RE: [RFC V6 2/3] add CONFIG_HAVE_ARCH_BITREVERSE to support rbit instruction

From: Wang, Yalin
Subject: [RFC V6 2/3] add CONFIG_HAVE_ARCH_BITREVERSE to support rbit
instruction

This patch add bitrev.h file to support rbit instruction, so that we can do
bitrev operation by hardware.
Signed-off-by: Yalin Wang <redacted>
---
 arch/arm/Kconfig              |  1 +
 arch/arm/include/asm/bitrev.h | 21 +++++++++++++++++++++
 2 files changed, 22 insertions(+)
 create mode 100644 arch/arm/include/asm/bitrev.h

diff --git a/arch/arm/Kconfig b/arch/arm/Kconfig index 89c4b5c..be92b3b

100644

--- a/arch/arm/Kconfig
+++ b/arch/arm/Kconfig

@@ -28,6 +28,7 @@ config ARM
 	select HANDLE_DOMAIN_IRQ
 	select HARDIRQS_SW_RESEND
 	select HAVE_ARCH_AUDITSYSCALL if (AEABI && !OABI_COMPAT)
+	select HAVE_ARCH_BITREVERSE if (CPU_V7M || CPU_V7)
 	select HAVE_ARCH_JUMP_LABEL if !XIP_KERNEL
 	select HAVE_ARCH_KGDB
 	select HAVE_ARCH_SECCOMP_FILTER if (AEABI && !OABI_COMPAT) diff --git

a/arch/arm/include/asm/bitrev.h b/arch/arm/include/asm/bitrev.h new file
mode 100644 index 0000000..e9b2571

--- /dev/null
+++ b/arch/arm/include/asm/bitrev.h

@@ -0,0 +1,21 @@
+#ifndef __ASM_ARM_BITREV_H
+#define __ASM_ARM_BITREV_H
+
+static __always_inline __attribute_const__ u32 __arch_bitrev32(u32 x) {
+	__asm__ ("rbit %0, %1" : "=r" (x) : "r" (x));
+	return x;
+}
+
+static __always_inline __attribute_const__ u16 __arch_bitrev16(u16 x) {
+	return __arch_bitrev32((u32)x) >> 16;
+}
+
+static __always_inline __attribute_const__ u8 __arch_bitrev8(u8 x) {
+	return __arch_bitrev32((u32)x) >> 24;
+}
+
+#endif
+
--

2.1.1