[PATCH v3 1/2] kernel: add platform_has() infrastructure

[Juergen Gross <jgross@xxxxxxxx>]

Add a simple infrastructure for setting, resetting and querying
platform feature flags.

Flags can be either global or architecture specific.

Signed-off-by: Juergen Gross <jgross@xxxxxxxx>
---
V2:
- rename set/reset functions to platform_[set|clear]() (Boris Petkov,
  Heiko Carstens)
- move function implementations to c file (Boris Petkov)
---
 MAINTAINERS                            |  8 ++++++++
 include/asm-generic/Kbuild             |  1 +
 include/asm-generic/platform-feature.h |  8 ++++++++
 include/linux/platform-feature.h       | 15 ++++++++++++++
 kernel/Makefile                        |  2 +-
 kernel/platform-feature.c              | 27 ++++++++++++++++++++++++++
 6 files changed, 60 insertions(+), 1 deletion(-)
 create mode 100644 include/asm-generic/platform-feature.h
 create mode 100644 include/linux/platform-feature.h
 create mode 100644 kernel/platform-feature.c

diff --git a/MAINTAINERS b/MAINTAINERS
index edc96cdb85e8..2749a88d75f2 100644
--- a/MAINTAINERS
+++ b/MAINTAINERS
@@ -15657,6 +15657,14 @@ S:     Maintained
 F:     Documentation/devicetree/bindings/iio/chemical/plantower,pms7003.yaml
 F:     drivers/iio/chemical/pms7003.c
 
+PLATFORM FEATURE INFRASTRUCTURE
+M:     Juergen Gross <jgross@xxxxxxxx>
+S:     Maintained
+F:     arch/*/include/asm/platform-feature.h
+F:     include/asm-generic/platform-feature.h
+F:     include/linux/platform-feature.h
+F:     kernel/platform-feature.c
+
 PLDMFW LIBRARY
 M:     Jacob Keller <jacob.e.keller@xxxxxxxxx>
 S:     Maintained
diff --git a/include/asm-generic/Kbuild b/include/asm-generic/Kbuild
index 302506bbc2a4..8e47d483b524 100644
--- a/include/asm-generic/Kbuild
+++ b/include/asm-generic/Kbuild
@@ -44,6 +44,7 @@ mandatory-y += msi.h
 mandatory-y += pci.h
 mandatory-y += percpu.h
 mandatory-y += pgalloc.h
+mandatory-y += platform-feature.h
 mandatory-y += preempt.h
 mandatory-y += rwonce.h
 mandatory-y += sections.h
diff --git a/include/asm-generic/platform-feature.h 
b/include/asm-generic/platform-feature.h
new file mode 100644
index 000000000000..4b0af3d51588
--- /dev/null
+++ b/include/asm-generic/platform-feature.h
@@ -0,0 +1,8 @@
+/* SPDX-License-Identifier: GPL-2.0 */
+#ifndef _ASM_GENERIC_PLATFORM_FEATURE_H
+#define _ASM_GENERIC_PLATFORM_FEATURE_H
+
+/* Number of arch specific feature flags. */
+#define PLATFORM_ARCH_FEAT_N   0
+
+#endif /* _ASM_GENERIC_PLATFORM_FEATURE_H */
diff --git a/include/linux/platform-feature.h b/include/linux/platform-feature.h
new file mode 100644
index 000000000000..6ed859928b97
--- /dev/null
+++ b/include/linux/platform-feature.h
@@ -0,0 +1,15 @@
+/* SPDX-License-Identifier: GPL-2.0 */
+#ifndef _PLATFORM_FEATURE_H
+#define _PLATFORM_FEATURE_H
+
+#include <linux/bitops.h>
+#include <asm/platform-feature.h>
+
+/* The platform features are starting with the architecture specific ones. */
+#define PLATFORM_FEAT_N                                (0 + 
PLATFORM_ARCH_FEAT_N)
+
+void platform_set(unsigned int feature);
+void platform_clear(unsigned int feature);
+bool platform_has(unsigned int feature);
+
+#endif /* _PLATFORM_FEATURE_H */
diff --git a/kernel/Makefile b/kernel/Makefile
index 847a82bfe0e3..2f412f80110d 100644
--- a/kernel/Makefile
+++ b/kernel/Makefile
@@ -7,7 +7,7 @@ obj-y     = fork.o exec_domain.o panic.o \
            cpu.o exit.o softirq.o resource.o \
            sysctl.o capability.o ptrace.o user.o \
            signal.o sys.o umh.o workqueue.o pid.o task_work.o \
-           extable.o params.o \
+           extable.o params.o platform-feature.o \
            kthread.o sys_ni.o nsproxy.o \
            notifier.o ksysfs.o cred.o reboot.o \
            async.o range.o smpboot.o ucount.o regset.o
diff --git a/kernel/platform-feature.c b/kernel/platform-feature.c
new file mode 100644
index 000000000000..cb6a6c3e4fed
--- /dev/null
+++ b/kernel/platform-feature.c
@@ -0,0 +1,27 @@
+// SPDX-License-Identifier: GPL-2.0
+
+#include <linux/bitops.h>
+#include <linux/cache.h>
+#include <linux/export.h>
+#include <linux/platform-feature.h>
+
+#define PLATFORM_FEAT_ARRAY_SZ  BITS_TO_LONGS(PLATFORM_FEAT_N)
+static unsigned long __read_mostly platform_features[PLATFORM_FEAT_ARRAY_SZ];
+
+void platform_set(unsigned int feature)
+{
+       set_bit(feature, platform_features);
+}
+EXPORT_SYMBOL_GPL(platform_set);
+
+void platform_clear(unsigned int feature)
+{
+       clear_bit(feature, platform_features);
+}
+EXPORT_SYMBOL_GPL(platform_clear);
+
+bool platform_has(unsigned int feature)
+{
+       return test_bit(feature, platform_features);
+}
+EXPORT_SYMBOL_GPL(platform_has);
-- 
2.35.3