arch/um/drivers/rtc_user.c

File Facts

System

Linux kernel

Corpus path

arch/um/drivers/rtc_user.c

Extension

.c

Size

1512 bytes

Lines

82

Domain

Architecture Layer

Bucket

arch/um

Inferred role

Architecture Layer: implementation source

Status

source implementation candidate

Why This File Exists

CPU and platform-specific kernel glue: boot entry, traps, syscall entry, interrupts, page tables, context switch, and low-level barriers.

• CPU and platform-specific kernel glue: boot entry, traps, syscall entry, interrupts, page tables, context switch, and low-level barriers.
• Defines or uses C structs; map object ownership, embedded links, reference counts, and lock ownership.

Dependency Surface

• stdbool.h
• os.h
• errno.h
• sched.h
• unistd.h
• kern_util.h
• sys/select.h
• stdio.h
• sys/timerfd.h
• rtc.h

Detected Declarations

• function uml_rtc_send_timetravel_alarm
• function uml_rtc_start
• function uml_rtc_enable_alarm
• function uml_rtc_disable_alarm
• function uml_rtc_stop

Annotated Snippet

if (uml_rtc_irq_fds[0] < 0) {
			err = -errno;
			goto fail;
		}

		/* apparently timerfd won't send SIGIO, use workaround */
		sigio_broken();
		err = add_sigio_fd(uml_rtc_irq_fds[0]);
		if (err < 0) {
			close(uml_rtc_irq_fds[0]);
			goto fail;
		}
	}

	return uml_rtc_irq_fds[0];
fail:
	uml_rtc_stop(timetravel);
	return err;
}

int uml_rtc_enable_alarm(unsigned long long delta_seconds)
{
	struct itimerspec it = {
		.it_value = {
			.tv_sec = delta_seconds,
		},
	};

	if (timerfd_settime(uml_rtc_irq_fds[0], 0, &it, NULL))
		return -errno;
	return 0;
}

void uml_rtc_disable_alarm(void)
{
	uml_rtc_enable_alarm(0);
}

void uml_rtc_stop(bool timetravel)
{
	if (timetravel)
		os_close_file(uml_rtc_irq_fds[1]);
	else
		ignore_sigio_fd(uml_rtc_irq_fds[0]);
	os_close_file(uml_rtc_irq_fds[0]);
}

Annotation

• Immediate include surface: `stdbool.h`, `os.h`, `errno.h`, `sched.h`, `unistd.h`, `kern_util.h`, `sys/select.h`, `stdio.h`.
• Detected declarations: `function uml_rtc_send_timetravel_alarm`, `function uml_rtc_start`, `function uml_rtc_enable_alarm`, `function uml_rtc_disable_alarm`, `function uml_rtc_stop`.
• Atlas domain: Architecture Layer / arch/um.
• Implementation status: source implementation candidate.

Implementation Notes

• This generated page is the file-by-file coverage layer; curated subsystem chapters should link here when they synthesize a multi-file control flow.
• Core OS pages should be promoted from atlas-only to deep-reviewed when they explain data structures, invariants, locking, lifecycle, and C implementation snippets.
• Driver-family pages are intentionally pattern-oriented unless they are part of the selected PCIe/NVMe representative device path.