//! PCI transport for VirtIO.

pub mod bus;

use super::DeviceType;

/// The PCI vendor ID for VirtIO devices.
const VIRTIO_VENDOR_ID: u16 = 0x1af4;

/// The offset to add to a VirtIO device ID to get the corresponding PCI device ID.
const PCI_DEVICE_ID_OFFSET: u16 = 0x1040;

const TRANSITIONAL_NETWORK: u16 = 0x1000;
const TRANSITIONAL_BLOCK: u16 = 0x1001;
const TRANSITIONAL_MEMORY_BALLOONING: u16 = 0x1002;
const TRANSITIONAL_CONSOLE: u16 = 0x1003;
const TRANSITIONAL_SCSI_HOST: u16 = 0x1004;
const TRANSITIONAL_ENTROPY_SOURCE: u16 = 0x1005;
const TRANSITIONAL_9P_TRANSPORT: u16 = 0x1009;

fn device_type(pci_device_id: u16) -> DeviceType {
    match pci_device_id {
        TRANSITIONAL_NETWORK => DeviceType::Network,
        TRANSITIONAL_BLOCK => DeviceType::Block,
        TRANSITIONAL_MEMORY_BALLOONING => DeviceType::MemoryBalloon,
        TRANSITIONAL_CONSOLE => DeviceType::Console,
        TRANSITIONAL_SCSI_HOST => DeviceType::ScsiHost,
        TRANSITIONAL_ENTROPY_SOURCE => DeviceType::EntropySource,
        TRANSITIONAL_9P_TRANSPORT => DeviceType::_9P,
        id if id >= PCI_DEVICE_ID_OFFSET => DeviceType::from(id - PCI_DEVICE_ID_OFFSET),
        _ => DeviceType::Invalid,
    }
}

#[cfg(test)]
mod tests {
    use super::*;

    #[test]
    fn transitional_device_ids() {
        assert_eq!(device_type(0x1000), DeviceType::Network);
        assert_eq!(device_type(0x1002), DeviceType::MemoryBalloon);
        assert_eq!(device_type(0x1009), DeviceType::_9P);
    }

    #[test]
    fn offset_device_ids() {
        assert_eq!(device_type(0x1045), DeviceType::MemoryBalloon);
        assert_eq!(device_type(0x1049), DeviceType::_9P);
        assert_eq!(device_type(0x1058), DeviceType::Memory);
        assert_eq!(device_type(0x1040), DeviceType::Invalid);
        assert_eq!(device_type(0x1059), DeviceType::Invalid);
    }
}