From: David Sterba <dsterba@suse.com>
Date: Fri, 9 Sep 2022 15:20:25 +0000 (+0200)
Subject: btrfs: add helper for bit enumeration
X-Git-Tag: v6.6.17~5604^2~236
X-Git-Url: http://review.tizen.org/git/?a=commitdiff_plain;h=d549ff7bdbe72f5e0e934895090fed2647e9813b;p=platform%2Fkernel%2Flinux-rpi.git

btrfs: add helper for bit enumeration

Define helper macro that can be used in enum {} to utilize the automatic
increment to define all bits without directly defining the values or
using additional linear bits.

1. capture the sequence value, N
2. use the value to define the given enum with N-th bit set
3. reset the sequence back to N

Use for enums that do not require fixed values for symbolic names (like
for on-disk structures):

enum {
	ENUM_BIT(FIRST),
	ENUM_BIT(SECOND),
	ENUM_BIT(THIRD)
};

Where the values would be 0x1, 0x2 and 0x4.

Reviewed-by: Josef Bacik <josef@toxicpanda.com>
Signed-off-by: David Sterba <dsterba@suse.com>
---

diff --git a/fs/btrfs/misc.h b/fs/btrfs/misc.h
index f9850edf..69826cc 100644
--- a/fs/btrfs/misc.h
+++ b/fs/btrfs/misc.h
@@ -10,6 +10,14 @@
 
 #define in_range(b, first, len) ((b) >= (first) && (b) < (first) + (len))
 
+/*
+ * Enumerate bits using enum autoincrement. Define the @name as the n-th bit.
+ */
+#define ENUM_BIT(name)                                  \
+	__ ## name ## _BIT,                             \
+	name = (1U << __ ## name ## _BIT),              \
+	__ ## name ## _SEQ = __ ## name ## _BIT
+
 static inline void cond_wake_up(struct wait_queue_head *wq)
 {
 	/*