Miroslav Lichvar wrote: > The switch_interrupts() function should log an error message when the > driver doesn't support interrupts. Instead of adding more log messages > to explain the error, I'd prefer a new question in the FAQ > specifically for the error message.
The function switch_interrupts() does indeed currently log an error message when an error is detected; however, an error could occur when enabling or disabling interrupts, so this updated patch still produces a consolidated error message: "Interrupts not supported by RTC device /path/to/rtc" A new FAQ entry has been added for that particular error message. Also, if initialisation of chrony's RTC driver fails for any reason, a definitive warning is also still logged: "The RTC driver could not be initialised." To apply this patch, save this email to /path/to/email, and then run: git am --scissors /path/to/email Sincerely, Michael Witten --8<----8<----8<----8<----8<----8<----8<----8<----8<----8<----8<----8<----8<-- This commit updates the FAQ to point the user towards a solution; it also updates the RTC driver code (rtc_linux.c:RTC_Linux_Initialise()) to provide diagnostic messages that explicitly inform the user of a problem: * "Interrupts not supported by RTC device /path/to/rtc" * "The RTC driver could not be initialised." chrony's Linux RTC driver (rtc_linux.c) requires the following ioctl requests to be functional: RTC_UIE_ON RTC_UIE_OFF However, a Linux system's RTC driver does not necessarily implement them, as noted in these previous commits: d66b2f2b2423bfbd3de4d69895024dac7eefb306 rtc: handle RTCs that don't support interrupts Tue Dec 10 17:45:28 2019 +0100 bff3f51d13c3f41e2ead2cfff5bfe0b8c22ef44a rtc: extend check for RTCs that don't support interrupts Thu Dec 12 12:50:19 2019 +0100 Fortunately, the Linux kernel can be built with software emulation of these hardware requests, by enabling the following config variable: CONFIG_RTC_INTF_DEV_UIE_EMUL Provides an emulation for RTC_UIE if the underlying rtc chip driver does not expose RTC_UIE ioctls. Those requests generate once-per-second update interrupts, used for synchronization. The emulation code will read the time from the hardware clock several times per second, please enable this option only if you know that you really need it. This commit records these facts for the benefit of the user. --- doc/faq.adoc | 13 +++++++++++++ rtc_linux.c | 15 +++++++++++---- 2 files changed, 24 insertions(+), 4 deletions(-) diff --git a/doc/faq.adoc b/doc/faq.adoc index 9d2c109..74598be 100644 --- a/doc/faq.adoc +++ b/doc/faq.adoc @@ -597,6 +597,19 @@ things Some other program running on the system might be using the device. +=== When I start `chrony`, the log says `Interrupts not supported by RTC device` + +Your real-time clock hardware might not support the required ioctl requests: + +* `RTC_UIE_ON` +* `RTC_UIE_OFF` + +A possible solution might be to build the Linux kernel with support for software +emulation instead; try enabling the following configuration option when building +the Linux kernel: + +* `CONFIG_RTC_INTF_DEV_UIE_EMUL` + === What if my computer does not have an RTC or backup battery? In this case you can still use the `-s` option to set the system clock to the diff --git a/rtc_linux.c b/rtc_linux.c index 08c2a19..29c5a9f 100644 --- a/rtc_linux.c +++ b/rtc_linux.c @@ -507,18 +507,21 @@ switch_interrupts(int on_off) int RTC_Linux_Initialise(void) { + const char *const rtc_path = CNF_GetRtcDevice(); + /* Try to open the device */ - fd = open(CNF_GetRtcDevice(), O_RDWR); + fd = open(rtc_path, O_RDWR); if (fd < 0) { LOG(LOGS_ERR, "Could not open RTC device %s : %s", - CNF_GetRtcDevice(), strerror(errno)); - return 0; + rtc_path, strerror(errno)); + goto failure; } /* Make sure the RTC supports interrupts */ if (!switch_interrupts(1) || !switch_interrupts(0)) { close(fd); - return 0; + LOG(LOGS_ERR, "Interrupts not supported by RTC device %s", rtc_path); + goto failure; } /* Close on exec */ @@ -553,6 +556,10 @@ RTC_Linux_Initialise(void) " Date (UTC) Time RTC fast (s) Val Est fast (s) Slope (ppm) Ns Nr Meas") : -1; return 1; + +failure: + LOG(LOGS_WARN, "The RTC driver could not be initialised"); + return 0; } /* ================================================== */ -- 2.22.0 -- To unsubscribe email chrony-dev-requ...@chrony.tuxfamily.org with "unsubscribe" in the subject. For help email chrony-dev-requ...@chrony.tuxfamily.org with "help" in the subject. Trouble? Email listmas...@chrony.tuxfamily.org.