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cpu: add generic support for CPU feature based module autoloading

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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>
This commit is contained in:
Ard Biesheuvel 2014-02-08 13:34:09 +01:00 • committed by Greg Kroah-Hartman
parent 91219a3b20
commit 67bad2fdb7
6 changed files with 135 additions and 5 deletions
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10
scripts/mod/file2alias.c
View file

@ -1135,6 +1135,16 @@ static int do_x86cpu_entry(const char *filename, void *symval,
}
ADD_TO_DEVTABLE("x86cpu", x86_cpu_id, do_x86cpu_entry);
/* LOOKS like cpu:type:*:feature:*FEAT* */
static int do_cpu_entry(const char *filename, void *symval, char *alias)
{
DEF_FIELD(symval, cpu_feature, feature);
sprintf(alias, "cpu:type:*:feature:*%04X*", feature);
return 1;
}
ADD_TO_DEVTABLE("cpu", cpu_feature, do_cpu_entry);
/* Looks like: mei:S */
static int do_mei_entry(const char *filename, void *symval,
char *alias)