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

From: Juergen Gross via Virtualization <virtualization@lists.linux-foundation.org>
To: linux-kernel@vger.kernel.org, x86@kernel.org,
	linux-arch@vger.kernel.org, linux-s390@vger.kernel.org,
	linux-hyperv@vger.kernel.org,
	virtualization@lists.linux-foundation.org
Cc: "Michael S. Tsirkin" <mst@redhat.com>,
	Peter Zijlstra <peterz@infradead.org>,
	Dave Hansen <dave.hansen@linux.intel.com>,
	"H. Peter Anvin" <hpa@zytor.com>,
	Alexander Gordeev <agordeev@linux.ibm.com>,
	Wei Liu <wei.liu@kernel.org>,
	Stephen Hemminger <sthemmin@microsoft.com>,
	Vasily Gorbik <gor@linux.ibm.com>,
	Dexuan Cui <decui@microsoft.com>,
	Christoph Hellwig <hch@infradead.org>,
	Ingo Molnar <mingo@redhat.com>,
	Haiyang Zhang <haiyangz@microsoft.com>,
	Arnd Bergmann <arnd@arndb.de>, Heiko Carstens <hca@linux.ibm.com>,
	Borislav Petkov <bp@alien8.de>, Andy Lutomirski <luto@kernel.org>,
	Thomas Gleixner <tglx@linutronix.de>,
	Juergen Gross <jgross@suse.com>,
	Oleksandr Tyshchenko <olekstysh@gmail.com>,
	Sven Schnelle <svens@linux.ibm.com>
Subject: [PATCH 1/2] kernel: add platform_has() infrastructure
Date: Tue, 26 Apr 2022 15:40:20 +0200	[thread overview]
Message-ID: <20220426134021.11210-2-jgross@suse.com> (raw)
In-Reply-To: <20220426134021.11210-1-jgross@suse.com>

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@suse.com>
---
 MAINTAINERS                            |  8 +++++++
 include/asm-generic/Kbuild             |  1 +
 include/asm-generic/platform-feature.h |  8 +++++++
 include/linux/platform-feature.h       | 29 ++++++++++++++++++++++++++
 kernel/Makefile                        |  2 +-
 kernel/platform-feature.c              |  7 +++++++
 6 files changed, 54 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 5e8c2f611766..eb943f089eda 100644
--- a/MAINTAINERS
+++ b/MAINTAINERS
@@ -15650,6 +15650,14 @@ S:	Maintained
 F:	Documentation/devicetree/bindings/iio/chemical/plantower,pms7003.yaml
 F:	drivers/iio/chemical/pms7003.c
 
+PLATFORM FEATURE INFRASTRUCTURE
+M:	Juergen Gross <jgross@suse.com>
+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@intel.com>
 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..df393d502a4f
--- /dev/null
+++ b/include/linux/platform-feature.h
@@ -0,0 +1,29 @@
+/* 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)
+
+#define PLATFORM_FEAT_ARRAY_SZ	BITS_TO_LONGS(PLATFORM_FEAT_N)
+extern unsigned long platform_features[PLATFORM_FEAT_ARRAY_SZ];
+
+static inline void platform_set_feature(unsigned int feature)
+{
+	set_bit(feature, platform_features);
+}
+
+static inline void platform_reset_feature(unsigned int feature)
+{
+	clear_bit(feature, platform_features);
+}
+
+static inline bool platform_has(unsigned int feature)
+{
+	return test_bit(feature, platform_features);
+}
+
+#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..2d52f8442cd5
--- /dev/null
+++ b/kernel/platform-feature.c
@@ -0,0 +1,7 @@
+// SPDX-License-Identifier: GPL-2.0
+
+#include <linux/cache.h>
+#include <linux/platform-feature.h>
+
+unsigned long __read_mostly platform_features[PLATFORM_FEAT_ARRAY_SZ];
+EXPORT_SYMBOL_GPL(platform_features);
-- 
2.34.1

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