67bad2fdb7
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>
60 lines
1.8 KiB
C
60 lines
1.8 KiB
C
/*
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* Copyright (C) 2014 Linaro Ltd. <ard.biesheuvel@linaro.org>
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*
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* This program is free software; you can redistribute it and/or modify
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* it under the terms of the GNU General Public License version 2 as
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* published by the Free Software Foundation.
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*/
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#ifndef __LINUX_CPUFEATURE_H
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#define __LINUX_CPUFEATURE_H
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#ifdef CONFIG_GENERIC_CPU_AUTOPROBE
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#include <linux/mod_devicetable.h>
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#include <asm/cpufeature.h>
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/*
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* Macros imported from <asm/cpufeature.h>:
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* - cpu_feature(x) ordinal value of feature called 'x'
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* - cpu_have_feature(u32 n) whether feature #n is available
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* - MAX_CPU_FEATURES upper bound for feature ordinal values
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* Optional:
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* - CPU_FEATURE_TYPEFMT format string fragment for printing the cpu type
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* - CPU_FEATURE_TYPEVAL set of values matching the format string above
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*/
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#ifndef CPU_FEATURE_TYPEFMT
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#define CPU_FEATURE_TYPEFMT "%s"
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#endif
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#ifndef CPU_FEATURE_TYPEVAL
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#define CPU_FEATURE_TYPEVAL ELF_PLATFORM
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#endif
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/*
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* Use module_cpu_feature_match(feature, module_init_function) to
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* declare that
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* a) the module shall be probed upon discovery of CPU feature 'feature'
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* (typically at boot time using udev)
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* b) the module must not be loaded if CPU feature 'feature' is not present
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* (not even by manual insmod).
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*
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* For a list of legal values for 'feature', please consult the file
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* 'asm/cpufeature.h' of your favorite architecture.
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*/
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#define module_cpu_feature_match(x, __init) \
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static struct cpu_feature const cpu_feature_match_ ## x[] = \
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{ { .feature = cpu_feature(x) }, { } }; \
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MODULE_DEVICE_TABLE(cpu, cpu_feature_match_ ## x); \
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\
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static int cpu_feature_match_ ## x ## _init(void) \
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{ \
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if (!cpu_have_feature(cpu_feature(x))) \
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return -ENODEV; \
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return __init(); \
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} \
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module_init(cpu_feature_match_ ## x ## _init)
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#endif
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#endif
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