EmbeddedPkg: introduce EDKII Platform Has ACPI GUID

The presence of this GUID in the PPI database, and/or in the DXE protocol
database (as dictated by the platform's needs in these firmware phases)
implies that the platform provides the operating system with an ACPI-based
hardware description. This is not necessarily exclusive with other types
of hardware description (for example, a Device Tree-based one).

A platform PEIM and/or DXE driver is supposed to produce a single instance
of the PPI and/or protocol (with NULL contents), if appropriate. The
decision to produce the PPI and/or protocol is platform specific; for
example, in the DXE phase, it could depend on an HII checkbox / underlying
non-volatile UEFI variable.

In the DXE phase, the protocol is meant to be depended-upon by
"MdeModulePkg/Universal/Acpi/AcpiTableDxe", indirectly:

* In the long term, interested platforms will establish this dependency by
  hooking an (upcoming) NULL-class DepexLib instance into AcpiTableDxe in
  their DSC files, pointing DepexLib's DEPEX through a FixedAtBuild PCD to
  the GUID introduced here. (For the prerequisite BaseTools feature, refer
  to <https://bugzilla.tianocore.org/show_bug.cgi?id=443>).

* In the short term, an interested platform may hook a private NULL-class
  library instance (called e.g. "PlatformHasAcpiLib") into AcpiTableDxe.
  Such a library instance would be a specialization of the above described
  generic DepexLib, with the DEPEX open-coded on the GUID introduced here.

Either way, the platform makes EFI_ACPI_TABLE_PROTOCOL and (if enabled)
EFI_ACPI_SDT_PROTOCOL dependent on the platform's dynamic decision to
produce or not to produce a NULL protocol instance with this GUID.

In turn, other (platform and universal) DXE drivers that produce ACPI
tables will wait for EFI_ACPI_TABLE_PROTOCOL / EFI_ACPI_SDT_PROTOCOL, via
DEPEX, protocol notify, or a simple gBS->LocateProtocol() in a "late
enough" callback (such as Ready To Boot).

Because this GUID is not standard, it is prefixed with EDKII / Edkii, as
seen elsewhere in MdeModulePkg and SecurityPkg. In addition, an effort is
made to avoid the phrase "AcpiPlatform", as that belongs to drivers /
libraries that produce platform specific ACPI content (as opposed to
deciding whether the entire firmware will have access to
EFI_ACPI_TABLE_PROTOCOL, or any similar facilities in the PEI phase).

Cc: Ard Biesheuvel <ard.biesheuvel@linaro.org>
Cc: Leif Lindholm <leif.lindholm@linaro.org>
Contributed-under: TianoCore Contribution Agreement 1.0
Signed-off-by: Laszlo Ersek <lersek@redhat.com>
Reviewed-by: Ard Biesheuvel <ard.biesheuvel@linaro.org>

1 files changed, 35 insertions, 0 deletions

diff --git a/EmbeddedPkg/Include/Guid/PlatformHasAcpi.h b/EmbeddedPkg/Include/Guid/PlatformHasAcpi.h
new file mode 100644
index 0000000000..ad51782137
--- /dev/null
+++ b/EmbeddedPkg/Include/Guid/PlatformHasAcpi.h
@@ -0,0 +1,35 @@
+/** @file

+  EDKII Platform Has ACPI GUID

+

+  A NULL protocol instance with this GUID in the DXE protocol database, and/or

+  a NULL PPI with this GUID in the PPI database, implies that the platform

+  provides the operating system with an ACPI-based hardware description. Note

+  that this is not necessarily exclusive with different kinds of hardware

+  description (for example, a Device Tree-based one). A platform driver and/or

+  PEIM is supposed to produce a single instance of the protocol and/or PPI

+  (with NULL contents), if appropriate.

+

+  Copyright (C) 2017, Red Hat, Inc.

+

+  This program and the accompanying materials are licensed and made available

+  under the terms and conditions of the BSD License that accompanies this

+  distribution. The full text of the license may be found at

+  http://opensource.org/licenses/bsd-license.php.

+

+  THE PROGRAM IS DISTRIBUTED UNDER THE BSD LICENSE ON AN "AS IS" BASIS, WITHOUT

+  WARRANTIES OR REPRESENTATIONS OF ANY KIND, EITHER EXPRESS OR IMPLIED.

+**/

+

+

+#ifndef __EDKII_PLATFORM_HAS_ACPI_H__

+#define __EDKII_PLATFORM_HAS_ACPI_H__

+

+#define EDKII_PLATFORM_HAS_ACPI_GUID \

+  { \

+    0xf0966b41, 0xc23f, 0x41b9, \

+    { 0x96, 0x04, 0x0f, 0xf7, 0xe1, 0x11, 0x96, 0x5a } \

+  }

+

+extern EFI_GUID gEdkiiPlatformHasAcpiGuid;

+

+#endif