arm64: kernel: Add cpuid_feature_extract_field() for 4bit sign extension

Based on arch/arm/include/asm/cputype.h, this function does the
shifting and sign extension necessary when accessing cpu feature fields.

Signed-off-by: James Morse <[email protected]>
Suggested-by: Russell King <[email protected]>
Acked-by: Catalin Marinas <[email protected]>
Signed-off-by: Will Deacon <[email protected]>

diff --git a/arch/arm64/include/asm/cpufeature.h b/arch/arm64/include/asm/cpufeature.h
index c1044218a63a1598051d3d02b58d3241ec810cc1..9fafa7537997615e4996f992e7410c025cd679fb 100644 (file)
--- a/arch/arm64/include/asm/cpufeature.h
+++ b/arch/arm64/include/asm/cpufeature.h
@@ -70,6 +70,13 @@ static inline void cpus_set_cap(unsigned int num)
                __set_bit(num, cpu_hwcaps);
 }
 
+static inline int __attribute_const__ cpuid_feature_extract_field(u64 features,
+                                                                 int field)
+{
+       return (s64)(features << (64 - 4 - field)) >> (64 - 4);
+}
+
+
 void check_cpu_capabilities(const struct arm64_cpu_capabilities *caps,
                            const char *info);
 void check_local_cpu_errata(void);