linux-kernel - [PATCH] kbuild: give SUBLEVEL more room in KERNEL

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Date:   Sun, 17 Jan 2021 20:49:51 -0500
From:   Sasha Levin <sashal@...nel.org>
To:     masahiroy@...nel.org, michal.lkml@...kovi.net,
        torvalds@...ux-foundation.org
Cc:     linux-kbuild@...r.kernel.org, linux-kernel@...r.kernel.org,
        gregkh@...uxfoundation.org, Sasha Levin <sashal@...nel.org>,
        stable@...nel.org
Subject: [PATCH] kbuild: give SUBLEVEL more room in KERNEL_VERSION

SUBLEVEL only has 8 bits of space, which means that we'll overflow it
once it reaches 256.

Few of the stable branches will imminently overflow SUBLEVEL while
there's no risk of overflowing VERSION.

Thus, give SUBLEVEL 8 more bits which will be stolen from VERSION, this
should create a better balance between the different version numbers we
use.

The downside here is that Linus will have 8 bits less to play with, but
given our current release cadence (~10 weeks), the number of Linus's
fingers & toes (20), and the current VERSION (5) we can calculate that
VERSION will overflow in just over 1,000 years, so I'm kicking this can
down the road.

Cc: stable@...nel.org
Signed-off-by: Sasha Levin <sashal@...nel.org>
---
 Makefile | 4 ++--
 1 file changed, 2 insertions(+), 2 deletions(-)

diff --git a/Makefile b/Makefile
index 9e73f82e0d863..dc2bad7a440d8 100644
--- a/Makefile
+++ b/Makefile
@@ -1252,8 +1252,8 @@ endef

 define filechk_version.h
 	echo \#define LINUX_VERSION_CODE $(shell                         \
-	expr $(VERSION) \* 65536 + 0$(PATCHLEVEL) \* 256 + 0$(SUBLEVEL)); \
-	echo '#define KERNEL_VERSION(a,b,c) (((a) << 16) + ((b) << 8) + (c))'
+	expr $(VERSION) \* 16777216 + 0$(PATCHLEVEL) \* 65536 + 0$(SUBLEVEL)); \
+	echo '#define KERNEL_VERSION(a,b,c) (((a) << 24) + ((b) << 16) + (c))'
 endef

 $(version_h): FORCE
-- 
2.27.0