[PATCH v3 1/3] drm/xe: Add helpers for manipulating macro arguments

[Michal Wajdeczko <michal.wajdeczko@intel.com>]

Define generic helpers that will replace private definitions used
by the RTP code and will allow reuse by the new code.

Put them in new xe_args.h file (instead of infamous xe_macros.h)
as once we find more potential users outside of the Xe driver we
may want to move all of these macros as-is to linux/args.h.

Signed-off-by: Michal Wajdeczko <michal.wajdeczko@intel.com>
Cc: Andy Shevchenko <andriy.shevchenko@linux.intel.com>
Cc: Lucas De Marchi <lucas.demarchi@intel.com>
Reviewed-by: Lucas De Marchi <lucas.demarchi@intel.com>
---
v2: don't pollute linux/args.h yet (Andy)
v3: add explicit comment on future use inside the code (Lucas)
    fix include guard (Lucas)
---
 drivers/gpu/drm/xe/xe_args.h | 121 +++++++++++++++++++++++++++++++++++
 1 file changed, 121 insertions(+)
 create mode 100644 drivers/gpu/drm/xe/xe_args.h

diff --git a/drivers/gpu/drm/xe/xe_args.h b/drivers/gpu/drm/xe/xe_args.h
new file mode 100644
index 000000000000..40b9eb4151d8
--- /dev/null
+++ b/drivers/gpu/drm/xe/xe_args.h
@@ -0,0 +1,121 @@
+/* SPDX-License-Identifier: MIT */
+/*
+ * Copyright © 2024 Intel Corporation
+ */
+
+#ifndef _XE_ARGS_H_
+#define _XE_ARGS_H_
+
+#include <linux/args.h>
+
+/*
+ * Why don't the following macros have the XE prefix?
+ *
+ * Once we find more potential users outside of the Xe driver, we plan to move
+ * all of the following macros unchanged to linux/args.h.
+ */
+
+/**
+ * CALL_ARGS - Invoke a macro, but allow parameters to be expanded beforehand.
+ * @f: name of the macro to invoke
+ * @args: arguments for the macro
+ *
+ * This macro allows calling macros which names might generated or we want to
+ * make sure it's arguments will be correctly expanded.
+ *
+ * Example:
+ *
+ *	#define foo	X,Y,Z,Q
+ *	#define bar	COUNT_ARGS(foo)
+ *	#define buz	CALL_ARGS(COUNT_ARGS, foo)
+ *
+ *	With above definitions bar expands to 1 while buz expands to 4.
+ */
+#define CALL_ARGS(f, args...)		__CALL_ARGS(f, args)
+#define __CALL_ARGS(f, args...)		f(args)
+
+/**
+ * DROP_FIRST - Returns all arguments except the first one.
+ * @args: arguments
+ *
+ * This helper macro allows manipulation the argument list before passing it
+ * to the next level macro.
+ *
+ * Example:
+ *
+ *	#define foo	X,Y,Z,Q
+ *	#define bar	CALL_ARGS(COUNT_ARGS, DROP_FIRST(foo))
+ *
+ *	With above definitions bar expands to 3.
+ */
+#define DROP_FIRST(args...)		__DROP_FIRST(args)
+#define __DROP_FIRST(a, b...)		b
+
+/**
+ * PICK_FIRST - Returns the first argument.
+ * @args: arguments
+ *
+ * This helper macro allows manipulation the argument list before passing it
+ * to the next level macro.
+ *
+ * Example:
+ *
+ *	#define foo	X,Y,Z,Q
+ *	#define bar	PICK_FIRST(foo)
+ *
+ *	With above definitions bar expands to X.
+ */
+#define PICK_FIRST(args...)		__PICK_FIRST(args)
+#define __PICK_FIRST(a, b...)		a
+
+/**
+ * PICK_LAST - Returns the last argument.
+ * @args: arguments
+ *
+ * This helper macro allows manipulation the argument list before passing it
+ * to the next level macro.
+ *
+ * Like COUNT_ARGS() this macro works up to 12 arguments.
+ *
+ * Example:
+ *
+ *	#define foo	X,Y,Z,Q
+ *	#define bar	PICK_LAST(foo)
+ *
+ *	With above definitions bar expands to Q.
+ */
+#define PICK_LAST(args...)		__PICK_ARG(COUNT_ARGS(args), args)
+#define __PICK_ARG(n, args...)		CALL_ARGS(CONCATENATE(PICK_ARG, n), args)
+#define PICK_ARG1(args...)		PICK_FIRST(args)
+#define PICK_ARG2(args...)		PICK_ARG1(DROP_FIRST(args))
+#define PICK_ARG3(args...)		PICK_ARG2(DROP_FIRST(args))
+#define PICK_ARG4(args...)		PICK_ARG3(DROP_FIRST(args))
+#define PICK_ARG5(args...)		PICK_ARG4(DROP_FIRST(args))
+#define PICK_ARG6(args...)		PICK_ARG5(DROP_FIRST(args))
+#define PICK_ARG7(args...)		PICK_ARG6(DROP_FIRST(args))
+#define PICK_ARG8(args...)		PICK_ARG7(DROP_FIRST(args))
+#define PICK_ARG9(args...)		PICK_ARG8(DROP_FIRST(args))
+#define PICK_ARG10(args...)		PICK_ARG9(DROP_FIRST(args))
+#define PICK_ARG11(args...)		PICK_ARG10(DROP_FIRST(args))
+#define PICK_ARG12(args...)		PICK_ARG11(DROP_FIRST(args))
+
+/**
+ * ARGS_SEP_COMMA - Definition of a comma character.
+ *
+ * This definition can be used in cases where any intermediate macro expects
+ * fixed number of arguments, but we want to pass more arguments which can
+ * be properly evaluated only by the next level macro.
+ *
+ * Example:
+ *
+ *	#define foo(f)	f(X) f(Y) f(Z) f(Q)
+ *	#define bar	DROP_FIRST(foo(ARGS_SEP_COMMA __stringify))
+ *	#define buz	CALL_ARGS(COUNT_ARGS, DROP_FIRST(foo(ARGS_SEP_COMMA)))
+ *
+ *	With above definitions bar expands to
+ *		"X", "Y", "Z", "Q"
+ *	and buz expands to 4.
+ */
+#define ARGS_SEP_COMMA			,
+
+#endif
-- 
2.43.0