Re: [PATCH] SourceLevelDebugPkg/DebugAgentCommon: Use global variable for revision

["Ni, Ruiyu" <ruiyu.ni@intel.com>]

Yes. I agree with Mike's idea to use FixedAtBuild PCD for the debug agent transfer protocol revision.

-----Original Message-----
From: Wu, Hao A 
Sent: Wednesday, August 30, 2017 7:13 PM
To: Kinney, Michael D <michael.d.kinney@intel.com>; Ard Biesheuvel <ard.biesheuvel@linaro.org>
Cc: Ni, Ruiyu <ruiyu.ni@intel.com>; edk2-devel@lists.01.org
Subject: RE: [edk2] [PATCH] SourceLevelDebugPkg/DebugAgentCommon: Use global variable for revision

Thanks a lot for the feedbacks.

I will switch to using PCD for configuring revision and send out V2 of the patch.


Best Regards,
Hao Wu


> -----Original Message-----
> From: Kinney, Michael D
> Sent: Wednesday, August 30, 2017 12:00 AM
> To: Ard Biesheuvel; Wu, Hao A; Kinney, Michael D
> Cc: Ni, Ruiyu; edk2-devel@lists.01.org
> Subject: RE: [edk2] [PATCH] SourceLevelDebugPkg/DebugAgentCommon: Use 
> global variable for revision
> 
> Ard,
> 
> I agree.  Adding const would be an improvement too.
> 
> But I would prefer to not add a global variable at all.
> 
> When could this check ever evaluate to false?  Compression has been 
> supported for a long time now.
> 
> It appears that a developer would have to modify 
> SourceLevelDebugPkg\Include\TransferProtocol.h to select an older 
> protocol revision.
> 
> If we really want build configuration of the protocol revision then we 
> should use a PCD feature flag or a FixedAtBuild PCD to allow the 
> developer to configure it from the DSC file.
> 
> Mike
> 
> > -----Original Message-----
> > From: edk2-devel [mailto:edk2-devel-bounces@lists.01.org] On Behalf 
> > Of Ard Biesheuvel
> > Sent: Tuesday, August 29, 2017 8:01 AM
> > To: Wu, Hao A <hao.a.wu@intel.com>
> > Cc: Ni, Ruiyu <ruiyu.ni@intel.com>; edk2-devel@lists.01.org
> > Subject: Re: [edk2] [PATCH]
> > SourceLevelDebugPkg/DebugAgentCommon: Use global variable for 
> > revision
> >
> > On 29 August 2017 at 14:09, Hao Wu <hao.a.wu@intel.com> wrote:
> > > Since some static code checkers complain that comparing two
> > macros will
> > > generate a constant result, this commit uses a global
> > variable to
> > > reflect the revision information of the debug agent, rather
> > than using a
> > > macro directly.
> > >
> > > Cc: Ruiyu Ni <ruiyu.ni@intel.com>
> > > Contributed-under: TianoCore Contribution Agreement 1.1
> > > Signed-off-by: Hao Wu <hao.a.wu@intel.com>
> > > ---
> > >  .../Library/DebugAgent/DebugAgentCommon/DebugAgent.c
> > | 7 ++++---
> > >  1 file changed, 4 insertions(+), 3 deletions(-)
> > >
> > > diff --git
> > a/SourceLevelDebugPkg/Library/DebugAgent/DebugAgentCommon/Debug
> > Agent.c
> > b/SourceLevelDebugPkg/Library/DebugAgent/DebugAgentCommon/Debug
> > Agent.c
> > > index f156fe24db..93af009f96 100644
> > > ---
> > a/SourceLevelDebugPkg/Library/DebugAgent/DebugAgentCommon/Debug
> > Agent.c
> > > +++
> > b/SourceLevelDebugPkg/Library/DebugAgent/DebugAgentCommon/Debug
> > Agent.c
> > > @@ -130,7 +130,8 @@ GLOBAL_REMOVE_IF_UNREFERENCED
> > EFI_VECTOR_HANDOFF_INFO mVectorHandoffInfoDebugAge
> > >    }
> > >  };
> > >
> > > -GLOBAL_REMOVE_IF_UNREFERENCED UINTN mVectorHandoffInfoCount
> > = sizeof (mVectorHandoffInfoDebugAgent) / sizeof 
> > (EFI_VECTOR_HANDOFF_INFO);
> > > +GLOBAL_REMOVE_IF_UNREFERENCED UINTN  mVectorHandoffInfoCount
> > = sizeof (mVectorHandoffInfoDebugAgent) / sizeof 
> > (EFI_VECTOR_HANDOFF_INFO);
> > > +GLOBAL_REMOVE_IF_UNREFERENCED UINT32 mDebugAgentRevision
> > = DEBUG_AGENT_REVISION;
> > >
> > >  /**
> > >    Calculate CRC16 for target data.
> > > @@ -1564,7 +1565,7 @@ ReadMemoryAndSendResponsePacket (
> > >      // Compression/decompression support was added since
> > revision 0.4.
> > >      // Revision 0.3 shouldn't compress the packet.
> > >      //
> > > -    if (DEBUG_AGENT_REVISION >= DEBUG_AGENT_REVISION_04) {
> > > +    if (mDebugAgentRevision >= DEBUG_AGENT_REVISION_04) {
> > >        //
> > >        // Get the compressed data size without modifying the
> > packet.
> > >        //
> > > @@ -2192,7 +2193,7 @@ CommandCommunication (
> > >        break;
> > >
> > >      case DEBUG_COMMAND_GET_REVISION:
> > > -      DebugAgentRevision.Revision = DEBUG_AGENT_REVISION;
> > > +      DebugAgentRevision.Revision = mDebugAgentRevision;
> > >        DebugAgentRevision.Capabilities =
> > DEBUG_AGENT_CAPABILITIES;
> > >        Status = SendDataResponsePacket ((UINT8 *)
> > &DebugAgentRevision, (UINT16) sizeof 
> > (DEBUG_DATA_RESPONSE_GET_REVISION), DebugHeader);
> > >        break;
> > > --
> > > 2.12.0.windows.1
> > >
> >
> > Can we *please* fix the tools instead? mDebugAgentRevision has 
> > external linkage, and so the compiler is forced to perform this 
> > check at runtime instead of at build time. Or at least use a STATIC 
> > variable so the compiler can see that mDebugAgentRevision is never 
> > modified from its default value.
> > _______________________________________________
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