Intel Extensible Firmware Interface - Manual (Page 494)

Extensible Firmware Interface Specification
12-76 12/01/02 Version 1.10
SrcBarIndex The BAR index in the standard PCI Configuration header to use as
the base address for the memory operation to perform. This allows
all drivers to use BAR relative addressing. The legal range for this
field is 0..5. However, the value
EFI_PCI_IO_PASS_THROUGH_BAR can be used to bypass the
BAR relative addressing and pass Offset to the PCI Root Bridge
I/O Protocol unchanged. Type
EFI_PCI_IO_PASS_THROUGH_BAR is defined in Section 12.4.
SrcOffset The source offset within the BAR specified by SrcBarIndex to
start the memory reads for the copy operation. The caller is
responsible for aligning the
SrcOffset if required.
Count The number of memory operations to perform. Bytes moved is
Width size * Count , starting at DestOffset and
SrcOffset .
Description
The CopyMem() function enables a PCI driver to copy one region of PCI memory space to
another region of PCI memory space on a PCI controller. This is especially useful for video scroll
operations on a memory mapped video buffer.
The memory operations are carried out exactly as requested. The caller is responsible for satisfying
any alignment and memory width restrictions that a PCI controller on a platform might require. For
example on some platforms, width requests of
EfiPciIoWidthUint64 do not work.
If Width is EfiPciWidthUint8 , EfiPciWidthUint16 , EfiPciWidthUint32 , or
EfiPciWidthUint64 , then Count read/write transactions are performed to move the contents
of the SrcOffset buffer to the DestOffset buffer. The implementation must be reentrant,
and it must handle overlapping SrcOffset and DestOffset buffers. This means that the
implementation of CopyMem() must choose the correct direction of the copy operation based on
the type of overlap that exists between the SrcOffset and DestOffset buffers. If either the
SrcOffset buffer or the DestOffset buffer crosses the top of the processor’s address space,
then the result of the copy operation is unpredictable.
The contents of the DestOffset buffer on exit from this service must match the contents of the
SrcOffset buffer on entry to this service. Due to potential overlaps, the contents of the
SrcOffset buffer may be modified by this service. The following rules can be used to guarantee
the correct behavior:
1. If DestOffset > SrcOffset and DestOffset < ( SrcOffset + Width size *
Count ), then the data should be copied from the SrcOffset buffer to the DestOffset
buffer starting from the end of buffers and working toward the beginning of the buffers.
2. Otherwise, the data should be copied from the SrcOffset buffer to the DestOffset buffer
starting from the beginning of the buffers and working toward the end of the buffers.