![Matt LaPlante](/assets/img/avatar_default.png)
Fix various typos in documentation txts. Signed-off-by: Matt LaPlante <kernel1@cyberdogtech.com> Signed-off-by: Jiri Kosina <jkosina@suse.cz>
300 lines
6.4 KiB
Text
300 lines
6.4 KiB
Text
High Precision Event Timer Driver for Linux
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The High Precision Event Timer (HPET) hardware follows a specification
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by Intel and Microsoft which can be found at
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http://www.intel.com/technology/architecture/hpetspec.htm
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Each HPET has one fixed-rate counter (at 10+ MHz, hence "High Precision")
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and up to 32 comparators. Normally three or more comparators are provided,
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each of which can generate oneshot interrupts and at least one of which has
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additional hardware to support periodic interrupts. The comparators are
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also called "timers", which can be misleading since usually timers are
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independent of each other ... these share a counter, complicating resets.
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HPET devices can support two interrupt routing modes. In one mode, the
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comparators are additional interrupt sources with no particular system
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role. Many x86 BIOS writers don't route HPET interrupts at all, which
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prevents use of that mode. They support the other "legacy replacement"
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mode where the first two comparators block interrupts from 8254 timers
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and from the RTC.
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The driver supports detection of HPET driver allocation and initialization
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of the HPET before the driver module_init routine is called. This enables
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platform code which uses timer 0 or 1 as the main timer to intercept HPET
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initialization. An example of this initialization can be found in
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arch/x86/kernel/hpet.c.
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The driver provides a userspace API which resembles the API found in the
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RTC driver framework. An example user space program is provided below.
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#include <stdio.h>
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#include <stdlib.h>
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#include <unistd.h>
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#include <fcntl.h>
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#include <string.h>
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#include <memory.h>
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#include <malloc.h>
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#include <time.h>
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#include <ctype.h>
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#include <sys/types.h>
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#include <sys/wait.h>
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#include <signal.h>
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#include <fcntl.h>
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#include <errno.h>
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#include <sys/time.h>
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#include <linux/hpet.h>
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extern void hpet_open_close(int, const char **);
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extern void hpet_info(int, const char **);
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extern void hpet_poll(int, const char **);
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extern void hpet_fasync(int, const char **);
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extern void hpet_read(int, const char **);
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#include <sys/poll.h>
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#include <sys/ioctl.h>
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#include <signal.h>
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struct hpet_command {
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char *command;
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void (*func)(int argc, const char ** argv);
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} hpet_command[] = {
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{
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"open-close",
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hpet_open_close
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},
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{
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"info",
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hpet_info
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},
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{
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"poll",
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hpet_poll
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},
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{
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"fasync",
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hpet_fasync
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},
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};
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int
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main(int argc, const char ** argv)
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{
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int i;
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argc--;
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argv++;
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if (!argc) {
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fprintf(stderr, "-hpet: requires command\n");
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return -1;
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}
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for (i = 0; i < (sizeof (hpet_command) / sizeof (hpet_command[0])); i++)
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if (!strcmp(argv[0], hpet_command[i].command)) {
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argc--;
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argv++;
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fprintf(stderr, "-hpet: executing %s\n",
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hpet_command[i].command);
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hpet_command[i].func(argc, argv);
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return 0;
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}
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fprintf(stderr, "do_hpet: command %s not implemented\n", argv[0]);
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return -1;
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}
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void
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hpet_open_close(int argc, const char **argv)
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{
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int fd;
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if (argc != 1) {
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fprintf(stderr, "hpet_open_close: device-name\n");
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return;
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}
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fd = open(argv[0], O_RDONLY);
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if (fd < 0)
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fprintf(stderr, "hpet_open_close: open failed\n");
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else
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close(fd);
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return;
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}
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void
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hpet_info(int argc, const char **argv)
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{
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}
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void
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hpet_poll(int argc, const char **argv)
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{
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unsigned long freq;
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int iterations, i, fd;
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struct pollfd pfd;
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struct hpet_info info;
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struct timeval stv, etv;
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struct timezone tz;
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long usec;
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if (argc != 3) {
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fprintf(stderr, "hpet_poll: device-name freq iterations\n");
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return;
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}
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freq = atoi(argv[1]);
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iterations = atoi(argv[2]);
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fd = open(argv[0], O_RDONLY);
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if (fd < 0) {
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fprintf(stderr, "hpet_poll: open of %s failed\n", argv[0]);
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return;
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}
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if (ioctl(fd, HPET_IRQFREQ, freq) < 0) {
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fprintf(stderr, "hpet_poll: HPET_IRQFREQ failed\n");
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goto out;
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}
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if (ioctl(fd, HPET_INFO, &info) < 0) {
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fprintf(stderr, "hpet_poll: failed to get info\n");
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goto out;
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}
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fprintf(stderr, "hpet_poll: info.hi_flags 0x%lx\n", info.hi_flags);
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if (info.hi_flags && (ioctl(fd, HPET_EPI, 0) < 0)) {
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fprintf(stderr, "hpet_poll: HPET_EPI failed\n");
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goto out;
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}
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if (ioctl(fd, HPET_IE_ON, 0) < 0) {
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fprintf(stderr, "hpet_poll, HPET_IE_ON failed\n");
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goto out;
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}
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pfd.fd = fd;
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pfd.events = POLLIN;
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for (i = 0; i < iterations; i++) {
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pfd.revents = 0;
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gettimeofday(&stv, &tz);
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if (poll(&pfd, 1, -1) < 0)
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fprintf(stderr, "hpet_poll: poll failed\n");
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else {
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long data;
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gettimeofday(&etv, &tz);
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usec = stv.tv_sec * 1000000 + stv.tv_usec;
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usec = (etv.tv_sec * 1000000 + etv.tv_usec) - usec;
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fprintf(stderr,
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"hpet_poll: expired time = 0x%lx\n", usec);
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fprintf(stderr, "hpet_poll: revents = 0x%x\n",
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pfd.revents);
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if (read(fd, &data, sizeof(data)) != sizeof(data)) {
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fprintf(stderr, "hpet_poll: read failed\n");
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}
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else
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fprintf(stderr, "hpet_poll: data 0x%lx\n",
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data);
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}
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}
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out:
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close(fd);
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return;
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}
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static int hpet_sigio_count;
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static void
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hpet_sigio(int val)
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{
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fprintf(stderr, "hpet_sigio: called\n");
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hpet_sigio_count++;
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}
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void
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hpet_fasync(int argc, const char **argv)
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{
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unsigned long freq;
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int iterations, i, fd, value;
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sig_t oldsig;
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struct hpet_info info;
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hpet_sigio_count = 0;
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fd = -1;
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if ((oldsig = signal(SIGIO, hpet_sigio)) == SIG_ERR) {
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fprintf(stderr, "hpet_fasync: failed to set signal handler\n");
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return;
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}
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if (argc != 3) {
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fprintf(stderr, "hpet_fasync: device-name freq iterations\n");
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goto out;
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}
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fd = open(argv[0], O_RDONLY);
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if (fd < 0) {
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fprintf(stderr, "hpet_fasync: failed to open %s\n", argv[0]);
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return;
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}
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if ((fcntl(fd, F_SETOWN, getpid()) == 1) ||
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((value = fcntl(fd, F_GETFL)) == 1) ||
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(fcntl(fd, F_SETFL, value | O_ASYNC) == 1)) {
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fprintf(stderr, "hpet_fasync: fcntl failed\n");
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goto out;
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}
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freq = atoi(argv[1]);
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iterations = atoi(argv[2]);
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if (ioctl(fd, HPET_IRQFREQ, freq) < 0) {
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fprintf(stderr, "hpet_fasync: HPET_IRQFREQ failed\n");
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goto out;
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}
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if (ioctl(fd, HPET_INFO, &info) < 0) {
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fprintf(stderr, "hpet_fasync: failed to get info\n");
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goto out;
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}
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fprintf(stderr, "hpet_fasync: info.hi_flags 0x%lx\n", info.hi_flags);
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if (info.hi_flags && (ioctl(fd, HPET_EPI, 0) < 0)) {
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fprintf(stderr, "hpet_fasync: HPET_EPI failed\n");
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goto out;
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}
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if (ioctl(fd, HPET_IE_ON, 0) < 0) {
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fprintf(stderr, "hpet_fasync, HPET_IE_ON failed\n");
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goto out;
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}
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for (i = 0; i < iterations; i++) {
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(void) pause();
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fprintf(stderr, "hpet_fasync: count = %d\n", hpet_sigio_count);
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}
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out:
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signal(SIGIO, oldsig);
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if (fd >= 0)
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close(fd);
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return;
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}
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