Intel Extensible Firmware Interface Specification page 405

G.3.1.3 PXE_BUSTYPE
Used to convert a 4-character ASCII identifier to a 32-bit unsigned integer.
#if PXE_INTEL_ORDER
# define PXE_BUSTYPE(a,b,c,d)
((((PXE_UINT32)(d) & 0xFF) << 24) |
(((PXE_UINT32)(c) & 0xFF) << 16) |
(((PXE_UINT32)(b) & 0xFF) << 8) |
((PXE_UINT32)(a) & 0xFF))
#else
# define PXE_BUSTYPE(a,b,c,d)
((((PXE_UINT32)(a) & 0xFF) << 24) |
(((PXE_UINT32)(b) & 0xFF) << 16) |
(((PXE_UINT32)(c) & 0xFF) << 8) |
((PXE_UINT32)(f) & 0xFF))
#endif
//*******************************************************
// UNDI ROM ID and devive ID signature
//*******************************************************
#define PXE_BUSTYPE_PXE
//*******************************************************
// BUS ROM ID signatures
//*******************************************************
#define PXE_BUSTYPE_PCI
#define PXE_BUSTYPE_PC_CARD
#define PXE_BUSTYPE_USB
#define PXE_BUSTYPE_1394
Version 1.02
32/64-bit UNDI Specification
\
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\
\
\
\
\
PXE_BUSTYPE('!', 'P', 'X', 'E')
PXE_BUSTYPE('P', 'C', 'I', 'R')
PXE_BUSTYPE('P', 'C', 'C', 'R')
PXE_BUSTYPE('U', 'S', 'B', 'R')
PXE_BUSTYPE('1', '3', '9', '4')
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