From 5b09f83e0c5635cac19ae3660d3d7bafb2416cd6 Mon Sep 17 00:00:00 2001
From: Savva Mitrofanov <savvamtr@gmail.com>
Date: Wed, 8 Feb 2023 21:47:04 +0600
Subject: [PATCH] FatPkg: Adds support for read-only mode

Implements gEfiFatPkgTokenSpaceGuid token space and adds token which
disables write operations. By default driver still supports read-write
mode

Signed-off-by: Savva Mitrofanov <savvamtr@gmail.com>
---
 FatPkg/EnhancedFatDxe/Fat.inf |  2 ++
 FatPkg/EnhancedFatDxe/Init.c  |  2 +-
 FatPkg/FatPkg.dec             | 13 +++++++++++++
 FatPkg/FatPkg.dsc             |  3 +++
 4 files changed, 19 insertions(+), 1 deletion(-)

diff --git a/FatPkg/EnhancedFatDxe/Fat.inf b/FatPkg/EnhancedFatDxe/Fat.inf
index 17b6348a25..92864278c4 100644
--- a/FatPkg/EnhancedFatDxe/Fat.inf
+++ b/FatPkg/EnhancedFatDxe/Fat.inf
@@ -56,6 +56,7 @@
 
 [Packages]
   MdePkg/MdePkg.dec
+  FatPkg/FatPkg.dec
 
 [LibraryClasses]
   UefiRuntimeServicesTableLib
@@ -82,6 +83,7 @@
   gEfiUnicodeCollation2ProtocolGuid     ## TO_START
 
 [Pcd]
+  gEfiFatPkgTokenSpaceGuid.PcdFatReadOnlyMode                   ## CONSUMES
   gEfiMdePkgTokenSpaceGuid.PcdUefiVariableDefaultLang           ## SOMETIMES_CONSUMES
   gEfiMdePkgTokenSpaceGuid.PcdUefiVariableDefaultPlatformLang   ## SOMETIMES_CONSUMES
 [UserExtensions.TianoCore."ExtraFiles"]
diff --git a/FatPkg/EnhancedFatDxe/Init.c b/FatPkg/EnhancedFatDxe/Init.c
index 208318c7ad..feae369693 100644
--- a/FatPkg/EnhancedFatDxe/Init.c
+++ b/FatPkg/EnhancedFatDxe/Init.c
@@ -51,7 +51,7 @@ FatAllocateVolume (
   Volume->DiskIo2                    = DiskIo2;
   Volume->BlockIo                    = BlockIo;
   Volume->MediaId                    = BlockIo->Media->MediaId;
-  Volume->ReadOnly                   = BlockIo->Media->ReadOnly;
+  Volume->ReadOnly                   = BlockIo->Media->ReadOnly || FeaturePcdGet (PcdFatReadOnlyMode);
   Volume->VolumeInterface.Revision   = EFI_SIMPLE_FILE_SYSTEM_PROTOCOL_REVISION;
   Volume->VolumeInterface.OpenVolume = FatOpenVolume;
   InitializeListHead (&Volume->CheckRef);
diff --git a/FatPkg/FatPkg.dec b/FatPkg/FatPkg.dec
index ecd086b41a..017402984a 100644
--- a/FatPkg/FatPkg.dec
+++ b/FatPkg/FatPkg.dec
@@ -17,3 +17,16 @@
 
 [UserExtensions.TianoCore."ExtraFiles"]
   FatPkgExtra.uni
+
+[Guids]
+  #
+  # GUID defined in package
+  #
+  gEfiFatPkgTokenSpaceGuid = { 0xbe1f59ff, 0x65f5, 0x4b28, {0xb2, 0x8d, 0x56, 0x85, 0x36, 0x4a, 0xb1, 0xd2 } }
+
+[PcdsFeatureFlag.common]
+  ## Indicates if driver is in read-only mode.<BR><BR>
+  #   TRUE  - Restricts write operations.<BR>
+  #   FALSE - Write operations allowed. Default behavior<BR>
+  # @Prompt Disables write operations on fat filesystem.
+  gEfiFatPkgTokenSpaceGuid.PcdFatReadOnlyMode |FALSE|BOOLEAN|0x00000001
diff --git a/FatPkg/FatPkg.dsc b/FatPkg/FatPkg.dsc
index 076b577972..e377c25ea1 100644
--- a/FatPkg/FatPkg.dsc
+++ b/FatPkg/FatPkg.dsc
@@ -82,3 +82,6 @@
 [Components]
   FatPkg/FatPei/FatPei.inf
   FatPkg/EnhancedFatDxe/Fat.inf
+
+[PcdsFeatureFlag]
+  gEfiFatPkgTokenSpaceGuid.PcdFatReadOnlyMode|FALSE