static acpi_status vmbus_walk_resources()

in vmbus_drv.c [2159:2262]

• 66 lines of code
• 15 McCabe index (conditional complexity)

static acpi_status vmbus_walk_resources(struct acpi_resource *res, void *ctx)
{
	resource_size_t start = 0;
	resource_size_t end = 0;
	struct resource *new_res;
	struct resource **old_res = &hyperv_mmio;
	struct resource **prev_res = NULL;
	struct resource r;

	switch (res->type) {

	/*
	 * "Address" descriptors are for bus windows. Ignore
	 * "memory" descriptors, which are for registers on
	 * devices.
	 */
	case ACPI_RESOURCE_TYPE_ADDRESS32:
		start = res->data.address32.address.minimum;
		end = res->data.address32.address.maximum;
		break;

	case ACPI_RESOURCE_TYPE_ADDRESS64:
		start = res->data.address64.address.minimum;
		end = res->data.address64.address.maximum;
		break;

	/*
	 * The IRQ information is needed only on ARM64, which Hyper-V
	 * sets up in the extended format. IRQ information is present
	 * on x86/x64 in the non-extended format but it is not used by
	 * Linux. So don't bother checking for the non-extended format.
	 */
	case ACPI_RESOURCE_TYPE_EXTENDED_IRQ:
		if (!acpi_dev_resource_interrupt(res, 0, &r)) {
			pr_err("Unable to parse Hyper-V ACPI interrupt\n");
			return AE_ERROR;
		}
		/* ARM64 INTID for VMbus */
		vmbus_interrupt = res->data.extended_irq.interrupts[0];
		/* Linux IRQ number */
		vmbus_irq = r.start;
		return AE_OK;

	default:
		/* Unused resource type */
		return AE_OK;

	}
	/*
	 * Ignore ranges that are below 1MB, as they're not
	 * necessary or useful here.
	 */
	if (end < 0x100000)
		return AE_OK;

	new_res = kzalloc(sizeof(*new_res), GFP_ATOMIC);
	if (!new_res)
		return AE_NO_MEMORY;

	/* If this range overlaps the virtual TPM, truncate it. */
	if (end > VTPM_BASE_ADDRESS && start < VTPM_BASE_ADDRESS)
		end = VTPM_BASE_ADDRESS;

	new_res->name = "hyperv mmio";
	new_res->flags = IORESOURCE_MEM;
	new_res->start = start;
	new_res->end = end;

	/*
	 * If two ranges are adjacent, merge them.
	 */
	do {
		if (!*old_res) {
			*old_res = new_res;
			break;
		}

		if (((*old_res)->end + 1) == new_res->start) {
			(*old_res)->end = new_res->end;
			kfree(new_res);
			break;
		}

		if ((*old_res)->start == new_res->end + 1) {
			(*old_res)->start = new_res->start;
			kfree(new_res);
			break;
		}

		if ((*old_res)->start > new_res->end) {
			new_res->sibling = *old_res;
			if (prev_res)
				(*prev_res)->sibling = new_res;
			*old_res = new_res;
			break;
		}

		prev_res = old_res;
		old_res = &(*old_res)->sibling;

	} while (1);

	return AE_OK;
}