the system clock from the discrete RTC, but use the integrated one for all
other tasks, because of its greater functionality.
+SYSFS INTERFACE
+---------------
+
+The sysfs interface under /sys/class/rtc/rtcN provides access to various
+rtc attributes without requiring the use of ioctls. All dates and times
+are in the RTC's timezone, rather than in system time.
+
+date: RTC-provided date
+hctosys: 1 if the RTC provided the system time at boot via the
+ CONFIG_RTC_HCTOSYS kernel option, 0 otherwise
+max_user_freq: The maximum interrupt rate an unprivileged user may request
+ from this RTC.
+name: The name of the RTC corresponding to this sysfs directory
+since_epoch: The number of seconds since the epoch according to the RTC
+time: RTC-provided time
+wakealarm: The time at which the clock will generate a system wakeup
+ event. This is a one shot wakeup event, so must be reset
+ after wake if a daily wakeup is required. Format is either
+ seconds since the epoch or, if there's a leading +, seconds
+ in the future.
+
+IOCTL INTERFACE
+---------------
+
The ioctl() calls supported by /dev/rtc are also supported by the RTC class
framework. However, because the chips and systems are not standardized,
some PC/AT functionality might not be provided. And in the same way, some
* RTC_AIE_ON, RTC_AIE_OFF, RTC_ALM_SET, RTC_ALM_READ ... when the RTC
is connected to an IRQ line, it can often issue an alarm IRQ up to
- 24 hours in the future.
+ 24 hours in the future. (Use RTC_WKALM_* by preference.)
* RTC_WKALM_SET, RTC_WKALM_RD ... RTCs that can issue alarms beyond
the next 24 hours use a slightly more powerful API, which supports
setting the longer alarm time and enabling its IRQ using a single
request (using the same model as EFI firmware).
- * RTC_UIE_ON, RTC_UIE_OFF ... if the RTC offers IRQs, it probably
- also offers update IRQs whenever the "seconds" counter changes.
- If needed, the RTC framework can emulate this mechanism.
+ * RTC_UIE_ON, RTC_UIE_OFF ... if the RTC offers IRQs, the RTC framework
+ will emulate this mechanism.
- * RTC_PIE_ON, RTC_PIE_OFF, RTC_IRQP_SET, RTC_IRQP_READ ... another
- feature often accessible with an IRQ line is a periodic IRQ, issued
- at settable frequencies (usually 2^N Hz).
+ * RTC_PIE_ON, RTC_PIE_OFF, RTC_IRQP_SET, RTC_IRQP_READ ... these icotls
+ are emulated via a kernel hrtimer.
In many cases, the RTC alarm can be a system wake event, used to force
Linux out of a low power sleep state (or hibernation) back to a fully
operational state. For example, a system could enter a deep power saving
state until it's time to execute some scheduled tasks.
-Note that many of these ioctls need not actually be implemented by your
-driver. The common rtc-dev interface handles many of these nicely if your
-driver returns ENOIOCTLCMD. Some common examples:
+Note that many of these ioctls are handled by the common rtc-dev interface.
+Some common examples:
* RTC_RD_TIME, RTC_SET_TIME: the read_time/set_time functions will be
called with appropriate values.
- * RTC_ALM_SET, RTC_ALM_READ, RTC_WKALM_SET, RTC_WKALM_RD: the
- set_alarm/read_alarm functions will be called. To differentiate
- between the ALM and WKALM, check the larger fields of the rtc_wkalrm
- struct (like tm_year). These will be set to -1 when using ALM and
- will be set to proper values when using WKALM.
+ * RTC_ALM_SET, RTC_ALM_READ, RTC_WKALM_SET, RTC_WKALM_RD: gets or sets
+ the alarm rtc_timer. May call the set_alarm driver function.
+
+ * RTC_IRQP_SET, RTC_IRQP_READ: These are emulated by the generic code.
- * RTC_IRQP_SET, RTC_IRQP_READ: the irq_set_freq function will be called
- to set the frequency while the framework will handle the read for you
- since the frequency is stored in the irq_freq member of the rtc_device
- structure. Also make sure you set the max_user_freq member in your
- initialization routines so the framework can sanity check the user
- input for you.
+ * RTC_PIE_ON, RTC_PIE_OFF: These are also emulated by the generic code.
If all else fails, check out the rtc-test.c driver!
/* This read will block */
retval = read(fd, &data, sizeof(unsigned long));
if (retval == -1) {
- perror("read");
- exit(errno);
+ perror("read");
+ exit(errno);
}
fprintf(stderr, " %d",i);
fflush(stderr);
rtc_tm.tm_sec %= 60;
rtc_tm.tm_min++;
}
- if (rtc_tm.tm_min == 60) {
+ if (rtc_tm.tm_min == 60) {
rtc_tm.tm_min = 0;
rtc_tm.tm_hour++;
}
- if (rtc_tm.tm_hour == 24)
+ if (rtc_tm.tm_hour == 24)
rtc_tm.tm_hour = 0;
retval = ioctl(fd, RTC_ALM_SET, &rtc_tm);
/* not all RTCs support periodic IRQs */
if (errno == ENOTTY) {
fprintf(stderr, "\nNo periodic IRQ support\n");
- return 0;
+ goto done;
}
perror("RTC_IRQP_READ ioctl");
exit(errno);
"\n...Periodic IRQ rate is fixed\n");
goto done;
}
- perror("RTC_IRQP_SET ioctl");
- exit(errno);
+ perror("RTC_IRQP_SET ioctl");
+ exit(errno);
}
fprintf(stderr, "\n%ldHz:\t", tmp);
/* Enable periodic interrupts */
retval = ioctl(fd, RTC_PIE_ON, 0);
if (retval == -1) {
- perror("RTC_PIE_ON ioctl");
- exit(errno);
+ perror("RTC_PIE_ON ioctl");
+ exit(errno);
}
for (i=1; i<21; i++) {
- /* This blocks */
- retval = read(fd, &data, sizeof(unsigned long));
- if (retval == -1) {
- perror("read");
- exit(errno);
- }
- fprintf(stderr, " %d",i);
- fflush(stderr);
- irqcount++;
+ /* This blocks */
+ retval = read(fd, &data, sizeof(unsigned long));
+ if (retval == -1) {
+ perror("read");
+ exit(errno);
+ }
+ fprintf(stderr, " %d",i);
+ fflush(stderr);
+ irqcount++;
}
/* Disable periodic interrupts */
retval = ioctl(fd, RTC_PIE_OFF, 0);
if (retval == -1) {
- perror("RTC_PIE_OFF ioctl");
- exit(errno);
+ perror("RTC_PIE_OFF ioctl");
+ exit(errno);
}
}
projects / linux-flexiantxendom0.git / blobdiff