[SPDK] Can I use spdk_pci_hook_device to implement a virtual NVMe device?

[oscar.huang at microchip.com]

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I'd like to create a virtual NVMe device and use SPDK NVMe APIs to operate it. It looks like spdk_pci_hook_device() can add a virtual PCI device to SPDK PCI system:

void spdk_pci_hook_device(struct spdk_pci_driver *drv, struct spdk_pci_device *dev);

But the struct spdk_pci_device only contains the following callbacks:
    int (*map_bar)(struct spdk_pci_device *dev, uint32_t bar, 
               void **mapped_addr, uint64_t *phys_addr, uint64_t *size);
    int (*unmap_bar)(struct spdk_pci_device *dev, uint32_t bar, 
             void *addr);
    int (*cfg_read)(struct spdk_pci_device *dev, void *value,
            uint32_t len, uint32_t offset);
    int (*cfg_write)(struct spdk_pci_device *dev, void *value,
             uint32_t len, uint32_t offset);
    void (*detach)(struct spdk_pci_device *dev);

It does not have mmio callbacks. When applications write a device memory, sometimes it needs to trigger some actions on the device. Without mmio callbacks, how to make a useful virtual device with spdk_pci_hook_device? Pls suggest. Much appreciated!