Contents of /tags/mkinitrd-6_2_3/busybox/util-linux/hwclock.c
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Mon May 31 20:54:44 2010 UTC (14 years, 3 months ago) by niro
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Mon May 31 20:54:44 2010 UTC (14 years, 3 months ago) by niro
File MIME type: text/plain
File size: 7312 byte(s)
tagged 'mkinitrd-6_2_3'
1 | /* vi: set sw=4 ts=4: */ |
2 | /* |
3 | * Mini hwclock implementation for busybox |
4 | * |
5 | * Copyright (C) 2002 Robert Griebl <griebl@gmx.de> |
6 | * |
7 | * Licensed under GPLv2 or later, see file LICENSE in this tarball for details. |
8 | */ |
9 | |
10 | #include "libbb.h" |
11 | /* After libbb.h, since it needs sys/types.h on some systems */ |
12 | #include <sys/utsname.h> |
13 | #include "rtc_.h" |
14 | |
15 | #if ENABLE_FEATURE_HWCLOCK_LONG_OPTIONS |
16 | # ifndef _GNU_SOURCE |
17 | # define _GNU_SOURCE |
18 | # endif |
19 | #endif |
20 | |
21 | |
22 | /* diff code is disabled: it's not sys/hw clock diff, it's some useless |
23 | * "time between hwclock was started and we saw CMOS tick" quantity. |
24 | * It's useless since hwclock is started at a random moment, |
25 | * thus the quantity is also random, useless. Showing 0.000000 does not |
26 | * deprive us from any useful info. |
27 | * |
28 | * SHOW_HWCLOCK_DIFF code in this file shows the difference between system |
29 | * and hw clock. It is useful, but not compatible with standard hwclock. |
30 | * Thus disabled. |
31 | */ |
32 | #define SHOW_HWCLOCK_DIFF 0 |
33 | |
34 | |
35 | #if !SHOW_HWCLOCK_DIFF |
36 | # define read_rtc(pp_rtcname, sys_tv, utc) read_rtc(pp_rtcname, utc) |
37 | #endif |
38 | static time_t read_rtc(const char **pp_rtcname, struct timeval *sys_tv, int utc) |
39 | { |
40 | struct tm tm_time; |
41 | int fd; |
42 | |
43 | fd = rtc_xopen(pp_rtcname, O_RDONLY); |
44 | |
45 | rtc_read_tm(&tm_time, fd); |
46 | |
47 | #if SHOW_HWCLOCK_DIFF |
48 | { |
49 | int before = tm_time.tm_sec; |
50 | while (1) { |
51 | rtc_read_tm(&tm_time, fd); |
52 | gettimeofday(sys_tv, NULL); |
53 | if (before != tm_time.tm_sec) |
54 | break; |
55 | } |
56 | } |
57 | #endif |
58 | |
59 | if (ENABLE_FEATURE_CLEAN_UP) |
60 | close(fd); |
61 | |
62 | return rtc_tm2time(&tm_time, utc); |
63 | } |
64 | |
65 | static void show_clock(const char **pp_rtcname, int utc) |
66 | { |
67 | #if SHOW_HWCLOCK_DIFF |
68 | struct timeval sys_tv; |
69 | #endif |
70 | time_t t; |
71 | char *cp; |
72 | |
73 | t = read_rtc(pp_rtcname, &sys_tv, utc); |
74 | cp = ctime(&t); |
75 | strchrnul(cp, '\n')[0] = '\0'; |
76 | #if !SHOW_HWCLOCK_DIFF |
77 | printf("%s 0.000000 seconds\n", cp); |
78 | #else |
79 | { |
80 | long diff = sys_tv.tv_sec - t; |
81 | if (diff < 0 /*&& tv.tv_usec != 0*/) { |
82 | /* Why? */ |
83 | /* diff >= 0 is ok: diff < 0, can't just use tv.tv_usec: */ |
84 | /* 45.520820 43.520820 */ |
85 | /* - 44.000000 - 45.000000 */ |
86 | /* = 1.520820 = -1.479180, not -2.520820! */ |
87 | diff++; |
88 | /* should be 1000000 - tv.tv_usec, but then we must check tv.tv_usec != 0 */ |
89 | sys_tv.tv_usec = 999999 - sys_tv.tv_usec; |
90 | } |
91 | printf("%s %ld.%06lu seconds\n", cp, diff, (unsigned long)sys_tv.tv_usec); |
92 | } |
93 | #endif |
94 | } |
95 | |
96 | static void to_sys_clock(const char **pp_rtcname, int utc) |
97 | { |
98 | struct timeval tv; |
99 | struct timezone tz; |
100 | |
101 | tz.tz_minuteswest = timezone/60 - 60*daylight; |
102 | tz.tz_dsttime = 0; |
103 | |
104 | tv.tv_sec = read_rtc(pp_rtcname, NULL, utc); |
105 | tv.tv_usec = 0; |
106 | if (settimeofday(&tv, &tz)) |
107 | bb_perror_msg_and_die("settimeofday"); |
108 | } |
109 | |
110 | static void from_sys_clock(const char **pp_rtcname, int utc) |
111 | { |
112 | #if 1 |
113 | struct timeval tv; |
114 | struct tm tm_time; |
115 | int rtc; |
116 | |
117 | rtc = rtc_xopen(pp_rtcname, O_WRONLY); |
118 | gettimeofday(&tv, NULL); |
119 | /* Prepare tm_time */ |
120 | if (sizeof(time_t) == sizeof(tv.tv_sec)) { |
121 | if (utc) |
122 | gmtime_r((time_t*)&tv.tv_sec, &tm_time); |
123 | else |
124 | localtime_r((time_t*)&tv.tv_sec, &tm_time); |
125 | } else { |
126 | time_t t = tv.tv_sec; |
127 | if (utc) |
128 | gmtime_r(&t, &tm_time); |
129 | else |
130 | localtime_r(&t, &tm_time); |
131 | } |
132 | #else |
133 | /* Bloated code which tries to set hw clock with better precision. |
134 | * On x86, even though code does set hw clock within <1ms of exact |
135 | * whole seconds, apparently hw clock (at least on some machines) |
136 | * doesn't reset internal fractional seconds to 0, |
137 | * making all this a pointless excercise. |
138 | */ |
139 | /* If we see that we are N usec away from whole second, |
140 | * we'll sleep for N-ADJ usecs. ADJ corrects for the fact |
141 | * that CPU is not infinitely fast. |
142 | * On infinitely fast CPU, next wakeup would be |
143 | * on (exactly_next_whole_second - ADJ). On real CPUs, |
144 | * this difference between current time and whole second |
145 | * is less than ADJ (assuming system isn't heavily loaded). |
146 | */ |
147 | /* Small value of 256us gives very precise sync for 2+ GHz CPUs. |
148 | * Slower CPUs will fail to sync and will go to bigger |
149 | * ADJ values. qemu-emulated armv4tl with ~100 MHz |
150 | * performance ends up using ADJ ~= 4*1024 and it takes |
151 | * 2+ secs (2 tries with successively larger ADJ) |
152 | * to sync. Even straced one on the same qemu (very slow) |
153 | * takes only 4 tries. |
154 | */ |
155 | #define TWEAK_USEC 256 |
156 | unsigned adj = TWEAK_USEC; |
157 | struct tm tm_time; |
158 | struct timeval tv; |
159 | int rtc = rtc_xopen(pp_rtcname, O_WRONLY); |
160 | |
161 | /* Try to catch the moment when whole second is close */ |
162 | while (1) { |
163 | unsigned rem_usec; |
164 | time_t t; |
165 | |
166 | gettimeofday(&tv, NULL); |
167 | |
168 | t = tv.tv_sec; |
169 | rem_usec = 1000000 - tv.tv_usec; |
170 | if (rem_usec < adj) { |
171 | /* Close enough */ |
172 | small_rem: |
173 | t++; |
174 | } |
175 | |
176 | /* Prepare tm_time from t */ |
177 | if (utc) |
178 | gmtime_r(&t, &tm_time); /* may read /etc/xxx (it takes time) */ |
179 | else |
180 | localtime_r(&t, &tm_time); /* same */ |
181 | |
182 | if (adj >= 32*1024) { |
183 | break; /* 32 ms diff and still no luck?? give up trying to sync */ |
184 | } |
185 | |
186 | /* gmtime/localtime took some time, re-get cur time */ |
187 | gettimeofday(&tv, NULL); |
188 | |
189 | if (tv.tv_sec < t /* we are still in old second */ |
190 | || (tv.tv_sec == t && tv.tv_usec < adj) /* not too far into next second */ |
191 | ) { |
192 | break; /* good, we are in sync! */ |
193 | } |
194 | |
195 | rem_usec = 1000000 - tv.tv_usec; |
196 | if (rem_usec < adj) { |
197 | t = tv.tv_sec; |
198 | goto small_rem; /* already close to next sec, don't sleep */ |
199 | } |
200 | |
201 | /* Try to sync up by sleeping */ |
202 | usleep(rem_usec - adj); |
203 | |
204 | /* Jump to 1ms diff, then increase fast (x2): EVERY loop |
205 | * takes ~1 sec, people won't like slowly converging code here! |
206 | */ |
207 | //bb_error_msg("adj:%d tv.tv_usec:%d", adj, (int)tv.tv_usec); |
208 | if (adj < 512) |
209 | adj = 512; |
210 | /* ... and if last "overshoot" does not look insanely big, |
211 | * just use it as adj increment. This makes convergence faster. |
212 | */ |
213 | if (tv.tv_usec < adj * 8) { |
214 | adj += tv.tv_usec; |
215 | continue; |
216 | } |
217 | adj *= 2; |
218 | } |
219 | /* Debug aid to find "optimal" TWEAK_USEC with nearly exact sync. |
220 | * Look for a value which makes tv_usec close to 999999 or 0. |
221 | * For 2.20GHz Intel Core 2: optimal TWEAK_USEC ~= 200 |
222 | */ |
223 | //bb_error_msg("tv.tv_usec:%d", (int)tv.tv_usec); |
224 | #endif |
225 | |
226 | tm_time.tm_isdst = 0; |
227 | xioctl(rtc, RTC_SET_TIME, &tm_time); |
228 | |
229 | if (ENABLE_FEATURE_CLEAN_UP) |
230 | close(rtc); |
231 | } |
232 | |
233 | #define HWCLOCK_OPT_LOCALTIME 0x01 |
234 | #define HWCLOCK_OPT_UTC 0x02 |
235 | #define HWCLOCK_OPT_SHOW 0x04 |
236 | #define HWCLOCK_OPT_HCTOSYS 0x08 |
237 | #define HWCLOCK_OPT_SYSTOHC 0x10 |
238 | #define HWCLOCK_OPT_RTCFILE 0x20 |
239 | |
240 | int hwclock_main(int argc, char **argv) MAIN_EXTERNALLY_VISIBLE; |
241 | int hwclock_main(int argc UNUSED_PARAM, char **argv) |
242 | { |
243 | const char *rtcname = NULL; |
244 | unsigned opt; |
245 | int utc; |
246 | |
247 | #if ENABLE_FEATURE_HWCLOCK_LONG_OPTIONS |
248 | static const char hwclock_longopts[] ALIGN1 = |
249 | "localtime\0" No_argument "l" |
250 | "utc\0" No_argument "u" |
251 | "show\0" No_argument "r" |
252 | "hctosys\0" No_argument "s" |
253 | "systohc\0" No_argument "w" |
254 | "file\0" Required_argument "f" |
255 | ; |
256 | applet_long_options = hwclock_longopts; |
257 | #endif |
258 | opt_complementary = "r--ws:w--rs:s--wr:l--u:u--l"; |
259 | opt = getopt32(argv, "lurswf:", &rtcname); |
260 | |
261 | /* If -u or -l wasn't given check if we are using utc */ |
262 | if (opt & (HWCLOCK_OPT_UTC | HWCLOCK_OPT_LOCALTIME)) |
263 | utc = (opt & HWCLOCK_OPT_UTC); |
264 | else |
265 | utc = rtc_adjtime_is_utc(); |
266 | |
267 | if (opt & HWCLOCK_OPT_HCTOSYS) |
268 | to_sys_clock(&rtcname, utc); |
269 | else if (opt & HWCLOCK_OPT_SYSTOHC) |
270 | from_sys_clock(&rtcname, utc); |
271 | else |
272 | /* default HWCLOCK_OPT_SHOW */ |
273 | show_clock(&rtcname, utc); |
274 | |
275 | return 0; |
276 | } |