int vp_modern_probe()

in virtio_pci_modern_dev.c [207:344]

• 103 lines of code
• 16 McCabe index (conditional complexity)

int vp_modern_probe(struct virtio_pci_modern_device *mdev)
{
	struct pci_dev *pci_dev = mdev->pci_dev;
	int err, common, isr, notify, device;
	u32 notify_length;
	u32 notify_offset;

	check_offsets();

	mdev->pci_dev = pci_dev;

	/* We only own devices >= 0x1000 and <= 0x107f: leave the rest. */
	if (pci_dev->device < 0x1000 || pci_dev->device > 0x107f)
		return -ENODEV;

	if (pci_dev->device < 0x1040) {
		/* Transitional devices: use the PCI subsystem device id as
		 * virtio device id, same as legacy driver always did.
		 */
		mdev->id.device = pci_dev->subsystem_device;
	} else {
		/* Modern devices: simply use PCI device id, but start from 0x1040. */
		mdev->id.device = pci_dev->device - 0x1040;
	}
	mdev->id.vendor = pci_dev->subsystem_vendor;

	/* check for a common config: if not, use legacy mode (bar 0). */
	common = virtio_pci_find_capability(pci_dev, VIRTIO_PCI_CAP_COMMON_CFG,
					    IORESOURCE_IO | IORESOURCE_MEM,
					    &mdev->modern_bars);
	if (!common) {
		dev_info(&pci_dev->dev,
			 "virtio_pci: leaving for legacy driver\n");
		return -ENODEV;
	}

	/* If common is there, these should be too... */
	isr = virtio_pci_find_capability(pci_dev, VIRTIO_PCI_CAP_ISR_CFG,
					 IORESOURCE_IO | IORESOURCE_MEM,
					 &mdev->modern_bars);
	notify = virtio_pci_find_capability(pci_dev, VIRTIO_PCI_CAP_NOTIFY_CFG,
					    IORESOURCE_IO | IORESOURCE_MEM,
					    &mdev->modern_bars);
	if (!isr || !notify) {
		dev_err(&pci_dev->dev,
			"virtio_pci: missing capabilities %i/%i/%i\n",
			common, isr, notify);
		return -EINVAL;
	}

	err = dma_set_mask_and_coherent(&pci_dev->dev, DMA_BIT_MASK(64));
	if (err)
		err = dma_set_mask_and_coherent(&pci_dev->dev,
						DMA_BIT_MASK(32));
	if (err)
		dev_warn(&pci_dev->dev, "Failed to enable 64-bit or 32-bit DMA.  Trying to continue, but this might not work.\n");

	/* Device capability is only mandatory for devices that have
	 * device-specific configuration.
	 */
	device = virtio_pci_find_capability(pci_dev, VIRTIO_PCI_CAP_DEVICE_CFG,
					    IORESOURCE_IO | IORESOURCE_MEM,
					    &mdev->modern_bars);

	err = pci_request_selected_regions(pci_dev, mdev->modern_bars,
					   "virtio-pci-modern");
	if (err)
		return err;

	err = -EINVAL;
	mdev->common = vp_modern_map_capability(mdev, common,
				      sizeof(struct virtio_pci_common_cfg), 4,
				      0, sizeof(struct virtio_pci_common_cfg),
				      NULL, NULL);
	if (!mdev->common)
		goto err_map_common;
	mdev->isr = vp_modern_map_capability(mdev, isr, sizeof(u8), 1,
					     0, 1,
					     NULL, NULL);
	if (!mdev->isr)
		goto err_map_isr;

	/* Read notify_off_multiplier from config space. */
	pci_read_config_dword(pci_dev,
			      notify + offsetof(struct virtio_pci_notify_cap,
						notify_off_multiplier),
			      &mdev->notify_offset_multiplier);
	/* Read notify length and offset from config space. */
	pci_read_config_dword(pci_dev,
			      notify + offsetof(struct virtio_pci_notify_cap,
						cap.length),
			      &notify_length);

	pci_read_config_dword(pci_dev,
			      notify + offsetof(struct virtio_pci_notify_cap,
						cap.offset),
			      &notify_offset);

	/* We don't know how many VQs we'll map, ahead of the time.
	 * If notify length is small, map it all now.
	 * Otherwise, map each VQ individually later.
	 */
	if ((u64)notify_length + (notify_offset % PAGE_SIZE) <= PAGE_SIZE) {
		mdev->notify_base = vp_modern_map_capability(mdev, notify,
							     2, 2,
							     0, notify_length,
							     &mdev->notify_len,
							     &mdev->notify_pa);
		if (!mdev->notify_base)
			goto err_map_notify;
	} else {
		mdev->notify_map_cap = notify;
	}

	/* Again, we don't know how much we should map, but PAGE_SIZE
	 * is more than enough for all existing devices.
	 */
	if (device) {
		mdev->device = vp_modern_map_capability(mdev, device, 0, 4,
							0, PAGE_SIZE,
							&mdev->device_len,
							NULL);
		if (!mdev->device)
			goto err_map_device;
	}

	return 0;

err_map_device:
	if (mdev->notify_base)
		pci_iounmap(pci_dev, mdev->notify_base);
err_map_notify:
	pci_iounmap(pci_dev, mdev->isr);
err_map_isr:
	pci_iounmap(pci_dev, mdev->common);
err_map_common:
	return err;
}