2 * rtc.c - Use /dev/rtc for clock access
10 #include <sys/select.h>
20 * Get defines for rtc stuff.
22 * Getting the rtc defines is nontrivial. The obvious way is by including
23 * <linux/mc146818rtc.h> but that again includes <asm/io.h> which again
24 * includes ... and on sparc and alpha this gives compilation errors for
25 * many kernel versions. So, we give the defines ourselves here. Moreover,
26 * some Sparc person decided to be incompatible, and used a struct rtc_time
27 * different from that used in mc146818rtc.h.
31 * On Sparcs, there is a <asm/rtc.h> that defines different ioctls (that are
32 * required on my machine). However, this include file does not exist on
33 * other architectures.
41 /* The following is roughly equivalent */
44 int sec
; /* Seconds 0-59 */
45 int min
; /* Minutes 0-59 */
46 int hour
; /* Hour 0-23 */
47 int dow
; /* Day of the week 1-7 */
48 int dom
; /* Day of the month 1-31 */
49 int month
; /* Month of year 1-12 */
50 int year
; /* Year 0-99 */
52 #define RTCGET _IOR('p', 20, struct sparc_rtc_time)
53 #define RTCSET _IOW('p', 21, struct sparc_rtc_time)
57 * struct rtc_time is present since 1.3.99.
58 * Earlier (since 1.3.89), a struct tm was used.
60 struct linux_rtc_time
{
72 /* RTC_RD_TIME etc have this definition since 1.99.9 (pre2.0-9) */
74 # define RTC_RD_TIME _IOR('p', 0x09, struct linux_rtc_time)
75 # define RTC_SET_TIME _IOW('p', 0x0a, struct linux_rtc_time)
76 # define RTC_UIE_ON _IO('p', 0x03) /* Update int. enable on */
77 # define RTC_UIE_OFF _IO('p', 0x04) /* Update int. enable off */
80 /* RTC_EPOCH_READ and RTC_EPOCH_SET are present since 2.0.34 and 2.1.89 */
81 #ifndef RTC_EPOCH_READ
82 # define RTC_EPOCH_READ _IOR('p', 0x0d, unsigned long) /* Read epoch */
83 # define RTC_EPOCH_SET _IOW('p', 0x0e, unsigned long) /* Set epoch */
87 * /dev/rtc is conventionally chardev 10/135
88 * ia64 uses /dev/efirtc, chardev 10/136
89 * devfs (obsolete) used /dev/misc/... for miscdev
90 * new RTC framework + udev uses dynamic major and /dev/rtc0.../dev/rtcN
91 * ... so we need an overridable default
94 /* default or user defined dev (by hwclock --rtc=<path>) */
95 static const char *rtc_dev_name
;
96 static int rtc_dev_fd
= -1;
98 static void close_rtc(void)
100 if (rtc_dev_fd
!= -1)
105 static int open_rtc(const struct hwclock_control
*ctl
)
107 static const char *fls
[] = {
118 if (rtc_dev_fd
!= -1)
121 /* --rtc option has been given */
122 if (ctl
->rtc_dev_name
) {
123 rtc_dev_name
= ctl
->rtc_dev_name
;
124 rtc_dev_fd
= open(rtc_dev_name
, O_RDONLY
);
126 for (i
= 0; i
< ARRAY_SIZE(fls
); i
++) {
128 printf(_("Trying to open: %s\n"), fls
[i
]);
129 rtc_dev_fd
= open(fls
[i
], O_RDONLY
);
132 && (errno
== ENOENT
|| errno
== ENODEV
))
134 rtc_dev_name
= fls
[i
];
138 rtc_dev_name
= *fls
; /* default for error messages */
140 if (rtc_dev_fd
!= -1)
145 static int open_rtc_or_exit(const struct hwclock_control
*ctl
)
147 int rtc_fd
= open_rtc(ctl
);
150 warn(_("cannot open rtc device"));
151 hwclock_exit(ctl
, EXIT_FAILURE
);
156 static int do_rtc_read_ioctl(int rtc_fd
, struct tm
*tm
)
161 /* some but not all sparcs use a different ioctl and struct */
162 struct sparc_rtc_time stm
;
165 ioctlname
= "RTC_RD_TIME";
166 rc
= ioctl(rtc_fd
, RTC_RD_TIME
, tm
);
169 if (rc
== -1) { /* sparc sbus */
170 ioctlname
= "RTCGET";
171 rc
= ioctl(rtc_fd
, RTCGET
, &stm
);
173 tm
->tm_sec
= stm
.sec
;
174 tm
->tm_min
= stm
.min
;
175 tm
->tm_hour
= stm
.hour
;
176 tm
->tm_mday
= stm
.dom
;
177 tm
->tm_mon
= stm
.month
- 1;
178 tm
->tm_year
= stm
.year
- 1900;
179 tm
->tm_wday
= stm
.dow
- 1;
180 tm
->tm_yday
= -1; /* day in the year */
186 warn(_("ioctl(%s) to %s to read the time failed"),
187 ioctlname
, rtc_dev_name
);
191 tm
->tm_isdst
= -1; /* don't know whether it's dst */
196 * Wait for the top of a clock tick by reading /dev/rtc in a busy loop
197 * until we see it. This function is used for rtc drivers without ioctl
198 * interrupts. This is typical on an Alpha, where the Hardware Clock
199 * interrupts are used by the kernel for the system clock, so aren't at
200 * the user's disposal.
202 static int busywait_for_rtc_clock_tick(const struct hwclock_control
*ctl
,
205 struct tm start_time
;
206 /* The time when we were called (and started waiting) */
209 struct timeval begin
, now
;
212 printf("ioctl(%d, RTC_UIE_ON, 0): %s\n",
213 rtc_fd
, strerror(errno
));
214 printf(_("Waiting in loop for time from %s to change\n"),
218 if (do_rtc_read_ioctl(rtc_fd
, &start_time
))
222 * Wait for change. Should be within a second, but in case
223 * something weird happens, we have a time limit (1.5s) on this loop
224 * to reduce the impact of this failure.
226 gettimeofday(&begin
, NULL
);
228 rc
= do_rtc_read_ioctl(rtc_fd
, &nowtime
);
229 if (rc
|| start_time
.tm_sec
!= nowtime
.tm_sec
)
231 gettimeofday(&now
, NULL
);
232 if (time_diff(now
, begin
) > 1.5) {
233 warnx(_("Timed out waiting for time change."));
244 * Same as synchronize_to_clock_tick(), but just for /dev/rtc.
246 static int synchronize_to_clock_tick_rtc(const struct hwclock_control
*ctl
)
248 int rtc_fd
; /* File descriptor of /dev/rtc */
251 rtc_fd
= open_rtc(ctl
);
253 warn(_("cannot open rtc device"));
256 /* Turn on update interrupts (one per second) */
257 int rc
= ioctl(rtc_fd
, RTC_UIE_ON
, 0);
261 * Just reading rtc_fd fails on broken hardware: no
262 * update interrupt comes and a bootscript with a
269 * Wait up to ten seconds for the next update
273 FD_SET(rtc_fd
, &rfds
);
276 rc
= select(rtc_fd
+ 1, &rfds
, NULL
, NULL
, &tv
);
280 warnx(_("select() to %s to wait for clock tick timed out"),
283 warn(_("select() to %s to wait for clock tick failed"),
285 /* Turn off update interrupts */
286 rc
= ioctl(rtc_fd
, RTC_UIE_OFF
, 0);
288 warn(_("ioctl() to %s to turn off update interrupts failed"),
290 } else if (errno
== ENOTTY
|| errno
== EINVAL
) {
291 /* rtc ioctl interrupts are unimplemented */
292 ret
= busywait_for_rtc_clock_tick(ctl
, rtc_fd
);
294 warn(_("ioctl(%d, RTC_UIE_ON, 0) to %s failed"),
295 rtc_fd
, rtc_dev_name
);
300 static int read_hardware_clock_rtc(const struct hwclock_control
*ctl
,
305 rtc_fd
= open_rtc_or_exit(ctl
);
307 /* Read the RTC time/date, return answer via tm */
308 rc
= do_rtc_read_ioctl(rtc_fd
, tm
);
314 * Set the Hardware Clock to the broken down time <new_broken_time>. Use
315 * ioctls to "rtc" device /dev/rtc.
317 static int set_hardware_clock_rtc(const struct hwclock_control
*ctl
,
318 const struct tm
*new_broken_time
)
324 rtc_fd
= open_rtc_or_exit(ctl
);
326 ioctlname
= "RTC_SET_TIME";
327 rc
= ioctl(rtc_fd
, RTC_SET_TIME
, new_broken_time
);
330 if (rc
== -1) { /* sparc sbus */
331 struct sparc_rtc_time stm
;
333 stm
.sec
= new_broken_time
->tm_sec
;
334 stm
.min
= new_broken_time
->tm_min
;
335 stm
.hour
= new_broken_time
->tm_hour
;
336 stm
.dom
= new_broken_time
->tm_mday
;
337 stm
.month
= new_broken_time
->tm_mon
+ 1;
338 stm
.year
= new_broken_time
->tm_year
+ 1900;
339 stm
.dow
= new_broken_time
->tm_wday
+ 1;
341 ioctlname
= "RTCSET";
342 rc
= ioctl(rtc_fd
, RTCSET
, &stm
);
347 warn(_("ioctl(%s) to %s to set the time failed"),
348 ioctlname
, rtc_dev_name
);
349 hwclock_exit(ctl
, EXIT_FAILURE
);
353 printf(_("ioctl(%s) was successful.\n"), ioctlname
);
358 static int get_permissions_rtc(void)
363 static const char *get_device_path(void)
368 static struct clock_ops rtc_interface
= {
369 N_("Using the rtc interface to the clock."),
371 read_hardware_clock_rtc
,
372 set_hardware_clock_rtc
,
373 synchronize_to_clock_tick_rtc
,
377 /* return &rtc if /dev/rtc can be opened, NULL otherwise */
378 struct clock_ops
*probe_for_rtc_clock(const struct hwclock_control
*ctl
)
380 const int rtc_fd
= open_rtc(ctl
);
384 return &rtc_interface
;
389 * Get the Hardware Clock epoch setting from the kernel.
391 int get_epoch_rtc(const struct hwclock_control
*ctl
, unsigned long *epoch_p
)
395 rtc_fd
= open_rtc(ctl
);
397 warn(_("cannot open %s"), rtc_dev_name
);
401 if (ioctl(rtc_fd
, RTC_EPOCH_READ
, epoch_p
) == -1) {
402 warn(_("ioctl(%d, RTC_EPOCH_READ, epoch_p) to %s failed"),
403 rtc_fd
, rtc_dev_name
);
408 printf(_("ioctl(%d, RTC_EPOCH_READ, epoch_p) to %s succeeded.\n"),
409 rtc_fd
, rtc_dev_name
);
415 * Set the Hardware Clock epoch in the kernel.
417 int set_epoch_rtc(const struct hwclock_control
*ctl
)
422 epoch
= strtoul(ctl
->epoch_option
, NULL
, 10);
424 /* There were no RTC clocks before 1900. */
425 if (epoch
< 1900 || epoch
== ULONG_MAX
) {
426 warnx(_("invalid epoch '%s'."), ctl
->epoch_option
);
430 rtc_fd
= open_rtc(ctl
);
432 warn(_("cannot open %s"), rtc_dev_name
);
436 if (ioctl(rtc_fd
, RTC_EPOCH_SET
, epoch
) == -1) {
437 warn(_("ioctl(%d, RTC_EPOCH_SET, %lu) to %s failed"),
438 rtc_fd
, epoch
, rtc_dev_name
);
443 printf(_("ioctl(%d, RTC_EPOCH_SET, %lu) to %s succeeded.\n"),
444 rtc_fd
, epoch
, rtc_dev_name
);
448 #endif /* __alpha__ */