include/asm-offsets.h: automatically generate assembler constants

A recurrent issue is that certain C level constructs like sizeof() or
offsetof() cannot be used in assembler files, which is inconvenient
when such constructs are used in the definition of macro names etc.

To avoid duplication of such definitions (and thus another cause of
problems), we adapt the Linux way to automatically generate the
respective definitions from the respective C header files.

In Linux, this is implemented in include/linux/kbuild.h, Kbuild, and
arch/*/kernel/asm-offsets.c; we adapt the code from the Linux v2.6.36
kernel tree.

We also copy the concept of the include/generated/ directory which can
be used to hold other automatically generated files as well.

We start with an architecture-independent lib/asm-offsets.c which
generates include/generated/generic-asm-offsets.h (included by
include/asm-offsets.h, which is what will be referred to in the actual
source code).  Later this may be extended by architecture-specific
arch/*/lib/asm-offsets.c files that will generate a
include/generated/asm-offsets.h.

Signed-off-by: Wolfgang Denk <wd@denx.de>
Acked-by: Kumar Gala <galak@kernel.crashing.org>

1 files changed, 20 insertions, 0 deletions

diff --git a/include/linux/kbuild.h b/include/linux/kbuild.h
new file mode 100644
index 0000000..be76384
--- /dev/null
+++ b/include/linux/kbuild.h
@@ -0,0 +1,20 @@
+/*
+ * Copied from Linux:
+ * commit 37487a56523d402e25650da16c337acf4cecd13d
+ * Author: Christoph Lameter <clameter@sgi.com>
+ */
+#ifndef __LINUX_KBUILD_H
+#define __LINUX_KBUILD_H
+
+#define DEFINE(sym, val) \
+        asm volatile("\n->" #sym " %0 " #val : : "i" (val))
+
+#define BLANK() asm volatile("\n->" : : )
+
+#define OFFSET(sym, str, mem) \
+	DEFINE(sym, offsetof(struct str, mem))
+
+#define COMMENT(x) \
+	asm volatile("\n->#" x)
+
+#endif