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>
diff --git a/drivers/base/cpu.c b/drivers/base/cpu.c
index f48370d..8a38bf8 100644
--- a/drivers/base/cpu.c
+++ b/drivers/base/cpu.c
@@ -15,6 +15,7 @@
#include <linux/percpu.h>
#include <linux/acpi.h>
#include <linux/of.h>
+#include <linux/cpufeature.h>
#include "base.h"
@@ -286,6 +287,45 @@
*/
}
+#ifdef CONFIG_HAVE_CPU_AUTOPROBE
+#ifdef CONFIG_GENERIC_CPU_AUTOPROBE
+static ssize_t print_cpu_modalias(struct device *dev,
+ struct device_attribute *attr,
+ char *buf)
+{
+ ssize_t n;
+ u32 i;
+
+ n = sprintf(buf, "cpu:type:" CPU_FEATURE_TYPEFMT ":feature:",
+ CPU_FEATURE_TYPEVAL);
+
+ for (i = 0; i < MAX_CPU_FEATURES; i++)
+ if (cpu_have_feature(i)) {
+ if (PAGE_SIZE < n + sizeof(",XXXX\n")) {
+ WARN(1, "CPU features overflow page\n");
+ break;
+ }
+ n += sprintf(&buf[n], ",%04X", i);
+ }
+ 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)
+{
+ char *buf = kzalloc(PAGE_SIZE, GFP_KERNEL);
+ if (buf) {
+ print_cpu_modalias(NULL, NULL, buf);
+ add_uevent_var(env, "MODALIAS=%s", buf);
+ kfree(buf);
+ }
+ return 0;
+}
+#endif
+
/*
* register_cpu - Setup a sysfs device for a CPU.
* @cpu - cpu->hotpluggable field set to 1 will generate a control file in
@@ -306,8 +346,8 @@
cpu->dev.offline_disabled = !cpu->hotpluggable;
cpu->dev.offline = !cpu_online(num);
cpu->dev.of_node = of_get_cpu_node(num, NULL);
-#ifdef CONFIG_ARCH_HAS_CPU_AUTOPROBE
- cpu->dev.bus->uevent = arch_cpu_uevent;
+#ifdef CONFIG_HAVE_CPU_AUTOPROBE
+ cpu->dev.bus->uevent = cpu_uevent;
#endif
cpu->dev.groups = common_cpu_attr_groups;
if (cpu->hotpluggable)
@@ -330,8 +370,8 @@
}
EXPORT_SYMBOL_GPL(get_cpu_device);
-#ifdef CONFIG_ARCH_HAS_CPU_AUTOPROBE
-static DEVICE_ATTR(modalias, 0444, arch_print_cpu_modalias, NULL);
+#ifdef CONFIG_HAVE_CPU_AUTOPROBE
+static DEVICE_ATTR(modalias, 0444, print_cpu_modalias, NULL);
#endif
static struct attribute *cpu_root_attrs[] = {
@@ -344,7 +384,7 @@
&cpu_attrs[2].attr.attr,
&dev_attr_kernel_max.attr,
&dev_attr_offline.attr,
-#ifdef CONFIG_ARCH_HAS_CPU_AUTOPROBE
+#ifdef CONFIG_HAVE_CPU_AUTOPROBE
&dev_attr_modalias.attr,
#endif
NULL
