1 /* 2 * Copyright (C) 2008 The Android Open Source Project 3 * All rights reserved. 4 * 5 * Redistribution and use in source and binary forms, with or without 6 * modification, are permitted provided that the following conditions 7 * are met: 8 * * Redistributions of source code must retain the above copyright 9 * notice, this list of conditions and the following disclaimer. 10 * * Redistributions in binary form must reproduce the above copyright 11 * notice, this list of conditions and the following disclaimer in 12 * the documentation and/or other materials provided with the 13 * distribution. 14 * 15 * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS 16 * "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT 17 * LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS 18 * FOR A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE 19 * COPYRIGHT OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, 20 * INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, 21 * BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS 22 * OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED 23 * AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, 24 * OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT 25 * OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF 26 * SUCH DAMAGE. 27 */ 28 29 #ifndef _INCLUDE_SYS__SYSTEM_PROPERTIES_H 30 #define _INCLUDE_SYS__SYSTEM_PROPERTIES_H 31 32 #ifndef _REALLY_INCLUDE_SYS__SYSTEM_PROPERTIES_H_ 33 #error you should #include <sys/system_properties.h> instead 34 #else 35 #include <sys/system_properties.h> 36 37 typedef struct prop_msg prop_msg; 38 39 #define PROP_AREA_MAGIC 0x504f5250 40 #define PROP_AREA_VERSION 0xfc6ed0ab 41 #define PROP_AREA_VERSION_COMPAT 0x45434f76 42 43 #define PROP_SERVICE_NAME "property_service" 44 #define PROP_FILENAME "/dev/__properties__" 45 46 #define PA_SIZE (128 * 1024) 47 48 #define SERIAL_VALUE_LEN(serial) ((serial) >> 24) 49 #define SERIAL_DIRTY(serial) ((serial) & 1) 50 51 __BEGIN_DECLS 52 53 struct prop_msg 54 { 55 unsigned cmd; 56 char name[PROP_NAME_MAX]; 57 char value[PROP_VALUE_MAX]; 58 }; 59 60 #define PROP_MSG_SETPROP 1 61 62 /* 63 ** Rules: 64 ** 65 ** - there is only one writer, but many readers 66 ** - prop_area.count will never decrease in value 67 ** - once allocated, a prop_info's name will not change 68 ** - once allocated, a prop_info's offset will not change 69 ** - reading a value requires the following steps 70 ** 1. serial = pi->serial 71 ** 2. if SERIAL_DIRTY(serial), wait*, then goto 1 72 ** 3. memcpy(local, pi->value, SERIAL_VALUE_LEN(serial) + 1) 73 ** 4. if pi->serial != serial, goto 2 74 ** 75 ** - writing a value requires the following steps 76 ** 1. pi->serial = pi->serial | 1 77 ** 2. memcpy(pi->value, local_value, value_len) 78 ** 3. pi->serial = (value_len << 24) | ((pi->serial + 1) & 0xffffff) 79 */ 80 81 #define PROP_PATH_RAMDISK_DEFAULT "/default.prop" 82 #define PROP_PATH_SYSTEM_BUILD "/system/build.prop" 83 #define PROP_PATH_VENDOR_BUILD "/vendor/build.prop" 84 #define PROP_PATH_LOCAL_OVERRIDE "/data/local.prop" 85 #define PROP_PATH_FACTORY "/factory/factory.prop" 86 87 /* 88 ** Map the property area from the specified filename. This 89 ** method is for testing only. 90 */ 91 int __system_property_set_filename(const char *filename); 92 93 /* 94 ** Initialize the area to be used to store properties. Can 95 ** only be done by a single process that has write access to 96 ** the property area. 97 */ 98 int __system_property_area_init(); 99 100 /* Read the global serial number of the system properties 101 ** 102 ** Called to predict if a series of cached __system_property_find 103 ** objects will have seen __system_property_serial values change. 104 ** But also aids the converse, as changes in the global serial can 105 ** also be used to predict if a failed __system_property_find 106 ** could in-turn now find a new object; thus preventing the 107 ** cycles of effort to poll __system_property_find. 108 ** 109 ** Typically called at beginning of a cache cycle to signal if _any_ possible 110 ** changes have occurred since last. If there is, one may check each individual 111 ** __system_property_serial to confirm dirty, or __system_property_find 112 ** to check if the property now exists. If a call to __system_property_add 113 ** or __system_property_update has completed between two calls to 114 ** __system_property_area_serial then the second call will return a larger 115 ** value than the first call. Beware of race conditions as changes to the 116 ** properties are not atomic, the main value of this call is to determine 117 ** whether the expensive __system_property_find is worth retrying to see if 118 ** a property now exists. 119 ** 120 ** Returns the serial number on success, -1 on error. 121 */ 122 unsigned int __system_property_area_serial(); 123 124 /* Add a new system property. Can only be done by a single 125 ** process that has write access to the property area, and 126 ** that process must handle sequencing to ensure the property 127 ** does not already exist and that only one property is added 128 ** or updated at a time. 129 ** 130 ** Returns 0 on success, -1 if the property area is full. 131 */ 132 int __system_property_add(const char *name, unsigned int namelen, 133 const char *value, unsigned int valuelen); 134 135 /* Update the value of a system property returned by 136 ** __system_property_find. Can only be done by a single process 137 ** that has write access to the property area, and that process 138 ** must handle sequencing to ensure that only one property is 139 ** updated at a time. 140 ** 141 ** Returns 0 on success, -1 if the parameters are incorrect. 142 */ 143 int __system_property_update(prop_info *pi, const char *value, unsigned int len); 144 145 /* Read the serial number of a system property returned by 146 ** __system_property_find. 147 ** 148 ** Returns the serial number on success, -1 on error. 149 */ 150 unsigned int __system_property_serial(const prop_info *pi); 151 152 /* Wait for any system property to be updated. Caller must pass 153 ** in 0 the first time, and the previous return value on each 154 ** successive call. */ 155 unsigned int __system_property_wait_any(unsigned int serial); 156 157 /* Compatibility functions to support using an old init with a new libc, 158 ** mostly for the OTA updater binary. These can be deleted once OTAs from 159 ** a pre-K release no longer needed to be supported. */ 160 const prop_info *__system_property_find_compat(const char *name); 161 int __system_property_read_compat(const prop_info *pi, char *name, char *value); 162 int __system_property_foreach_compat( 163 void (*propfn)(const prop_info *pi, void *cookie), 164 void *cookie); 165 166 /* Initialize the system properties area in read only mode. 167 * Should be done by all processes that need to read system 168 * properties. 169 * 170 * Returns 0 on success, -1 otherwise. 171 */ 172 int __system_properties_init(); 173 174 __END_DECLS 175 176 #endif 177 #endif 178