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Preventing Alignment Faults VOID ScsiDeviceNodeInit ( IN OUT SCSI_DEVICE_PATH *ScsiDeviceNode, IN UINT16 Pun, IN UINT16 Lun ) { ScsiDeviceNode = MESSAGING_DEVICE_PATH。 ScsiDeviceNode = MSG_SCSI_DP。 SetDevicePathNodeLength (amp。 ScsiDeviceNode, sizeof(SCSI_DEVICE_PATH))。 ScsiDeviceNode = Pun。 ScsiDeviceNode = Lun。 } BAD ScsiDeviceNode may not be aligned Driver Guidelines Preventing Alignment Faults VOID ScsiDeviceNodeInit ( IN OUT SCSI_DEVICE_PATH *ScsiDeviceNode, IN UINT16 Pun, IN UINT16 Lun ) { SCSI_DEVICE_PATH MyDeviceNode。 = MESSAGING_DEVICE_PATH。 = MSG_SCSI_DP。 SetDevicePathNodeLength (amp。 , sizeof(SCSI_DEVICE_PATH))。 = Pun。 = Lun。 gBSCopyMem (ScsiDeviceNode, amp。 MyDeviceNode, sizeof(SCSI_DEVICE_PATH))。 } GOOD gBSCopyMem() handles all alignments MyDeviceNode is aligned Driver Guidelines Use EFI Driver Library Functions CHILD_DEVICE Child。 Child = EfiLibAllocateZeroPool (sizeof (CHILD_DEVICE))。 if (Child == NULL) { return EFI_OUT_OF_RESOURCES。 } Library Functions Simplify Source Code Library Functions May Reduce Size CHILD_DEVICE Child。 Status = gBSAllocatePool ( EfiBootServicesData, sizeof (CHILD_DEVICE), amp。 Child )。 if (EFI_ERROR (Status)) { return Status。 } gBSSetMem (Child, sizeof (CHILD_DEVICE), 0)。 OK GOOD Driver Guidelines EFI Device Paths  () ChildDevicePath = EfiAppendDevicePathNode ( ControllerDevicePath, ChildDevicePathNode )。 if (ChildDevicePath == NULL) { return(EFI_OUT_OF_RESOURCES)。 } gBSFreePool (ChildDevicePath)。  () Parent Device Path is Opaque Not Parsed by Bus Drivers Driver Guidelines Bus Walk Tips  Use LocateHandleBuffer(Bus I/O Protocol)  Do not scan PCI configuration space  Implement support for RemainingDevicePath  Highly remended for all bus drivers  (. SCSI, Fibre Channel, etc.)  Allows bus driver to bypass full enumeration.  Reduces boot time Driver Guidelines Component Name Protocol  Limit Lengths of Names to 40 Unicode Characters  Include Driver Name and Version Number  UNDI Driver (Network Interface Controller)  Typically the Name of the PCI Controller  MAC Node Produced by an UNDI Driver  Identify Location of Physical Connector on NIC  PCI Slots  Identify Physical Location of PCI Slots in the System  SCSI / SCSI RAID / Fiber Channel  Controller Typically name of the PCI Controller  Channel Identify Physical Location of the SCSI Channel  Disk Use Results from INQUIRY Command Driver Guidelines Option ROM Size Reduction  Use EFI Compression  Compile with EFI Byte Code Compiler  Single Binary for x86, x64 and Itanium  Smaller than Itanium Binaries  Comparable to x86 Binaries  Compresses Well ~ 50% Driver Guidelines How To Improve Portability  Do Not Assume Max Number of Children  Do Not Use Fixed Memory Addresses  Do Not Use Assembly  Do Not Use Floating Point Arithmetic  Some Minor EBC Porting Considerations  Bus Drivers Should Support Producing 1 Child at a time if possible (improves boot performance) D。