c259acab83
The ability to read the PHC (Physical Hardware Clock) alongside multiple system clocks is currently dependent on the specific hardware architecture. This limitation restricts the use of PTP_SYS_OFFSET_PRECISE to certain hardware configurations. The generic soultion which would work across all architectures is to read the PHC along with the latency to perform PHC-read as offered by PTP_SYS_OFFSET_EXTENDED which provides pre and post timestamps. However, these timestamps are currently limited to the CLOCK_REALTIME timebase. Since CLOCK_REALTIME is affected by NTP (or similar time synchronization services), it can experience significant jumps forward or backward. This hinders the precise latency measurements that PTP_SYS_OFFSET_EXTENDED is designed to provide. This problem could be addressed by supporting MONOTONIC_RAW timestamps within PTP_SYS_OFFSET_EXTENDED. Unlike CLOCK_REALTIME or CLOCK_MONOTONIC, the MONOTONIC_RAW timebase is unaffected by NTP adjustments. This enhancement can be implemented by utilizing one of the three reserved words within the PTP_SYS_OFFSET_EXTENDED struct to pass the clock-id for timestamps. The current behavior aligns with clock-id for CLOCK_REALTIME timebase (value of 0), ensuring backward compatibility of the UAPI. Signed-off-by: Mahesh Bandewar <maheshb@google.com> Signed-off-by: Vadim Fedorenko <vadfed@meta.com> Signed-off-by: David S. Miller <davem@davemloft.net> |
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| LICENSES | ||
| arch | ||
| block | ||
| certs | ||
| crypto | ||
| drivers | ||
| fs | ||
| include | ||
| init | ||
| io_uring | ||
| ipc | ||
| kernel | ||
| lib | ||
| mm | ||
| net | ||
| rust | ||
| samples | ||
| scripts | ||
| security | ||
| sound | ||
| tools | ||
| usr | ||
| virt | ||
| .clang-format | ||
| .cocciconfig | ||
| .editorconfig | ||
| .get_maintainer.ignore | ||
| .gitattributes | ||
| .gitignore | ||
| .mailmap | ||
| .rustfmt.toml | ||
| COPYING | ||
| CREDITS | ||
| Kbuild | ||
| Kconfig | ||
| MAINTAINERS | ||
| Makefile | ||
| README | ||
README
Linux kernel
============
There are several guides for kernel developers and users. These guides can
be rendered in a number of formats, like HTML and PDF. Please read
Documentation/admin-guide/README.rst first.
In order to build the documentation, use ``make htmldocs`` or
``make pdfdocs``. The formatted documentation can also be read online at:
https://www.kernel.org/doc/html/latest/
There are various text files in the Documentation/ subdirectory,
several of them using the reStructuredText markup notation.
Please read the Documentation/process/changes.rst file, as it contains the
requirements for building and running the kernel, and information about
the problems which may result by upgrading your kernel.