Re: [PATCH v2 05/12] ArmPkg: introduce EDKII Platform Has ACPI Protocol, and plug-in library

[Leif Lindholm <leif.lindholm@linaro.org>]

On Mon, Mar 20, 2017 at 10:01:09AM +0100, Laszlo Ersek wrote:
> >> Because this protocol is not standard, it is prefixed with EDKII / Edkii,
> >> as seen elsewhere in MdeModulePkg and SecurityPkg, for example. (ARM / Arm
> >> doesn't look future-proof enough; future UEFI platforms could face the
> >> same issue.) 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).
> > 
> > I greatly approve, but since you've already done this generically - is
> > there any good reason to keep this in ArmPkg?
> > I am strongly looking to get rid of "things that happen to have been
> > implemented for ARM" from there and pruning it down to contain only
> > things that are architecturelly ARM-specific.
> 
> This patch is not specific to ARM architecturally, but it is specific to
> the ARM ecosystem / community. I'm unaware of another platform (that
> would affect edk2 ATM anyway) where such a conflict in beliefs has not
> been sorted out for years.

Indeed. However, I have developed a mild allergy towards things that
are not fundamentally ARM-specific, but are treated as such.
It tends to introduce a mental barrier towards code unification and
sharing, since it makes it look like an architecture-specific component.

> The somewhat speculative generality in the naming (i.e., Edkii prefix
> rather than Arm) is there only because I understand that DT / libfdt is
> used on other platforms as well, and I expect once those see UEFI (and
> edk2) enablement & porting, the same DT vs. ACPI conflict in Linux space
> will extend to those platforms as well.
> 
> IOW, at the moment the patch is specific to ARM, it is not random, but
> it could change in the future. And, I wouldn't like to force client
> modules to rename the GUID at that time.

Oh, I perfectly agree.
I'm just saying I don't think that a feature only being applicable to
ARM at the current moment should be a barrier for it being introduced
in Mde*Pkg.

> > MdeModulePkg?
> 
> Not a bad idea, but the point of this approach was to avoid touching
> core modules. If we modify MdeModulePkg *logic* (as opposed to the
> trivial typo fix elsewhere in this series), then the simplest solution
> is to just add a dynamic PCD to MdeModulePkg.dec, which forces
> AcpiTableDxe to exit immediately with EFI_ABORTED or EFI_UNSUPPORTED.

That actually sounds more palatable to me than this set, which I still
prefer over Ard's solution (I'll expand on my reservations about that
one on the correct thread).

> As I mentioned earlier, PcdAcpiS3Enable had been introduced very
> similarly to this. It controls partial or full functionality of several
> DXE drivers:
> 
>   11a291a4d279 MdeModulePkg: Introduce new PCD PcdAcpiS3Enable
>   a1726e308903 OvmfPkg: Set PcdAcpiS3Enable according to
>                QemuFwCfgS3Enabled()
>   125e09387641 MdeModulePkg S3SaveStateDxe: Consume PcdAcpiS3Enable to
>                control the code
>   e96708de8837 IntelFrameworkModulePkg AcpiS3SaveDxe: Consume
>                PcdAcpiS3Enable to control the code
>   d2d38610603f MdeModulePkg SmmS3SaveStateDxe: Consume PcdAcpiS3Enable
>                to control the code
>   800c02fbe2da MdeModulePkg BootScriptExecutorDxe: Consume
>                PcdAcpiS3Enable to control the code
>   ca98f6038294 UefiCpuPkg/CpuS3DataDxe: Consume PcdAcpiS3Enable to
>                control the code
>   b10d5ddc0385 UefiCpuPkg/PiSmmCpuDxeSmm: Consume PcdAcpiS3Enable to
>                control the code
> 
> If the AcpiTableDxe maintainers aren't opposed to another dynamic PCD
> like PcdAcpiS3Enable -- but in this case for controlling AcpiTableDxe --
> then I'm fine with it too.
> 
> ... I knew that new PCDs in MdeModulePkg needed strong justification, so
> I figured I'd try another route first.

Yes, I understand. But I think it is well motivated here, and the
solution that feels the most UEFI to me.

Regards,

Leif

> Thanks
> Laszlo
> 
> > 
> > Regards,
> > 
> > Leif
> > 
> >> 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>
> >> ---
> >>  ArmPkg/ArmPkg.dec                                        |  4 ++
> >>  ArmPkg/Library/PlatformHasAcpiLib/PlatformHasAcpiLib.inf | 40 ++++++++++++++++++++
> >>  ArmPkg/Include/Protocol/PlatformHasAcpi.h                | 34 +++++++++++++++++
> >>  ArmPkg/Library/PlatformHasAcpiLib/PlatformHasAcpiLib.c   | 36 ++++++++++++++++++
> >>  4 files changed, 114 insertions(+)
> >>
> >> diff --git a/ArmPkg/ArmPkg.dec b/ArmPkg/ArmPkg.dec
> >> index c4b4da2f95bb..0e49360a386a 100644
> >> --- a/ArmPkg/ArmPkg.dec
> >> +++ b/ArmPkg/ArmPkg.dec
> >> @@ -52,6 +52,10 @@ [Ppis]
> >>    ## Include/Ppi/ArmMpCoreInfo.h
> >>    gArmMpCoreInfoPpiGuid = { 0x6847cc74, 0xe9ec, 0x4f8f, {0xa2, 0x9d, 0xab, 0x44, 0xe7, 0x54, 0xa8, 0xfc} }
> >>  
> >> +[Protocols]
> >> +  ## Include/Protocol/PlatformHasAcpi.h
> >> +  gEdkiiPlatformHasAcpiProtocolGuid =       { 0xf0966b41, 0xc23f, 0x41b9, { 0x96, 0x04, 0x0f, 0xf7, 0xe1, 0x11, 0x96, 0x5a } }
> >> +
> >>  [PcdsFeatureFlag.common]
> >>    gArmTokenSpaceGuid.PcdCpuDxeProduceDebugSupport|FALSE|BOOLEAN|0x00000001
> >>  
> >> diff --git a/ArmPkg/Library/PlatformHasAcpiLib/PlatformHasAcpiLib.inf b/ArmPkg/Library/PlatformHasAcpiLib/PlatformHasAcpiLib.inf
> >> new file mode 100644
> >> index 000000000000..c83da4d8e98a
> >> --- /dev/null
> >> +++ b/ArmPkg/Library/PlatformHasAcpiLib/PlatformHasAcpiLib.inf
> >> @@ -0,0 +1,40 @@
> >> +## @file
> >> +# A hook-in library for MdeModulePkg/Universal/Acpi/AcpiTableDxe.
> >> +#
> >> +# Plugging this library instance into AcpiTableDxe makes
> >> +# EFI_ACPI_TABLE_PROTOCOL and (if enabled) EFI_ACPI_SDT_PROTOCOL depend on the
> >> +# platform's dynamic decision whether to expose an ACPI-based hardware
> >> +# description to the operating system.
> >> +#
> >> +# Universal and platform specific DXE drivers that produce ACPI tables depend
> >> +# on EFI_ACPI_TABLE_PROTOCOL / EFI_ACPI_SDT_PROTOCOL in turn.
> >> +#
> >> +# 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 which 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.
> >> +##
> >> +
> >> +[Defines]
> >> +  INF_VERSION                    = 1.25
> >> +  BASE_NAME                      = PlatformHasAcpiLib
> >> +  FILE_GUID                      = 29beb028-0958-447b-be0a-12229235d77d
> >> +  MODULE_TYPE                    = BASE
> >> +  VERSION_STRING                 = 1.0
> >> +  LIBRARY_CLASS                  = PlatformHasAcpiLib|DXE_DRIVER
> >> +  CONSTRUCTOR                    = PlatformHasAcpiInitialize
> >> +
> >> +[Sources]
> >> +  PlatformHasAcpiLib.c
> >> +
> >> +[Packages]
> >> +  ArmPkg/ArmPkg.dec
> >> +  MdePkg/MdePkg.dec
> >> +
> >> +[Depex]
> >> +  gEdkiiPlatformHasAcpiProtocolGuid
> >> diff --git a/ArmPkg/Include/Protocol/PlatformHasAcpi.h b/ArmPkg/Include/Protocol/PlatformHasAcpi.h
> >> new file mode 100644
> >> index 000000000000..3cd0cfe4515d
> >> --- /dev/null
> >> +++ b/ArmPkg/Include/Protocol/PlatformHasAcpi.h
> >> @@ -0,0 +1,34 @@
> >> +/** @file
> >> +  EDKII Platform Has ACPI Protocol
> >> +
> >> +  The presence of this protocol in the DXE protocol database implies that the
> >> +  platform provides the operating system with an ACPI-based hardware
> >> +  description. Note that this is not necessarily mutually exclusive with a
> >> +  Device Tree-based hardware description. A platform driver is supposed to
> >> +  produce a single instance of the protocol (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_PROTOCOL_H__
> >> +#define __EDKII_PLATFORM_HAS_ACPI_PROTOCOL_H__
> >> +
> >> +#define EDKII_PLATFORM_HAS_ACPI_PROTOCOL_GUID \
> >> +  { \
> >> +    0xf0966b41, 0xc23f, 0x41b9, \
> >> +    { 0x96, 0x04, 0x0f, 0xf7, 0xe1, 0x11, 0x96, 0x5a } \
> >> +  }
> >> +
> >> +extern EFI_GUID gEdkiiPlatformHasAcpiProtocolGuid;
> >> +
> >> +#endif
> >> diff --git a/ArmPkg/Library/PlatformHasAcpiLib/PlatformHasAcpiLib.c b/ArmPkg/Library/PlatformHasAcpiLib/PlatformHasAcpiLib.c
> >> new file mode 100644
> >> index 000000000000..79072da21c2b
> >> --- /dev/null
> >> +++ b/ArmPkg/Library/PlatformHasAcpiLib/PlatformHasAcpiLib.c
> >> @@ -0,0 +1,36 @@
> >> +/** @file
> >> +  A hook-in library for MdeModulePkg/Universal/Acpi/AcpiTableDxe.
> >> +
> >> +  Plugging this library instance into AcpiTableDxe makes
> >> +  EFI_ACPI_TABLE_PROTOCOL and (if enabled) EFI_ACPI_SDT_PROTOCOL depend on the
> >> +  platform's dynamic decision whether to expose an ACPI-based hardware
> >> +  description to the operating system.
> >> +
> >> +  Universal and platform specific DXE drivers that produce ACPI tables depend
> >> +  on EFI_ACPI_TABLE_PROTOCOL / EFI_ACPI_SDT_PROTOCOL in turn.
> >> +
> >> +  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 which 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.
> >> +**/
> >> +
> >> +#include <Base.h>
> >> +
> >> +RETURN_STATUS
> >> +EFIAPI
> >> +PlatformHasAcpiInitialize (
> >> +  VOID
> >> +  )
> >> +{
> >> +  //
> >> +  // Do nothing, just imbue AcpiTableDxe with an
> >> +  // EDKII_PLATFORM_HAS_ACPI_PROTOCOL dependency.
> >> +  //
> >> +  return RETURN_SUCCESS;
> >> +}
> >> -- 
> >> 2.9.3
> >>
> >>
>