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a536e5d699
Replace traditional `#ifndef`/`#define`/`#endif` include guards with
`#pragma` once.
`#pragma once` is a widely supported preprocessor directive that
prevents header files from being included multiple times. It is
supported by all toolchains used to build edk2: GCC, Clang/LLVM, and
MSVC.
Note: Headers taken directly from external projects, such as those
in OvmfPkg/Include/IndustryStandard/Xen/ were not modified since they
may be periodically re-synced and do not follow other edk2 coding
stadards.
Compared to macro-based include guards, `#pragma once`:
- Eliminates the risk of macro name collisions or copy/paste errors
where two headers inadvertently use the same guard macro.
- Eliminate inconsistency in the way include guard macros are named
(e.g., some files use `__FILE_H__`, others use `FILE_H_`, etc.).
- Reduces boilerplate (three lines replaced by one).
- Avoids polluting the macro namespace with guard symbols.
- Can improve build times as the preprocessor can skip re-opening the
file entirely, rather than re-reading it to find the matching
`#endif` ("multiple-include optimization").
- Note that some compilers may already optimize traditional include
guards, by recognzining the idiomatic pattern.
This change is made acknowledging that overall portability of the
code will technically be reduced, as `#pragma once` is not part of the
C/C++ standards.
However, this is considered acceptable given:
1. edk2 already defines a subset of supported compilers in
BaseTools/Conf/tools_def.template, all of which have supported
`#pragma once` for over two decades.
2. There have been concerns raised to the project about inconsistent
include guard naming and potential macro collisions.
Approximate compiler support dates:
- MSVC: Supported since Visual C++ 4.2 (1996)
- GCC: Supported since 3.4 (2004)
(http://gnu.ist.utl.pt/software/gcc/gcc-3.4/changes.html)
- Clang (LLVM based): Since initial release in 2007
Signed-off-by: Michael Kubacki <michael.kubacki@microsoft.com>
51 lines
1.5 KiB
C
51 lines
1.5 KiB
C
/** @file
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Macro and type definitions for QEMU's Red Hat vendor-specific PCI
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capabilities that provide various hints about PCI Bridges.
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Refer to "docs/pcie_pci_bridge.txt" in the QEMU source directory.
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Copyright (C) 2017, Red Hat, Inc.
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SPDX-License-Identifier: BSD-2-Clause-Patent
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**/
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#pragma once
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#include <IndustryStandard/Pci23.h>
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//
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// The hints apply to PCI Bridges whose PCI_DEVICE_INDEPENDENT_REGION.VendorId
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// equals the following value.
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//
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#define QEMU_PCI_BRIDGE_VENDOR_ID_REDHAT 0x1B36
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//
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// Common capability header for all hints.
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//
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#pragma pack (1)
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typedef struct {
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EFI_PCI_CAPABILITY_VENDOR_HDR VendorHdr;
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UINT8 Type;
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} QEMU_PCI_BRIDGE_CAPABILITY_HDR;
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#pragma pack ()
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//
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// Values defined for QEMU_PCI_BRIDGE_CAPABILITY_HDR.Type.
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//
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#define QEMU_PCI_BRIDGE_CAPABILITY_TYPE_RESOURCE_RESERVATION 0x01
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//
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// PCI Resource Reservation structure for when
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// QEMU_PCI_BRIDGE_CAPABILITY_HDR.Type equals
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// QEMU_PCI_BRIDGE_CAPABILITY_TYPE_RESOURCE_RESERVATION.
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//
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#pragma pack (1)
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typedef struct {
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QEMU_PCI_BRIDGE_CAPABILITY_HDR BridgeHdr;
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UINT32 BusNumbers;
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UINT64 Io;
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UINT32 NonPrefetchable32BitMmio;
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UINT32 Prefetchable32BitMmio;
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UINT64 Prefetchable64BitMmio;
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} QEMU_PCI_BRIDGE_CAPABILITY_RESOURCE_RESERVATION;
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#pragma pack ()
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