26);
-/*
+/**
* Passes a `prop_info` for each system property to the provided
- * callback. Use __system_property_read_callback() to read the value.
+ * callback. Use __system_property_read_callback() to read the value of
+ * any of the properties.
*
* This method is for inspecting and debugging the property system, and not generally useful.
+ *
+ * Returns 0 on success, or -1 on failure.
*/
int __system_property_foreach(void (* _Nonnull __callback)(const prop_info* _Nonnull __pi, void* _Nullable __cookie), void* _Nullable __cookie);
-/*
+/**
* Waits for the specific system property identified by `pi` to be updated
* past `old_serial`. Waits no longer than `relative_timeout`, or forever
* if `relative_timeout` is null.
@@ -79,20 +97,24 @@
*
* Returns true and updates `*new_serial_ptr` on success, or false if the call
* timed out.
+ *
+ * Available since API level 26.
*/
struct timespec;
bool __system_property_wait(const prop_info* _Nullable __pi, uint32_t __old_serial, uint32_t* _Nonnull __new_serial_ptr, const struct timespec* _Nullable __relative_timeout)
__INTRODUCED_IN(26);
-/* Deprecated. In Android O and above, there's no limit on property name length. */
+/**
+ * Deprecated: there's no limit on the length of a property name since
+ * API level 26, though the limit on property values (PROP_VALUE_MAX) remains.
+ */
#define PROP_NAME_MAX 32
-/* Deprecated. Use __system_property_read_callback instead. */
+
+/** Deprecated. Use __system_property_read_callback() instead. */
int __system_property_read(const prop_info* _Nonnull __pi, char* _Nullable __name, char* _Nonnull __value);
-/* Deprecated. Use __system_property_read_callback instead. */
+/** Deprecated. Use __system_property_read_callback() instead. */
int __system_property_get(const char* _Nonnull __name, char* _Nonnull __value);
-/* Deprecated. Use __system_property_foreach instead. */
+/** Deprecated. Use __system_property_foreach() instead. */
const prop_info* _Nullable __system_property_find_nth(unsigned __n);
__END_DECLS
-
-#endif