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linux-next/include/linux/cpufeature.h
Ard Biesheuvel 67bad2fdb7 cpu: add generic support for CPU feature based module autoloading
This patch adds support for advertising optional CPU features over udev
using the modalias, and for declaring compatibility with/dependency upon
such a feature in a module.

The mapping between feature numbers and actual features should be provided
by the architecture in a file called <asm/cpufeature.h> which exports the
following functions/macros:
- cpu_feature(FEAT), a preprocessor macro that maps token FEAT to a
  numeric index;
- bool cpu_have_feature(n), returning whether this CPU has support for
  feature #n;
- MAX_CPU_FEATURES, an upper bound for 'n' in the previous function.

The feature can then be enabled by setting CONFIG_GENERIC_CPU_AUTOPROBE
for the architecture.

For instance, a module that registers its module init function using

  module_cpu_feature_match(FEAT_X, module_init_function)

will be probed automatically when the CPU's support for the 'FEAT_X'
feature is advertised over udev, and will only allow the module to be
loaded by hand if the 'FEAT_X' feature is supported.

Signed-off-by: Ard Biesheuvel <ard.biesheuvel@linaro.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
2014-02-18 12:38:37 -08:00

61 lines
1.8 KiB
C

/*
* Copyright (C) 2014 Linaro Ltd. <ard.biesheuvel@linaro.org>
*
* This program is free software; you can redistribute it and/or modify
* it under the terms of the GNU General Public License version 2 as
* published by the Free Software Foundation.
*/
#ifndef __LINUX_CPUFEATURE_H
#define __LINUX_CPUFEATURE_H
#ifdef CONFIG_GENERIC_CPU_AUTOPROBE
#include <linux/mod_devicetable.h>
#include <asm/cpufeature.h>
/*
* Macros imported from <asm/cpufeature.h>:
* - cpu_feature(x) ordinal value of feature called 'x'
* - cpu_have_feature(u32 n) whether feature #n is available
* - MAX_CPU_FEATURES upper bound for feature ordinal values
* Optional:
* - CPU_FEATURE_TYPEFMT format string fragment for printing the cpu type
* - CPU_FEATURE_TYPEVAL set of values matching the format string above
*/
#ifndef CPU_FEATURE_TYPEFMT
#define CPU_FEATURE_TYPEFMT "%s"
#endif
#ifndef CPU_FEATURE_TYPEVAL
#define CPU_FEATURE_TYPEVAL ELF_PLATFORM
#endif
/*
* Use module_cpu_feature_match(feature, module_init_function) to
* declare that
* a) the module shall be probed upon discovery of CPU feature 'feature'
* (typically at boot time using udev)
* b) the module must not be loaded if CPU feature 'feature' is not present
* (not even by manual insmod).
*
* For a list of legal values for 'feature', please consult the file
* 'asm/cpufeature.h' of your favorite architecture.
*/
#define module_cpu_feature_match(x, __init) \
static struct cpu_feature const cpu_feature_match_ ## x[] = \
{ { .feature = cpu_feature(x) }, { } }; \
MODULE_DEVICE_TABLE(cpu, cpu_feature_match_ ## x); \
\
static int cpu_feature_match_ ## x ## _init(void) \
{ \
if (!cpu_have_feature(cpu_feature(x))) \
return -ENODEV; \
return __init(); \
} \
module_init(cpu_feature_match_ ## x ## _init)
#endif
#endif