[Xen-devel] [PATCH v3 1/8] MdeModulePkg: introduce PcdPciDisableBusEnumeration

[Wei Liu <wei.liu2@xxxxxxxxxx>]

Platforms such as Xen already enumerates PCI bridges and devices. Use
this PCD to control EDK2 behavior.

PcdPciDisableBusEnumeration is placed under [PcdFixedAtBuild,
PcdDynamic, PcdDynamicEx], so that it is possible to alter it during
runtime.

The default setting of this PCD is false (allow full PCI enumeration) to
preserve the same behavior before this change.

Contributed-under: TianoCore Contribution Agreement 1.0
Signed-off-by: Wei Liu <wei.liu2@xxxxxxxxxx>
---
 MdeModulePkg/Bus/Pci/PciBusDxe/PciBus.c      |    5 ++++-
 MdeModulePkg/Bus/Pci/PciBusDxe/PciBusDxe.inf |    1 +
 MdeModulePkg/MdeModulePkg.dec                |    3 +++
 3 files changed, 8 insertions(+), 1 deletion(-)

diff --git a/MdeModulePkg/Bus/Pci/PciBusDxe/PciBus.c 
b/MdeModulePkg/Bus/Pci/PciBusDxe/PciBus.c
index 5afbb82..cc6be8b 100644
--- a/MdeModulePkg/Bus/Pci/PciBusDxe/PciBus.c
+++ b/MdeModulePkg/Bus/Pci/PciBusDxe/PciBus.c
@@ -284,7 +284,10 @@ PciBusDriverBindingStart (
           );
   }  
 
-  gFullEnumeration = (BOOLEAN) ((SearchHostBridgeHandle (Controller) ? FALSE : 
TRUE));
+  if (PcdGetBool (PcdPciDisableBusEnumeration))
+    gFullEnumeration = FALSE;
+  else
+    gFullEnumeration = (BOOLEAN) ((SearchHostBridgeHandle (Controller) ? FALSE 
: TRUE));
 
   //
   // Open Device Path Protocol for PCI root bridge
diff --git a/MdeModulePkg/Bus/Pci/PciBusDxe/PciBusDxe.inf 
b/MdeModulePkg/Bus/Pci/PciBusDxe/PciBusDxe.inf
index 34eb672..917889c 100644
--- a/MdeModulePkg/Bus/Pci/PciBusDxe/PciBusDxe.inf
+++ b/MdeModulePkg/Bus/Pci/PciBusDxe/PciBusDxe.inf
@@ -108,6 +108,7 @@
   gEfiMdeModulePkgTokenSpaceGuid.PcdSrIovSupport
   gEfiMdeModulePkgTokenSpaceGuid.PcdAriSupport
   gEfiMdeModulePkgTokenSpaceGuid.PcdMrIovSupport
+  gEfiMdeModulePkgTokenSpaceGuid.PcdPciDisableBusEnumeration
 
 # [Event]
 #   ##
diff --git a/MdeModulePkg/MdeModulePkg.dec b/MdeModulePkg/MdeModulePkg.dec
index b627eb1..e86868b 100644
--- a/MdeModulePkg/MdeModulePkg.dec
+++ b/MdeModulePkg/MdeModulePkg.dec
@@ -737,6 +737,9 @@
   ## This PCD specifies whether the Multi Root I/O virtualization support.
   gEfiMdeModulePkgTokenSpaceGuid.PcdMrIovSupport|FALSE|BOOLEAN|0x10000046
 
+  ## This PCD specifies whether full PCI enumeration is disabled.
+  
gEfiMdeModulePkgTokenSpaceGuid.PcdPciDisableBusEnumeration|FALSE|BOOLEAN|0x10000048
+
 [PcdsFixedAtBuild, PcdsPatchableInModule, PcdsDynamic, PcdsDynamicEx]
   ## Single root I/O virtualization virtual function memory BAR alignment
   #  BITN set indicates 2 of n+12 power
-- 
1.7.10.4


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