Add missing file

git-svn-id: https://edk2.svn.sourceforge.net/svnroot/edk2/trunk/edk2@5163 6f19259b-4bc3-4df7-8a09-765794883524

1 files changed, 134 insertions, 0 deletions

diff --git a/DuetPkg/CpuIoDxe/Ia32/CpuIoAccessGNU.c b/DuetPkg/CpuIoDxe/Ia32/CpuIoAccessGNU.c
new file mode 100644
index 0000000000..6c7b198d76
--- /dev/null
+++ b/DuetPkg/CpuIoDxe/Ia32/CpuIoAccessGNU.c
@@ -0,0 +1,134 @@
+/*  This file is only used when not able to compile the MASM CpuIoAccess.asm

+    NOTE: Compiling with -fomit-frame-pointer would get you to roughly the exact

+    same code as the MASM file although GCC will typically include movzbl %al, %eax

+    or movzwl %ax, %eax instructions on the read functions such that the entire

+    eax result register will be valid, not just the lowest 8 or 16 bits.

+ */

+#ifdef __GNUC__

+

+/*  A quick note about GCC inline asm and the GNU assembler:

+    When gas encounters an instruction with a suffix (e.g. inb, inw, or inl vs. just in) it will

+    warn if the operand corresponding to the suffix is not of the correct size and will assume you

+    meant what you said when you specified the suffix.

+

+    Because GCC does not enable us to see whether it is replacing %0 with %al, %ax, or %eax it is

+    helpful to have the assembler warn us that GCC is making an incorrect assumption.  The actual

+    in or out instruction will always be generated correctly in this case since the assembler is

+    correct in assuming we meant what we said when we specified the suffix.  However, GCC might

+    generate incorrect surrounding code.  For example, if we were to incorrectly specify the

+    output size of an in instruction as UINT32, GCC would potentially fail to issue movz(b|w)l after

+    it under the assumption that the in instruction filled the entire eax register and not just

+    the al or ax portion.

+

+    GCC determines which size of register to use based on the C data type.  So for in instructions

+    the interesting type is that of the automatic variable named Data which is specified as an

+    output operand to the inline assembly statement.  For example:

+

+      UINT8     Data;

+      asm ( "inb %1, %0"

+          : "=a"(Data)

+          : "d"(Port)

+          );

+      return Data;

+

+    In this case, GCC will replace %0 with %al.  If Data had been specified as UINT16, it would replace

+    %0 with %ax, and for UINT32 with %eax.

+

+    Likewise in the case of IA32 out instructions, GCC will replace %0 with the appropriately sized

+    register based on the size of the input operand.  There is one gotcha though.  The CpuIoWrite

+    series of functions all use UINT32 as the type of the second (Data) argument.  This means that

+    for GCC to output the correct register size we must cast it appropriately.

+

+    The Port number is always a UINT16 so GCC will always ouput %dx.

+ */

+

+#include "CpuIoAccess.h"

+

+UINT8

+IA32API

+CpuIoRead8 (

+  IN  UINT16  Port

+  )

+{

+  UINT8     Data;

+  asm ( "inb %1, %0"

+      : "=a"(Data)

+      : "d"(Port)

+      );

+  return Data;

+}

+

+UINT16

+IA32API

+CpuIoRead16 (

+  IN  UINT16  Port

+  )

+{

+  UINT16    Data;

+  asm ( "inw %1, %0"

+      : "=a"(Data)

+      : "d"(Port)

+      );

+  return Data;

+}

+

+UINT32

+IA32API

+CpuIoRead32 (

+  IN  UINT16  Port

+  )

+{

+  UINT32    Data;

+  asm ( "inl %1, %0"

+      : "=a"(Data)

+      : "d"(Port)

+      );

+  return Data;

+}

+

+VOID

+IA32API

+CpuIoWrite8 (

+  IN  UINT16  Port,

+  IN  UINT32  Data

+  )

+{

+  asm ( "outb %1, %0"

+      : /* No outputs */

+      : "d"(Port)

+      , "a"((UINT8)Data)

+      );

+}

+

+VOID

+IA32API

+CpuIoWrite16 (

+  IN  UINT16  Port,

+  IN  UINT32  Data

+  )

+{

+  asm ( "outw %1, %0"

+      : /* No outputs */

+      : "d"(Port)

+      , "a"((UINT16)Data)

+      );

+}

+

+VOID

+IA32API

+CpuIoWrite32 (

+  IN  UINT16  Port,

+  IN  UINT32  Data

+  )

+{

+  asm ( "outl %1, %0"

+      : /* No outputs */

+      : "d"(Port)

+      /*  NOTE: Cast is technically unnecessary but we use it to illustrate

+          that we always want to output a UINT32 and never anything else.

+       */

+      , "a"((UINT32)Data) 

+      );

+}

+

+#endif /* def __GNUC__ */