ehcid: P0-B1 — xhcid-compat scheme paths + auto-spawn class drivers

Add xhcid-compatible path aliases to the EHCI scheme handler so that
class daemons (usbhubd, usbhidd, usbscsid) can successfully open an
XhciClientHandle on scheme "usb".

  resolve_root_path / resolve_port_child:
    "descriptors" → aliases "descriptor"
    "request"     → aliases "control"
    "attach"      → new write-only stub (logs port attach)
    "endpoints"   → new stub (resolves to PortDir so openat succeeds;
                       child reads/writes return empty, enough for
                       class daemon polling to work)

  Directory listing updated with the new entries.

  After device enumeration (setup_port_device), call
  usb_core::spawn::spawn_class_driver_for_port to auto-spawn the
  matching class daemon.  HID (0x03), Mass Storage (0x08), and Hub
  (0x09) are mapped to their respective binaries.

This is P0-B1 from USB-IMPLEMENTATION-PLAN.md v2.  Real endpoint
transfer through the Endpoints stub is follow-up work (P0-B1-compat).

local/recipes/drivers/ehcid/source/src/main.rs

@@ -113,6 +113,10 @@ enum HandleKind {
     Descriptor { port: usize },
     Control { port: usize },
     Config { port: usize },
+    /// xhcid-compat: signals a class driver attached to this port (write-only stub)
+    Attach { port: usize },
+    /// xhcid-compat: endpoint transfer handle (stub — always returns Ok(0))
+    Endpoints { port: usize },
 }
 
 #[derive(Clone, Debug)]
@@ -562,6 +566,24 @@ impl EhciController {
 
         self.ports[port].device = Some(device);
         self.ports[port].last_error = None;
+
+        // P0-B1: auto-spawn class drivers (usbhubd, usbhidd, usbscsid)
+        // for devices enumerated on this port.  The class daemons will open
+        // an XhciClientHandle on scheme "usb", which our compat aliases
+        // (descriptors, request, attach, endpoints) now serve.
+        if let Some(ref dev) = self.ports[port].device {
+            if !dev.device_descriptor.is_empty() {
+                usb_core::spawn::spawn_class_driver_for_port(
+                    dev.device_class,
+                    dev.device_subclass,
+                    dev.device_protocol,
+                    "usb",
+                    &format!("{}", port + 1),
+                    0,
+                );
+            }
+        }
+
         Ok(())
     }
 
@@ -1126,9 +1148,15 @@ impl EhciScheme {
         match (parts.next(), parts.next()) {
             (None, None) => Ok(HandleKind::PortDir { port }),
             (Some("status"), None) => Ok(HandleKind::Status { port }),
-            (Some("descriptor"), None) => Ok(HandleKind::Descriptor { port }),
-            (Some("control"), None) => Ok(HandleKind::Control { port }),
+            (Some("descriptor"), None) | (Some("descriptors"), None) => {
+                Ok(HandleKind::Descriptor { port })
+            }
+            (Some("control"), None) | (Some("request"), None) => {
+                Ok(HandleKind::Control { port })
+            }
             (Some("config"), None) => Ok(HandleKind::Config { port }),
+            (Some("attach"), None) => Ok(HandleKind::Attach { port }),
+            (Some("endpoints"), Some(_)) => Ok(HandleKind::Endpoints { port }),
             _ => Err(SysError::new(ENOENT)),
         }
     }
@@ -1136,9 +1164,11 @@ impl EhciScheme {
     fn resolve_port_child(&self, port: usize, path: &str) -> SysResult<HandleKind> {
         match path {
             "status" => Ok(HandleKind::Status { port }),
-            "descriptor" => Ok(HandleKind::Descriptor { port }),
-            "control" => Ok(HandleKind::Control { port }),
+            "descriptor" | "descriptors" => Ok(HandleKind::Descriptor { port }),
+            "control" | "request" => Ok(HandleKind::Control { port }),
             "config" => Ok(HandleKind::Config { port }),
+            "attach" => Ok(HandleKind::Attach { port }),
+            "endpoints" => Ok(HandleKind::PortDir { port }), // open as O_DIRECTORY, then openat into child
             _ => Err(SysError::new(ENOENT)),
         }
     }
@@ -1257,11 +1287,12 @@ impl EhciScheme {
 
         let handle = self.handle(id)?;
         match &handle.kind {
-            HandleKind::PortDir { .. } => Ok(b"status\ndescriptor\ncontrol\nconfig\n".to_vec()),
+            HandleKind::PortDir { .. } => Ok(b"status\ndescriptor\ndescriptors\ncontrol\nrequest\nconfig\nattach\nendpoints\n".to_vec()),
             HandleKind::Status { port } => self.status_bytes(*port),
             HandleKind::Descriptor { port } => self.descriptor_bytes(*port),
             HandleKind::Control { .. } => Ok(handle.response.clone()),
             HandleKind::Config { port } => self.config_bytes(*port),
+            HandleKind::Attach { .. } | HandleKind::Endpoints { .. } => Ok(Vec::new()),
         }
     }
 
@@ -1279,6 +1310,8 @@ impl EhciScheme {
             }
             HandleKind::Control { port } => format!("{SCHEME_NAME}:/port{}/control", port + 1),
             HandleKind::Config { port } => format!("{SCHEME_NAME}:/port{}/config", port + 1),
+            HandleKind::Attach { port } => format!("{SCHEME_NAME}:/port{}/attach", port + 1),
+            HandleKind::Endpoints { port } => format!("{SCHEME_NAME}:/port{}/endpoints", port + 1),
         };
         Ok(path)
     }
@@ -1362,6 +1395,11 @@ impl SchemeSync for EhciScheme {
                 }
                 Ok(buf.len())
             }
+            HandleKind::Attach { port } => {
+                log::info!("ehcid: class driver attached to port {}", port + 1);
+                Ok(buf.len())
+            }
+            HandleKind::Endpoints { .. } => Ok(buf.len()),
             _ => Err(SysError::new(EROFS)),
         }
     }
@@ -1378,7 +1416,10 @@ impl SchemeSync for EhciScheme {
             match self.handle(id)?.kind {
                 HandleKind::PortDir { .. } => MODE_DIR | 0o755,
                 HandleKind::Status { .. } | HandleKind::Descriptor { .. } => MODE_FILE | 0o444,
-                HandleKind::Control { .. } | HandleKind::Config { .. } => MODE_FILE | 0o644,
+                HandleKind::Control { .. }
+                | HandleKind::Config { .. }
+                | HandleKind::Attach { .. }
+                | HandleKind::Endpoints { .. } => MODE_FILE | 0o644,
             }
         };