Intel Extensible Firmware Interface - Manual (Page 955)

32/64-Bit UNDI Specification
Version 1.10 12/01/02 E-89
E.4.19 Receive
When the network adapter has received a frame, this command is used to copy the frame into
driver/application storage. Once a frame has been copied, it is removed from the receive queue.
E.4.19.1 Issuing the Command
To issue a Receive command, create a CDB and fill it in as shown in the table below:
CDB Field How to initialize the CDB structure for a Receive command
OpCode PXE_OPCODE_RECEIVE
OpFlags Set as needed.
CPBsize sizeof(PXE_CPB_RECEIVE)
DBsize sizeof(PXE_DB_RECEIVE)
CPBaddr Address of a PXE_CPB_RECEIVE structure.
DBaddr Address of a PXE_DB_RECEIVE structure.
StatCode PXE_STATCODE_INITIALIZE
StatFlags PXE_STATFLAGS_INITIALIZE
IFnum A valid interface number from zero to !PXE.IFcnt .
Control Set as needed.
Preparing the CPB
If multiple frames per command are supported (see !PXE.Implementation flags), multiple
CPBs can be packed together. For each complete received frame, a receive buffer large enough to
contain the entire unfragmented frame needs to be described in the CPB. Note that if a smaller than
required buffer is provided, only a portion of the packet is received into the buffer, and the
remainder of the packet is lost. Subsequent attempts to receive the same packet with a corrected
(larger) buffer will be unsuccessful, because the packet will have been flushed from the queue.
#pragma pack(1)
typedef struct s_pxe_cpb_receive {
// Address of first byte of receive buffer. This is also the
// first byte of the frame header. This address must be a
// processor-based address for S/W UNDI and a device-based
// address for H/W UNDI.
PXE_UINT64 BufferAddr;
// Length of receive buffer. This must be large enough to hold
// the received frame (media header + data). If the length of
// smaller than the received frame, data will be lost.
PXE_UINT32 BufferLen;
// Reserved, must be set to zero.
PXE_UINT32 reserved;
} PXE_CPB_RECEIVE;
#pragma pack()