This patch extends CLOCKFD support to clock_getres(), allowing
applications to query the resolution of PTP clocks through file
descriptors using the standard POSIX clock API.
Key changes include:
1. Move clock_getres() from libc to kernel:
- Relocated from libs/libc/sched/clock_getres.c to sched/clock/
- Enables direct kernel-level file descriptor handling
- Maintains POSIX compliance while adding CLOCKFD support
2. CLOCKFD support in clock_getres():
- Detects CLOCKFD-encoded clockids using CLOCKFD_TO_FD() check
- Extracts file descriptor from clockid parameter
- Validates file descriptor through fs_getfilep()
- Issues PTP_CLOCK_GETRES ioctl to query clock resolution
3. PTP clock resolution query:
- Retrieves resolution from PTP clock device via ioctl
- Returns nanosecond-precision timing resolution
- Enables applications to determine clock accuracy capabilities
- Falls back to standard clock resolution for non-CLOCKFD clockids
4. Error handling:
- Returns EINVAL for invalid CLOCKFD file descriptors
- Properly manages file reference counting with fs_putfilep()
- Maintains backward compatibility with existing clock types
5. Build system updates:
- Updated libs/libc/sched/CMakeLists.txt and Make.defs
- Updated sched/clock/CMakeLists.txt to include clock_getres.c
- Ensures proper compilation in kernel context
Usage example:
int fd = open("/dev/ptp0", O_RDONLY);
struct timespec res;
clock_getres(CLOCKFD(fd), &res); /* Query PTP clock resolution */
printf("Resolution: %ld.%09ld sec\n", res.tv_sec, res.tv_nsec);
close(fd);
This completes the basic POSIX clock API support for dynamic PTP clocks,
providing applications with comprehensive clock information access.
Signed-off-by: dongjiuzhu1 <dongjiuzhu1@xiaomi.com>
here is the reason:
1.clock_systime_timespec(core function) always exist regardless the setting
2.CLOCK_MONOTONIC is a foundamental clock type required by many places
Signed-off-by: Xiang Xiao <xiaoxiang@xiaomi.com>
