[ehci] Allow UHCI/OHCI controllers to locate the EHCI companion controller

Signed-off-by: Michael Brown <mcb30@ipxe.org>

src/drivers/usb/ehci.c

 	}
 }
 
+/**
+ * Locate EHCI companion controller
+ *
+ * @v pci		PCI device
+ * @ret busdevfn	EHCI companion controller bus:dev.fn (if any)
+ */
+unsigned int ehci_companion ( struct pci_device *pci ) {
+	struct pci_device tmp;
+	unsigned int busdevfn;
+	int rc;
+
+	/* Look for an EHCI function on the same PCI device */
+	busdevfn = pci->busdevfn;
+	while ( ++busdevfn <= PCI_LAST_FUNC ( pci->busdevfn ) ) {
+		pci_init ( &tmp, busdevfn );
+		if ( ( rc = pci_read_config ( &tmp ) ) != 0 )
+			continue;
+		if ( tmp.class == PCI_CLASS ( PCI_CLASS_SERIAL,
+					      PCI_CLASS_SERIAL_USB,
+					      PCI_CLASS_SERIAL_USB_EHCI ) )
+			return busdevfn;
+	}
+
+	return 0;
+}
+
 /******************************************************************************
  *
  * Run / stop / reset

src/drivers/usb/ehci.h

 	struct ehci_ring ring;
 };
 
+extern unsigned int ehci_companion ( struct pci_device *pci );
+
 #endif /* _IPXE_EHCI_H */

src/include/ipxe/pci.h

 #define PCI_BUSDEVFN( bus, slot, func )	\
 	( ( (bus) << 8 ) | ( (slot) << 3 ) | ( (func) << 0 ) )
 #define PCI_FIRST_FUNC( busdevfn )	( (busdevfn) & ~0x07 )
+#define PCI_LAST_FUNC( busdevfn )	( (busdevfn) | 0x07 )
 
 #define PCI_BASE_CLASS( class )		( (class) >> 16 )
 #define PCI_SUB_CLASS( class )		( ( (class) >> 8 ) & 0xff )