arch/arm/include/asm/cpufeature.h

   1 /*
   2  * Copyright (C) 2017 Linaro Ltd. <ard.biesheuvel@linaro.org>
   3  *
   4  * This program is free software; you can redistribute it and/or modify
   5  * it under the terms of the GNU General Public License version 2 as
   6  * published by the Free Software Foundation.
   7  */
   8
   9 #ifndef __ASM_CPUFEATURE_H
  10 #define __ASM_CPUFEATURE_H
  11
  12 #include <linux/log2.h>
  13 #include <asm/hwcap.h>
  14
  15 /*
  16  * Due to the fact that ELF_HWCAP is a 32-bit type on ARM, and given the number
  17  * of optional CPU features it defines, ARM's CPU hardware capability bits have
  18  * been distributed over separate elf_hwcap and elf_hwcap2 variables, each of
  19  * which covers a subset of the available CPU features.
  20  *
  21  * Currently, only a few of those are suitable for automatic module loading
  22  * (which is the primary use case of this facility) and those happen to be all
  23  * covered by HWCAP2. So let's only cover those via the cpu_feature()
  24  * convenience macro for now (which is used by module_cpu_feature_match()).
  25  * However, all capabilities are exposed via the modalias, and can be matched
  26  * using an explicit MODULE_DEVICE_TABLE() that uses __hwcap_feature() directly.
  27  */
  28 #define MAX_CPU_FEATURES        64
  29 #define __hwcap_feature(x)      ilog2(HWCAP_ ## x)
  30 #define __hwcap2_feature(x)     (32 + ilog2(HWCAP2_ ## x))
  31 #define cpu_feature(x)          __hwcap2_feature(x)
  32
  33 static inline bool cpu_have_feature(unsigned int num)
  34 {
  35         return num < 32 ? elf_hwcap & BIT(num) : elf_hwcap2 & BIT(num - 32);
  36 }
  37
  38 #endif