Re: [PATCH v3 04/12] MdeModulePkg: introduce EDKII Platform Has ACPI GUID

[Ard Biesheuvel <ard.biesheuvel@linaro.org>]

On 24 March 2017 at 22:38, Laszlo Ersek <lersek@redhat.com> wrote:
> 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=444>).
>
> * 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: Feng Tian <feng.tian@intel.com>
> Cc: Leif Lindholm <leif.lindholm@linaro.org>
> Cc: Star Zeng <star.zeng@intel.com>
> Contributed-under: TianoCore Contribution Agreement 1.0
> Signed-off-by: Laszlo Ersek <lersek@redhat.com>

Reviewed-by: Ard Biesheuvel <ard.biesheuvel@linaro.org>

> ---
>
> Notes:
>     v3:
>     - rename gEdkiiPlatformHasAcpiProtocolGuid to gEdkiiPlatformHasAcpiGuid
>       [Star]
>     - update commit message and code comments to reflect possible use as a
>       PPI as well [Star]
>     - move GUID from ArmPkg to MdeModulePkg [Leif, Ard]
>     - split PlatformHasAcpiLib to a separate patch [Star]
>
>  MdeModulePkg/MdeModulePkg.dec               |  3 ++
>  MdeModulePkg/Include/Guid/PlatformHasAcpi.h | 35 ++++++++++++++++++++
>  2 files changed, 38 insertions(+)
>
> diff --git a/MdeModulePkg/MdeModulePkg.dec b/MdeModulePkg/MdeModulePkg.dec
> index 626e479f5e45..2d94881206d3 100644
> --- a/MdeModulePkg/MdeModulePkg.dec
> +++ b/MdeModulePkg/MdeModulePkg.dec
> @@ -382,6 +382,9 @@ [Guids]
>    gEdkiiNonDiscoverableUhciDeviceGuid = { 0xA8CDA0A2, 0x4F37, 0x4A1B, {0x8E, 0x10, 0x8E, 0xF3, 0xCC, 0x3B, 0xF3, 0xA8 } }
>    gEdkiiNonDiscoverableXhciDeviceGuid = { 0xB1BE0BC5, 0x6C28, 0x442D, {0xAA, 0x37, 0x15, 0x1B, 0x42, 0x57, 0xBD, 0x78 } }
>
> +  ## Include/Guid/PlatformHasAcpi.h
> +  gEdkiiPlatformHasAcpiGuid = { 0xf0966b41, 0xc23f, 0x41b9, { 0x96, 0x04, 0x0f, 0xf7, 0xe1, 0x11, 0x96, 0x5a } }
> +
>  [Ppis]
>    ## Include/Ppi/AtaController.h
>    gPeiAtaControllerPpiGuid       = { 0xa45e60d1, 0xc719, 0x44aa, { 0xb0, 0x7a, 0xaa, 0x77, 0x7f, 0x85, 0x90, 0x6d }}
> diff --git a/MdeModulePkg/Include/Guid/PlatformHasAcpi.h b/MdeModulePkg/Include/Guid/PlatformHasAcpi.h
> new file mode 100644
> index 000000000000..ad517821375d
> --- /dev/null
> +++ b/MdeModulePkg/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
> --
> 2.9.3
>
>