linux-kernel - [PATCH] x86, bitops: select the generic bitmap search functions

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Date:	Fri, 25 Apr 2008 13:12:53 +0200
From:	Alexander van Heukelum <heukelum@...lshack.com>
To:	Linus Torvalds <torvalds@...ux-foundation.org>
Cc:	Ingo Molnar <mingo@...e.hu>, linux-kernel@...r.kernel.org,
	Sam Ravnborg <sam@...nborg.org>,
	Andrew Morton <akpm@...ux-foundation.org>,
	Thomas Gleixner <tglx@...utronix.de>,
	"H. Peter Anvin" <hpa@...or.com>
Subject: [PATCH] x86, bitops: select the generic bitmap search functions

Introduce GENERIC_FIND_FIRST_BIT and GENERIC_FIND_NEXT_BIT in
lib/Kconfig, defaulting to off. An arch that wants to use the
generic implementation now only has to use a select statement
to include them.

I added an always-y option (X86_CPU) to arch/x86/Kconfig.cpu
and used that to select the generic search functions. This
way ARCH=um SUBARCH=i386 automatically picks up the change
too, and arch/um/Kconfig.i386 can therefore be simplified a
bit. ARCH=um SUBARCH=x86_64 does things differently, but
still compiles fine. It seems that a "def_bool y" always
wins over a "def_bool n"?

Signed-off-by: Alexander van Heukelum <heukelum@...tmail.fm>

---

 arch/um/Kconfig.i386 |    8 --------
 arch/x86/Kconfig     |    6 ------
 arch/x86/Kconfig.cpu |    5 +++++
 lib/Kconfig          |    6 ++++++
 4 files changed, 11 insertions(+), 14 deletions(-)

Hello Linus,

I think this is close to what you had in mind?

The patch applies on top of:

git://git.kernel.org/pub/scm/linux/kernel/git/x86/linux-2.6-generic-bitops.git for-linus

Compile tested um/i386, um/x86_64. Boot-tested using
qemu for i386 and x86_64.

Greetings,
	Alexander

diff --git a/arch/um/Kconfig.i386 b/arch/um/Kconfig.i386
index 49990ea..e09edfa 100644
--- a/arch/um/Kconfig.i386
+++ b/arch/um/Kconfig.i386
@@ -39,14 +39,6 @@ config ARCH_REUSE_HOST_VSYSCALL_AREA
 	bool
 	default y
 
-config GENERIC_FIND_FIRST_BIT
-	bool
-	default y
-
-config GENERIC_FIND_NEXT_BIT
-	bool
-	default y
-
 config GENERIC_HWEIGHT
 	bool
 	default y
diff --git a/arch/x86/Kconfig b/arch/x86/Kconfig
index 004aad8..4d350b5 100644
--- a/arch/x86/Kconfig
+++ b/arch/x86/Kconfig
@@ -77,12 +77,6 @@ config GENERIC_BUG
 	def_bool y
 	depends on BUG
 
-config GENERIC_FIND_FIRST_BIT
-	def_bool y
-
-config GENERIC_FIND_NEXT_BIT
-	def_bool y
-
 config GENERIC_HWEIGHT
 	def_bool y
 
diff --git a/arch/x86/Kconfig.cpu b/arch/x86/Kconfig.cpu
index b9368f5..b94b04e 100644
--- a/arch/x86/Kconfig.cpu
+++ b/arch/x86/Kconfig.cpu
@@ -278,6 +278,11 @@ config GENERIC_CPU
 
 endchoice
 
+config X86_CPU
+	def_bool y
+	select GENERIC_FIND_FIRST_BIT
+	select GENERIC_FIND_NEXT_BIT
+
 config X86_GENERIC
 	bool "Generic x86 support"
 	depends on X86_32
diff --git a/lib/Kconfig b/lib/Kconfig
index 2d53dc0..8cc8e87 100644
--- a/lib/Kconfig
+++ b/lib/Kconfig
@@ -7,6 +7,12 @@ menu "Library routines"
 config BITREVERSE
 	tristate
 
+config GENERIC_FIND_FIRST_BIT
+	def_bool n
+
+config GENERIC_FIND_NEXT_BIT
+	def_bool n
+
 config CRC_CCITT
 	tristate "CRC-CCITT functions"
 	help
--
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