static int __hw_perf_event_init()

in kernel/perf_cpum_cf.c [437:517]

• 57 lines of code
• 22 McCabe index (conditional complexity)

static int __hw_perf_event_init(struct perf_event *event, unsigned int type)
{
	struct perf_event_attr *attr = &event->attr;
	struct hw_perf_event *hwc = &event->hw;
	enum cpumf_ctr_set set;
	int err = 0;
	u64 ev;

	switch (type) {
	case PERF_TYPE_RAW:
		/* Raw events are used to access counters directly,
		 * hence do not permit excludes */
		if (attr->exclude_kernel || attr->exclude_user ||
		    attr->exclude_hv)
			return -EOPNOTSUPP;
		ev = attr->config;
		break;

	case PERF_TYPE_HARDWARE:
		if (is_sampling_event(event))	/* No sampling support */
			return -ENOENT;
		ev = attr->config;
		/* Count user space (problem-state) only */
		if (!attr->exclude_user && attr->exclude_kernel) {
			if (ev >= ARRAY_SIZE(cpumf_generic_events_user))
				return -EOPNOTSUPP;
			ev = cpumf_generic_events_user[ev];

		/* No support for kernel space counters only */
		} else if (!attr->exclude_kernel && attr->exclude_user) {
			return -EOPNOTSUPP;
		} else {	/* Count user and kernel space */
			if (ev >= ARRAY_SIZE(cpumf_generic_events_basic))
				return -EOPNOTSUPP;
			ev = cpumf_generic_events_basic[ev];
		}
		break;

	default:
		return -ENOENT;
	}

	if (ev == -1)
		return -ENOENT;

	if (ev > PERF_CPUM_CF_MAX_CTR)
		return -ENOENT;

	/* Obtain the counter set to which the specified counter belongs */
	set = get_counter_set(ev);
	switch (set) {
	case CPUMF_CTR_SET_BASIC:
	case CPUMF_CTR_SET_USER:
	case CPUMF_CTR_SET_CRYPTO:
	case CPUMF_CTR_SET_EXT:
	case CPUMF_CTR_SET_MT_DIAG:
		/*
		 * Use the hardware perf event structure to store the
		 * counter number in the 'config' member and the counter
		 * set number in the 'config_base' as bit mask.
		 * It is later used to enable/disable the counter(s).
		 */
		hwc->config = ev;
		hwc->config_base = cpumf_ctr_ctl[set];
		break;
	case CPUMF_CTR_SET_MAX:
		/* The counter could not be associated to a counter set */
		return -EINVAL;
	}

	/* Initialize for using the CPU-measurement counter facility */
	cpumf_hw_inuse();
	event->destroy = hw_perf_event_destroy;

	/* Finally, validate version and authorization of the counter set */
	err = validate_ctr_auth(hwc);
	if (!err)
		err = validate_ctr_version(hwc, set);

	return err;
}