WIP: USB

system/devices/device-abi.zig

@@ -56,6 +56,10 @@ pub const maximum_device_resources = 8;
 /// `DeviceDescriptor.parent` for a device with no parent — a root of the device tree.
 pub const no_parent: u64 = ~@as(u64, 0);
 
+/// `DeviceDescriptor.pci_class` for a device that is not a PCI function. (Zero would be
+/// ambiguous: 0x000000 is a real class code, "unclassified device".)
+pub const no_pci_class: u64 = ~@as(u64, 0);
+
 /// A device, as snapshotted for user space by `device_enumerate`. A driver scans
 /// these to find the hardware it owns, claims it, and maps its MMIO.
 ///
@@ -69,6 +73,11 @@ pub const DeviceDescriptor = extern struct {
     id: u64,
     parent: u64, // a device id, or `no_parent`
     class: u64, // a DeviceClass value
+    // The PCI class/subclass/prog-IF triple packed as 0xCCSSPP when this device is a PCI
+    // function, or `no_pci_class` otherwise. This is how a manager tells *what* a
+    // `pci_device` is (an xHCI controller, an AHCI controller) — decode the triple into
+    // names with the pci-class module.
+    pci_class: u64,
     hid_len: u64,
     resource_count: u64,
     hid: [8]u8,