Intel Extensible Firmware Interface, Specification

Page: 165 / 494

Device I/O Protocol
Version 1.02 12/12/00 147
6.2.5 DEVICE_IO.AllocateBuffer()
Summary
Allocates pages that are suitable for an
EFIBusMasterCommonBuffer
mapping.
Prototype
typedef
EFI_STATUS
(EFIAPI *EFI_IO_ALLOCATE_BUFFER) (
IN EFI_DEVICE_IO_INTERFACE *This,
IN EFI_ALLOCATE_TYPE Type,
IN EFI_MEMORY_TYPE MemoryType,
IN UINTN Pages,
IN OUT EFI_PHYSICAL_ADDRESS
*HostAddress
);
Parameters
This
A pointer to the
EFI_DEVICE_IO_INTERFACE
. Type
EFI_DEVICE_IO_INTERFACE
is defined in Section 6.2.
Type
The type allocation to perform. Type
EFI_ALLOCATE_TYPE
is
defined in Chapter 3.
MemoryType
The type of memory to allocate,
EfiBootServicesData
or
EfiRuntimeServicesData
. Type
EFI_MEMORY_TYPE
is defined
in Chapter 3.
Pages
The number of pages to allocate.
HostAddress
A pointer to store the base address of the allocated range. Type
EFI_
PHYSICAL_ADDRESS
is defined in Chapter 3.
Description
The
AllocateBuffer()
function allocates pages that are suitable for an
EFIBusMasterCommonBuffer
mapping.
The
AllocateBuffer()
function internally calls
AllocatePages()
to allocate a memory
range that can be mapped as an
EFIBusMasterCommonBuffer
. When the buffer is no longer
needed, the driver frees the memory with a call to
FreeBuffer()
.
Allocation requests of
Type AllocateAnyPages
will allocate any available range of pages that
satisfies the request. On input the data pointed to by
HostAddress
is ignored.