static const struct k_clock *clockid_to_kclock(const clockid_t id)
{
clockid_t idx = id;
if (id < 0) {
return (id & CLOCKFD_MASK) == CLOCKFD ?
&clock_posix_dynamic : &clock_posix_cpu;
}
if (id >= ARRAY_SIZE(posix_clocks))
return NULL;
return posix_clocks[array_index_nospec(idx, ARRAY_SIZE(posix_clocks))];
}
static const struct k_clock * const posix_clocks[] = {
[CLOCK_REALTIME] = &clock_realtime,
[CLOCK_MONOTONIC] = &clock_monotonic,
[CLOCK_PROCESS_CPUTIME_ID] = &clock_process,
[CLOCK_THREAD_CPUTIME_ID] = &clock_thread,
[CLOCK_MONOTONIC_RAW] = &clock_monotonic_raw,
[CLOCK_REALTIME_COARSE] = &clock_realtime_coarse,
[CLOCK_MONOTONIC_COARSE] = &clock_monotonic_coarse,
[CLOCK_BOOTTIME] = &clock_boottime,
[CLOCK_REALTIME_ALARM] = &alarm_clock,
[CLOCK_BOOTTIME_ALARM] = &alarm_clock,
[CLOCK_TAI] = &clock_tai,
};
const struct k_clock clock_posix_dynamic = {
.clock_getres = pc_clock_getres,
.clock_set = pc_clock_settime,
.clock_get = pc_clock_gettime,
.clock_adj = pc_clock_adjtime,
};
static int pc_clock_gettime(clockid_t id, struct timespec64 *ts)
{
struct posix_clock_desc cd;
int err;
err = get_clock_desc(id, &cd);
if (err)
return err;
if (cd.clk->ops.clock_gettime)
err = cd.clk->ops.clock_gettime(cd.clk, ts);
else
err = -EOPNOTSUPP;
put_clock_desc(&cd);
return err;
}
static int get_clock_desc(const clockid_t id, struct posix_clock_desc cd)
{
struct file fp = fget(clockid_to_fd(id));
int err = -EINVAL;
if (!fp)
return err;
if (fp->f_op->open != posix_clock_open || !fp->private_data)
goto out;
cd->fp = fp;
cd->clk = get_posix_clock(fp);
err = cd->clk ? 0 : -ENODEV;
out:
if (err)
fput(fp);
return err;
}
static inline int clockid_to_fd(const clockid_t clk)
{
return ~(clk >> 3);
}
struct file *fget(unsigned int fd)
{
return __fget(fd, FMODE_PATH, 1);
}
static struct file __fget(unsigned int fd, fmode_t mask, unsigned int refs)
{
struct files_struct files = current->files;
struct file *file;
rcu_read_lock();
loop:
file = fcheck_files(files, fd);
if (file) {
/* File object ref couldn’t be taken.
- dup2() atomicity guarantee is the reason
- we loop to catch the new file (or NULL pointer)
*/
if (file->f_mode & mask)
file = NULL;
else if (!get_file_rcu_many(file, refs))
goto loop;
}
rcu_read_unlock();
return file;
}
static struct posix_clock get_posix_clock(struct file fp)
{
struct posix_clock *clk =fp->private_data;
down_read(&clk->rwsem);
if (!clk->zombie)
return clk;
up_read(&clk->rwsem);
return NULL;
}
app:
define CLOCKFD 3
define FD_TO_CLOCKID(fd) ((clockid_t) ((((unsigned int) ~fd) << 3) | CLOCKFD))
time_fd = open(“/dev/ptp0”, O_RDONLY);
struct timespec tp;
clock_gettime(FD_TO_CLOCKID(time_fd), &tp);
Original: https://blog.csdn.net/wmzjzwlzs/article/details/127814988
Author: wmzjzwlzs
Title: clockid_to_kclock
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