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Commit 9025d688 authored by Ard Biesheuvel's avatar Ard Biesheuvel Committed by Ruchi Kandoi
Browse files

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.

Change-Id: Icae8e3ff347235fc72a5b41279f0afdb34fb161a
Signed-off-by: default avatarArd Biesheuvel <ard.biesheuvel@linaro.org>
Signed-off-by: default avatarGreg Kroah-Hartman <gregkh@linuxfoundation.org>
parent 83d452a0

drivers/base/Kconfig

+5 −0
Original line number Diff line number Diff line
@@ -220,8 +220,13 @@ config GENERIC_CPU_DEVICES 
	bool

	default n



config HAVE_CPU_AUTOPROBE

	def_bool ARCH_HAS_CPU_AUTOPROBE



config GENERIC_CPU_AUTOPROBE

	bool

	depends on !ARCH_HAS_CPU_AUTOPROBE

	select HAVE_CPU_AUTOPROBE



config SOC_BUS

	bool

drivers/base/cpu.c

+7 −3
Original line number Diff line number Diff line
@@ -287,6 +287,7 @@ static void cpu_device_release(struct device *dev) 
	 */

}



#ifdef CONFIG_HAVE_CPU_AUTOPROBE

#ifdef CONFIG_GENERIC_CPU_AUTOPROBE

static ssize_t print_cpu_modalias(struct device *dev,

				  struct device_attribute *attr,
@@ -309,6 +310,9 @@ static ssize_t print_cpu_modalias(struct device *dev, 
	buf[n++] = '\n';

	return n;

}

#else

#define print_cpu_modalias	arch_print_cpu_modalias

#endif



static int cpu_uevent(struct device *dev, struct kobj_uevent_env *env)

{
@@ -342,7 +346,7 @@ int register_cpu(struct cpu *cpu, int num) 
	cpu->dev.offline_disabled = !cpu->hotpluggable;

	cpu->dev.offline = !cpu_online(num);

	cpu->dev.of_node = of_get_cpu_node(num, NULL);

#ifdef CONFIG_GENERIC_CPU_AUTOPROBE

#ifdef CONFIG_ARCH_HAS_CPU_AUTOPROBE

	cpu->dev.bus->uevent = cpu_uevent;

#endif

	cpu->dev.groups = common_cpu_attr_groups;
@@ -366,7 +370,7 @@ struct device *get_cpu_device(unsigned cpu) 
}

EXPORT_SYMBOL_GPL(get_cpu_device);



#ifdef CONFIG_GENERIC_CPU_AUTOPROBE

#ifdef CONFIG_HAVE_CPU_AUTOPROBE

static DEVICE_ATTR(modalias, 0444, print_cpu_modalias, NULL);

#endif
@@ -380,7 +384,7 @@ static struct attribute *cpu_root_attrs[] = { 
	&cpu_attrs[2].attr.attr,

	&dev_attr_kernel_max.attr,

	&dev_attr_offline.attr,

#ifdef CONFIG_GENERIC_CPU_AUTOPROBE

#ifdef CONFIG_HAVE_CPU_AUTOPROBE

	&dev_attr_modalias.attr,

#endif

	NULL