drm/xe: Add helpers for manipulating macro arguments

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>
Link: https://patchwork.freedesktop.org/patch/msgid/20240502223313.2527-2-michal.wajdeczko@intel.com

drivers/gpu/drm/xe/xe_args.h

+/* 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