linux-kernel - [PATCH v2 1/4] arm64/sysreg: Fix checks for incomplete sysreg definitions

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Message-ID: <20251009165427.437379-2-sascha.bischoff@arm.com>
Date: Thu, 9 Oct 2025 16:54:47 +0000
From: Sascha Bischoff <Sascha.Bischoff@....com>
To: "linux-arm-kernel@...ts.infradead.org"
	<linux-arm-kernel@...ts.infradead.org>, "kvmarm@...ts.linux.dev"
	<kvmarm@...ts.linux.dev>, "linux-kernel@...r.kernel.org"
	<linux-kernel@...r.kernel.org>, "kvm@...r.kernel.org" <kvm@...r.kernel.org>
CC: nd <nd@....com>, Mark Rutland <Mark.Rutland@....com>, Mark Brown
	<broonie@...nel.org>, Catalin Marinas <Catalin.Marinas@....com>,
	"maz@...nel.org" <maz@...nel.org>, "oliver.upton@...ux.dev"
	<oliver.upton@...ux.dev>, Joey Gouly <Joey.Gouly@....com>, Suzuki Poulose
	<Suzuki.Poulose@....com>, "yuzenghui@...wei.com" <yuzenghui@...wei.com>,
	"will@...nel.org" <will@...nel.org>, "lpieralisi@...nel.org"
	<lpieralisi@...nel.org>
Subject: [PATCH v2 1/4] arm64/sysreg: Fix checks for incomplete sysreg
 definitions

The checks for incomplete sysreg definitions were checking if the
next_bit was greater than 0, which is incorrect and missed occasions
where bit 0 hasn't been defined for a sysreg. The reason is that
next_bit is -1 when all bits have been processed (LSB - 1).

Change the checks to use >= 0, instead. Also, set next_bit in Mapping
to -1 instead of 0 to match these new checks.

There are no changes to the generated sysreg definitons as part of
this change, and conveniently no definitions lack definitions for bit
0.

Signed-off-by: Sascha Bischoff <sascha.bischoff@....com>
---
 arch/arm64/tools/gen-sysreg.awk | 6 +++---
 1 file changed, 3 insertions(+), 3 deletions(-)

diff --git a/arch/arm64/tools/gen-sysreg.awk b/arch/arm64/tools/gen-sysreg.awk
index f2a1732cb1f63..c74d805a2aa38 100755
--- a/arch/arm64/tools/gen-sysreg.awk
+++ b/arch/arm64/tools/gen-sysreg.awk
@@ -129,7 +129,7 @@ $1 == "SysregFields" && block_current() == "Root" {
 
 $1 == "EndSysregFields" && block_current() == "SysregFields" {
 	expect_fields(1)
-	if (next_bit > 0)
+	if (next_bit >= 0)
 		fatal("Unspecified bits in " reg)
 
 	define(reg "_RES0", "(" res0 ")")
@@ -180,7 +180,7 @@ $1 == "Sysreg" && block_current() == "Root" {
 
 $1 == "EndSysreg" && block_current() == "Sysreg" {
 	expect_fields(1)
-	if (next_bit > 0)
+	if (next_bit >= 0)
 		fatal("Unspecified bits in " reg)
 
 	if (res0 != null)
@@ -217,7 +217,7 @@ $1 == "EndSysreg" && block_current() == "Sysreg" {
 	print "/* For " reg " fields see " $2 " */"
 	print ""
 
-        next_bit = 0
+        next_bit = -1
 	res0 = null
 	res1 = null
 	unkn = null
-- 
2.34.1