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Decode PCI class codes in device discovery

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`pci_device` alone says nothing — an ISA bridge, an AHCI controller, and an xHCI USB
controller are all just `pci_device` by DeviceClass. The identity lives in the 24-bit
class code (base class / subclass / prog-IF) that discovery already recorded in
ids.pci_class but the dump threw away.

New system/devices/pci-class.zig (module `pci-class`): pure reference data from the PCI
spec (per the OSDev PCI table) decoding the triple into names — className, subclassName,
progIfName, plus ClassCode.unpack. No hardware access, so it's shared by kernel
discovery and any future user-space PCI tool. device_tree.dump now prints, under each
PCI function, its class/subclass/prog-IF as both hex and name:

    pci0:00:1f.0 [pci_device]
      class 0x06 (Bridge)  subclass 0x01 (ISA Bridge)  progif 0x00
    pci0:00:1f.2 [pci_device]
      class 0x01 (Mass Storage Controller)  subclass 0x06 (Serial ATA Controller)  progif 0x01 (AHCI 1.0)

Host test covers the decoder (bridge/AHCI/xHCI, the "Other" 0x80 convention, unknowns).
Suite 41/41 plus host tests.
This commit is contained in:
Daniel Samson
2026-07-10 21:35:20 +01:00
parent 3ec2d1828a
commit d702d2e9ae
3 changed files with 284 additions and 0 deletions
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system/devices/device-model.zig
+16
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@@ -13,6 +13,7 @@
const std = @import("std");
const device_abi = @import("device-abi");
const pci_class = @import("pci-class");
/// The hardware primitives a discovery backend needs but can't express portably.
/// The kernel injects an implementation (the architecture VMM + port I/O), so the device
@@ -195,6 +196,21 @@ fn dumpNode(device: *const Device, depth: usize, emit: *const fn ([]const u8) vo
std.fmt.bufPrint(buffer[indent..], "{s} [{s}]\n", .{ device.name(), @tagName(device.class) }) catch return;
emit(buffer[0 .. indent + body.len]);
// For a PCI function, decode its class code — the (class / subclass / prog-IF)
// triple that says what it actually is, which the coarse `DeviceClass` can't.
if (device.ids.pci_class) |packed_code| {
const cc = pci_class.ClassCode.unpack(packed_code);
var cbuf: [200]u8 = undefined;
const pad = @min(indent + 2, 42);
@memset(cbuf[0..pad], ' ');
const pif = pci_class.progIfName(cc.base, cc.subclass, cc.prog_if);
const cline = if (pif.len != 0)
std.fmt.bufPrint(cbuf[pad..], "class 0x{x:0>2} ({s}) subclass 0x{x:0>2} ({s}) progif 0x{x:0>2} ({s})\n", .{ cc.base, pci_class.className(cc.base), cc.subclass, pci_class.subclassName(cc.base, cc.subclass), cc.prog_if, pif }) catch return
else
std.fmt.bufPrint(cbuf[pad..], "class 0x{x:0>2} ({s}) subclass 0x{x:0>2} ({s}) progif 0x{x:0>2}\n", .{ cc.base, pci_class.className(cc.base), cc.subclass, pci_class.subclassName(cc.base, cc.subclass), cc.prog_if }) catch return;
emit(cbuf[0 .. pad + cline.len]);
}
for (device.resources[0..device.resource_count]) |r| {
var rbuf: [200]u8 = undefined;
const pad = @min(indent + 2, 42);