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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>
71 lines
2.5 KiB
C
71 lines
2.5 KiB
C
/** @file
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Library class layered on top of PciCapLib that allows clients to plug a
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PciSegmentLib backend into PciCapLib, for config space access.
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Copyright (C) 2018, 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 <Library/PciCapLib.h>
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/**
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Create a PCI_CAP_DEV object from the PCI Segment:Bus:Device.Function
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quadruplet. The config space accessors are based upon PciSegmentLib.
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@param[in] MaxDomain If MaxDomain is PciCapExtended, then
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PciDevice->ReadConfig() and PciDevice->WriteConfig()
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will delegate extended config space accesses too to
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PciSegmentReadBuffer() and PciSegmentWriteBuffer(),
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respectively. Otherwise, PciDevice->ReadConfig() and
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PciDevice->WriteConfig() will reject accesses to
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extended config space with RETURN_UNSUPPORTED, without
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calling PciSegmentReadBuffer() or
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PciSegmentWriteBuffer(). By setting MaxDomain to
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PciCapNormal, the platform can prevent undefined
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PciSegmentLib behavior when the PCI root bridge under
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the PCI device at Segment:Bus:Device.Function doesn't
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support extended config space.
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@param[in] Segment 16-bit wide segment number.
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@param[in] Bus 8-bit wide bus number.
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@param[in] Device 5-bit wide device number.
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@param[in] Function 3-bit wide function number.
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@param[out] PciDevice The PCI_CAP_DEV object constructed as described above.
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PciDevice can be passed to the PciCapLib APIs.
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@retval RETURN_SUCCESS PciDevice has been constructed and output.
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@retval RETURN_INVALID_PARAMETER Device or Function does not fit in the
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permitted number of bits.
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@retval RETURN_OUT_OF_RESOURCES Memory allocation failed.
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**/
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RETURN_STATUS
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EFIAPI
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PciCapPciSegmentDeviceInit (
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IN PCI_CAP_DOMAIN MaxDomain,
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IN UINT16 Segment,
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IN UINT8 Bus,
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IN UINT8 Device,
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IN UINT8 Function,
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OUT PCI_CAP_DEV **PciDevice
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);
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/**
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Free the resources used by PciDevice.
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@param[in] PciDevice The PCI_CAP_DEV object to free, originally produced by
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PciCapPciSegmentDeviceInit().
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**/
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VOID
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EFIAPI
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PciCapPciSegmentDeviceUninit (
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IN PCI_CAP_DEV *PciDevice
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);
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