Annotation of /trunk/mkinitrd-magellan/busybox/util-linux/hwclock.c
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Wed Aug 18 21:56:57 2010 UTC (13 years, 9 months ago) by niro
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Wed Aug 18 21:56:57 2010 UTC (13 years, 9 months ago) by niro
File MIME type: text/plain
File size: 7212 byte(s)
-updated to busybox-1.17.1
1 | niro | 532 | /* 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 | niro | 984 | #include "libbb.h" |
11 | /* After libbb.h, since it needs sys/types.h on some systems */ | ||
12 | niro | 532 | #include <sys/utsname.h> |
13 | niro | 816 | #include "rtc_.h" |
14 | niro | 532 | |
15 | niro | 984 | /* diff code is disabled: it's not sys/hw clock diff, it's some useless |
16 | * "time between hwclock was started and we saw CMOS tick" quantity. | ||
17 | * It's useless since hwclock is started at a random moment, | ||
18 | * thus the quantity is also random, useless. Showing 0.000000 does not | ||
19 | * deprive us from any useful info. | ||
20 | * | ||
21 | * SHOW_HWCLOCK_DIFF code in this file shows the difference between system | ||
22 | * and hw clock. It is useful, but not compatible with standard hwclock. | ||
23 | * Thus disabled. | ||
24 | */ | ||
25 | #define SHOW_HWCLOCK_DIFF 0 | ||
26 | |||
27 | |||
28 | #if !SHOW_HWCLOCK_DIFF | ||
29 | # define read_rtc(pp_rtcname, sys_tv, utc) read_rtc(pp_rtcname, utc) | ||
30 | #endif | ||
31 | static time_t read_rtc(const char **pp_rtcname, struct timeval *sys_tv, int utc) | ||
32 | niro | 532 | { |
33 | niro | 984 | struct tm tm_time; |
34 | niro | 816 | int fd; |
35 | niro | 532 | |
36 | niro | 984 | fd = rtc_xopen(pp_rtcname, O_RDONLY); |
37 | niro | 532 | |
38 | niro | 984 | rtc_read_tm(&tm_time, fd); |
39 | niro | 532 | |
40 | niro | 984 | #if SHOW_HWCLOCK_DIFF |
41 | { | ||
42 | int before = tm_time.tm_sec; | ||
43 | while (1) { | ||
44 | rtc_read_tm(&tm_time, fd); | ||
45 | gettimeofday(sys_tv, NULL); | ||
46 | if (before != tm_time.tm_sec) | ||
47 | break; | ||
48 | } | ||
49 | } | ||
50 | #endif | ||
51 | niro | 532 | |
52 | niro | 984 | if (ENABLE_FEATURE_CLEAN_UP) |
53 | close(fd); | ||
54 | niro | 532 | |
55 | niro | 984 | return rtc_tm2time(&tm_time, utc); |
56 | niro | 532 | } |
57 | |||
58 | niro | 984 | static void show_clock(const char **pp_rtcname, int utc) |
59 | niro | 532 | { |
60 | niro | 984 | #if SHOW_HWCLOCK_DIFF |
61 | struct timeval sys_tv; | ||
62 | #endif | ||
63 | niro | 532 | time_t t; |
64 | niro | 816 | char *cp; |
65 | niro | 532 | |
66 | niro | 984 | t = read_rtc(pp_rtcname, &sys_tv, utc); |
67 | niro | 816 | cp = ctime(&t); |
68 | niro | 984 | strchrnul(cp, '\n')[0] = '\0'; |
69 | #if !SHOW_HWCLOCK_DIFF | ||
70 | niro | 816 | printf("%s 0.000000 seconds\n", cp); |
71 | niro | 984 | #else |
72 | { | ||
73 | long diff = sys_tv.tv_sec - t; | ||
74 | if (diff < 0 /*&& tv.tv_usec != 0*/) { | ||
75 | /* Why? */ | ||
76 | /* diff >= 0 is ok: diff < 0, can't just use tv.tv_usec: */ | ||
77 | /* 45.520820 43.520820 */ | ||
78 | /* - 44.000000 - 45.000000 */ | ||
79 | /* = 1.520820 = -1.479180, not -2.520820! */ | ||
80 | diff++; | ||
81 | /* should be 1000000 - tv.tv_usec, but then we must check tv.tv_usec != 0 */ | ||
82 | sys_tv.tv_usec = 999999 - sys_tv.tv_usec; | ||
83 | } | ||
84 | printf("%s %ld.%06lu seconds\n", cp, diff, (unsigned long)sys_tv.tv_usec); | ||
85 | } | ||
86 | #endif | ||
87 | niro | 532 | } |
88 | |||
89 | niro | 984 | static void to_sys_clock(const char **pp_rtcname, int utc) |
90 | niro | 532 | { |
91 | niro | 816 | struct timeval tv; |
92 | niro | 984 | struct timezone tz; |
93 | niro | 532 | |
94 | niro | 984 | tz.tz_minuteswest = timezone/60 - 60*daylight; |
95 | tz.tz_dsttime = 0; | ||
96 | |||
97 | tv.tv_sec = read_rtc(pp_rtcname, NULL, utc); | ||
98 | niro | 816 | tv.tv_usec = 0; |
99 | niro | 532 | if (settimeofday(&tv, &tz)) |
100 | niro | 984 | bb_perror_msg_and_die("settimeofday"); |
101 | niro | 532 | } |
102 | |||
103 | niro | 984 | static void from_sys_clock(const char **pp_rtcname, int utc) |
104 | niro | 532 | { |
105 | niro | 990 | #if 1 |
106 | struct timeval tv; | ||
107 | niro | 984 | struct tm tm_time; |
108 | niro | 990 | int rtc; |
109 | |||
110 | rtc = rtc_xopen(pp_rtcname, O_WRONLY); | ||
111 | gettimeofday(&tv, NULL); | ||
112 | /* Prepare tm_time */ | ||
113 | if (sizeof(time_t) == sizeof(tv.tv_sec)) { | ||
114 | if (utc) | ||
115 | gmtime_r((time_t*)&tv.tv_sec, &tm_time); | ||
116 | else | ||
117 | localtime_r((time_t*)&tv.tv_sec, &tm_time); | ||
118 | } else { | ||
119 | time_t t = tv.tv_sec; | ||
120 | if (utc) | ||
121 | gmtime_r(&t, &tm_time); | ||
122 | else | ||
123 | localtime_r(&t, &tm_time); | ||
124 | } | ||
125 | #else | ||
126 | /* Bloated code which tries to set hw clock with better precision. | ||
127 | * On x86, even though code does set hw clock within <1ms of exact | ||
128 | * whole seconds, apparently hw clock (at least on some machines) | ||
129 | * doesn't reset internal fractional seconds to 0, | ||
130 | * making all this a pointless excercise. | ||
131 | */ | ||
132 | /* If we see that we are N usec away from whole second, | ||
133 | * we'll sleep for N-ADJ usecs. ADJ corrects for the fact | ||
134 | * that CPU is not infinitely fast. | ||
135 | * On infinitely fast CPU, next wakeup would be | ||
136 | * on (exactly_next_whole_second - ADJ). On real CPUs, | ||
137 | * this difference between current time and whole second | ||
138 | * is less than ADJ (assuming system isn't heavily loaded). | ||
139 | */ | ||
140 | /* Small value of 256us gives very precise sync for 2+ GHz CPUs. | ||
141 | * Slower CPUs will fail to sync and will go to bigger | ||
142 | * ADJ values. qemu-emulated armv4tl with ~100 MHz | ||
143 | * performance ends up using ADJ ~= 4*1024 and it takes | ||
144 | * 2+ secs (2 tries with successively larger ADJ) | ||
145 | * to sync. Even straced one on the same qemu (very slow) | ||
146 | * takes only 4 tries. | ||
147 | */ | ||
148 | #define TWEAK_USEC 256 | ||
149 | unsigned adj = TWEAK_USEC; | ||
150 | struct tm tm_time; | ||
151 | niro | 816 | struct timeval tv; |
152 | niro | 984 | int rtc = rtc_xopen(pp_rtcname, O_WRONLY); |
153 | niro | 532 | |
154 | niro | 984 | /* Try to catch the moment when whole second is close */ |
155 | while (1) { | ||
156 | unsigned rem_usec; | ||
157 | time_t t; | ||
158 | |||
159 | gettimeofday(&tv, NULL); | ||
160 | |||
161 | t = tv.tv_sec; | ||
162 | rem_usec = 1000000 - tv.tv_usec; | ||
163 | niro | 990 | if (rem_usec < adj) { |
164 | /* Close enough */ | ||
165 | niro | 984 | small_rem: |
166 | t++; | ||
167 | } | ||
168 | |||
169 | niro | 990 | /* Prepare tm_time from t */ |
170 | niro | 984 | if (utc) |
171 | gmtime_r(&t, &tm_time); /* may read /etc/xxx (it takes time) */ | ||
172 | else | ||
173 | localtime_r(&t, &tm_time); /* same */ | ||
174 | |||
175 | niro | 990 | if (adj >= 32*1024) { |
176 | break; /* 32 ms diff and still no luck?? give up trying to sync */ | ||
177 | } | ||
178 | |||
179 | niro | 984 | /* gmtime/localtime took some time, re-get cur time */ |
180 | gettimeofday(&tv, NULL); | ||
181 | |||
182 | niro | 990 | if (tv.tv_sec < t /* we are still in old second */ |
183 | || (tv.tv_sec == t && tv.tv_usec < adj) /* not too far into next second */ | ||
184 | niro | 984 | ) { |
185 | niro | 990 | break; /* good, we are in sync! */ |
186 | niro | 984 | } |
187 | niro | 990 | |
188 | rem_usec = 1000000 - tv.tv_usec; | ||
189 | if (rem_usec < adj) { | ||
190 | t = tv.tv_sec; | ||
191 | goto small_rem; /* already close to next sec, don't sleep */ | ||
192 | niro | 984 | } |
193 | |||
194 | /* Try to sync up by sleeping */ | ||
195 | niro | 990 | usleep(rem_usec - adj); |
196 | |||
197 | /* Jump to 1ms diff, then increase fast (x2): EVERY loop | ||
198 | * takes ~1 sec, people won't like slowly converging code here! | ||
199 | */ | ||
200 | //bb_error_msg("adj:%d tv.tv_usec:%d", adj, (int)tv.tv_usec); | ||
201 | if (adj < 512) | ||
202 | adj = 512; | ||
203 | /* ... and if last "overshoot" does not look insanely big, | ||
204 | * just use it as adj increment. This makes convergence faster. | ||
205 | */ | ||
206 | if (tv.tv_usec < adj * 8) { | ||
207 | adj += tv.tv_usec; | ||
208 | continue; | ||
209 | niro | 984 | } |
210 | niro | 990 | adj *= 2; |
211 | niro | 984 | } |
212 | niro | 990 | /* Debug aid to find "optimal" TWEAK_USEC with nearly exact sync. |
213 | * Look for a value which makes tv_usec close to 999999 or 0. | ||
214 | * For 2.20GHz Intel Core 2: optimal TWEAK_USEC ~= 200 | ||
215 | */ | ||
216 | //bb_error_msg("tv.tv_usec:%d", (int)tv.tv_usec); | ||
217 | #endif | ||
218 | niro | 984 | |
219 | niro | 990 | tm_time.tm_isdst = 0; |
220 | niro | 984 | xioctl(rtc, RTC_SET_TIME, &tm_time); |
221 | |||
222 | if (ENABLE_FEATURE_CLEAN_UP) | ||
223 | close(rtc); | ||
224 | niro | 532 | } |
225 | |||
226 | #define HWCLOCK_OPT_LOCALTIME 0x01 | ||
227 | #define HWCLOCK_OPT_UTC 0x02 | ||
228 | #define HWCLOCK_OPT_SHOW 0x04 | ||
229 | #define HWCLOCK_OPT_HCTOSYS 0x08 | ||
230 | #define HWCLOCK_OPT_SYSTOHC 0x10 | ||
231 | niro | 816 | #define HWCLOCK_OPT_RTCFILE 0x20 |
232 | niro | 532 | |
233 | niro | 816 | int hwclock_main(int argc, char **argv) MAIN_EXTERNALLY_VISIBLE; |
234 | int hwclock_main(int argc UNUSED_PARAM, char **argv) | ||
235 | niro | 532 | { |
236 | niro | 984 | const char *rtcname = NULL; |
237 | niro | 532 | unsigned opt; |
238 | int utc; | ||
239 | |||
240 | #if ENABLE_FEATURE_HWCLOCK_LONG_OPTIONS | ||
241 | niro | 816 | static const char hwclock_longopts[] ALIGN1 = |
242 | "localtime\0" No_argument "l" | ||
243 | "utc\0" No_argument "u" | ||
244 | "show\0" No_argument "r" | ||
245 | "hctosys\0" No_argument "s" | ||
246 | "systohc\0" No_argument "w" | ||
247 | "file\0" Required_argument "f" | ||
248 | ; | ||
249 | applet_long_options = hwclock_longopts; | ||
250 | niro | 532 | #endif |
251 | niro | 816 | opt_complementary = "r--ws:w--rs:s--wr:l--u:u--l"; |
252 | opt = getopt32(argv, "lurswf:", &rtcname); | ||
253 | niro | 532 | |
254 | /* If -u or -l wasn't given check if we are using utc */ | ||
255 | if (opt & (HWCLOCK_OPT_UTC | HWCLOCK_OPT_LOCALTIME)) | ||
256 | niro | 816 | utc = (opt & HWCLOCK_OPT_UTC); |
257 | niro | 532 | else |
258 | niro | 816 | utc = rtc_adjtime_is_utc(); |
259 | niro | 532 | |
260 | niro | 816 | if (opt & HWCLOCK_OPT_HCTOSYS) |
261 | niro | 984 | to_sys_clock(&rtcname, utc); |
262 | niro | 816 | else if (opt & HWCLOCK_OPT_SYSTOHC) |
263 | niro | 984 | from_sys_clock(&rtcname, utc); |
264 | niro | 816 | else |
265 | niro | 532 | /* default HWCLOCK_OPT_SHOW */ |
266 | niro | 984 | show_clock(&rtcname, utc); |
267 | niro | 816 | |
268 | return 0; | ||
269 | niro | 532 | } |