kernel.h: split out COUNT_ARGS() and CONCATENATE() to args.h

Patch series "kernel.h: Split out a couple of macros to args.h", v4.

There are macros in kernel.h that can be used outside of that header. 
Split them to args.h and replace open coded variants.


This patch (of 4):

kernel.h is being used as a dump for all kinds of stuff for a long time. 
The COUNT_ARGS() and CONCATENATE() macros may be used in some places
without need of the full kernel.h dependency train with it.

Here is the attempt on cleaning it up by splitting out these macros().

While at it, include new header where it's being used.

Link: https://lkml.kernel.org/r/20230718211147.18647-1-andriy.shevchenko@linux.intel.com
Link: https://lkml.kernel.org/r/20230718211147.18647-2-andriy.shevchenko@linux.intel.com
Signed-off-by: Andy Shevchenko <andriy.shevchenko@linux.intel.com>
Acked-by: Steven Rostedt (Google) <rostedt@goodmis.org>
Cc: Bjorn Helgaas <bhelgaas@google.com>
Acked-by: Bjorn Helgaas <bhelgaas@google.com>	[PCI]
Cc: Brendan Higgins <brendan.higgins@linux.dev>
Cc: Daniel Latypov <dlatypov@google.com>
Cc: Dave Hansen <dave.hansen@linux.intel.com>
Cc: David Gow <davidgow@google.com>
Cc: "H. Peter Anvin" <hpa@zytor.com>
Cc: Ingo Molnar <mingo@redhat.com>
Cc: Lorenzo Pieralisi <lpieralisi@kernel.org>
Cc: Mark Rutland <mark.rutland@arm.com>
Cc: Masami Hiramatsu (Google) <mhiramat@kernel.org>
Cc: Shuah Khan <skhan@linuxfoundation.org>
Cc: Sudeep Holla <sudeep.holla@arm.com>
Cc: Thomas Gleixner <tglx@linutronix.de>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>

1 files changed, 28 insertions, 0 deletions

diff --git a/include/linux/args.h b/include/linux/args.h
new file mode 100644
index 000000000000..8ff60a54eb7d
--- /dev/null
+++ b/include/linux/args.h
@@ -0,0 +1,28 @@
+/* SPDX-License-Identifier: GPL-2.0 */
+
+#ifndef _LINUX_ARGS_H
+#define _LINUX_ARGS_H
+
+/*
+ * How do these macros work?
+ *
+ * In __COUNT_ARGS() _0 to _12 are just placeholders from the start
+ * in order to make sure _n is positioned over the correct number
+ * from 12 to 0 (depending on X, which is a variadic argument list).
+ * They serve no purpose other than occupying a position. Since each
+ * macro parameter must have a distinct identifier, those identifiers
+ * are as good as any.
+ *
+ * In COUNT_ARGS() we use actual integers, so __COUNT_ARGS() returns
+ * that as _n.
+ */
+
+/* This counts to 12. Any more, it will return 13th argument. */
+#define __COUNT_ARGS(_0, _1, _2, _3, _4, _5, _6, _7, _8, _9, _10, _11, _12, _n, X...) _n
+#define COUNT_ARGS(X...) __COUNT_ARGS(, ##X, 12, 11, 10, 9, 8, 7, 6, 5, 4, 3, 2, 1, 0)
+
+/* Concatenate two parameters, but allow them to be expanded beforehand. */
+#define __CONCAT(a, b) a ## b
+#define CONCATENATE(a, b) __CONCAT(a, b)
+
+#endif	/* _LINUX_ARGS_H */