[RFC PATCH 7/7] x86/resctrl: Example resctrl driver

[Tony Luck <tony.luck@intel.com>]

Simply add two files to each ctrlmon directory that show the closid and
rmid respectively.

Signed-off-by: Tony Luck <tony.luck@intel.com>
---
 .../cpu/resctrl/drivers/resctrl_example.c     | 77 +++++++++++++++++++
 arch/x86/Kconfig                              | 11 +++
 arch/x86/kernel/cpu/resctrl/Makefile          |  1 +
 arch/x86/kernel/cpu/resctrl/drivers/Makefile  |  1 +
 4 files changed, 90 insertions(+)
 create mode 100644 arch/x86/kernel/cpu/resctrl/drivers/resctrl_example.c
 create mode 100644 arch/x86/kernel/cpu/resctrl/drivers/Makefile

diff --git a/arch/x86/kernel/cpu/resctrl/drivers/resctrl_example.c b/arch/x86/kernel/cpu/resctrl/drivers/resctrl_example.c
new file mode 100644
index 000000000000..24998e0dc3c2
--- /dev/null
+++ b/arch/x86/kernel/cpu/resctrl/drivers/resctrl_example.c
@@ -0,0 +1,77 @@
+// SPDX-License-Identifier: GPL-2.0-only
+/* Copyright(c) 2023 Intel Corporation. */
+
+/*
+ *  Example resctrl driver
+ */
+#include <linux/module.h>
+#include <linux/kernel.h>
+#include <linux/acpi.h>
+#include <linux/seq_file.h>
+#include <linux/slab.h>
+#include <linux/resctrl.h>
+
+#undef pr_fmt
+#define pr_fmt(fmt) "exampleresctrl: " fmt
+
+static int closid_show(struct seq_file *sf, void *arg)
+{
+	struct kernfs_open_file *of = sf->private;
+	unsigned long priv = (unsigned long)of->kn->priv;
+	u32 closid = priv >> 16;
+
+	seq_printf(sf, "%d\n", closid);
+
+	return 0;
+}
+
+static int rmid_show(struct seq_file *sf, void *arg)
+{
+	struct kernfs_open_file *of = sf->private;
+	unsigned long priv = (unsigned long)of->kn->priv;
+	u32 rmid = priv & 0xffff;
+
+	seq_printf(sf, "%d\n", rmid);
+
+	return 0;
+}
+
+static struct kernfs_ops closid_ops = {
+	.seq_show	= closid_show,
+};
+
+static struct kernfs_ops rmid_ops = {
+	.seq_show	= rmid_show,
+};
+
+static struct resctrl_fileinfo files[] = {
+	{
+		.name = "closid", .ops = &closid_ops
+	},
+	{
+		.name = "rmid", .ops = &rmid_ops
+	},
+	{
+	}
+};
+
+static struct resctrl_driver ops = {
+	.ctrlfiles	= files,
+};
+
+static int __init init_example(void)
+{
+	resctrl_register_driver(&ops);
+
+	return 0;
+}
+
+static void __exit cleanup_example(void)
+{
+	resctrl_unregister_driver(&ops);
+}
+
+module_init(init_example);
+module_exit(cleanup_example);
+
+MODULE_LICENSE("GPL");
diff --git a/arch/x86/Kconfig b/arch/x86/Kconfig
index a825bf031f49..7f2faec17365 100644
--- a/arch/x86/Kconfig
+++ b/arch/x86/Kconfig
@@ -500,6 +500,17 @@ config X86_CPU_RESCTRL
 
 	  Say N if unsure.
 
+config X86_CPU_RESCTRL_DRIVERS
+	bool "resctrl driver"
+
+config X86_CPU_RESCTRL_EXAMPLE_DRIVER
+	tristate "example x86 resctrl driver"
+	depends on X86_CPU_RESCTRL
+	select X86_CPU_RESCTRL_DRIVERS
+	help
+	  Example driver to show one possible use case for
+	  resctrl driver registration.
+
 if X86_32
 config X86_BIGSMP
 	bool "Support for big SMP systems with more than 8 CPUs"
diff --git a/arch/x86/kernel/cpu/resctrl/Makefile b/arch/x86/kernel/cpu/resctrl/Makefile
index 4a06c37b9cf1..7db4d729afbc 100644
--- a/arch/x86/kernel/cpu/resctrl/Makefile
+++ b/arch/x86/kernel/cpu/resctrl/Makefile
@@ -1,4 +1,5 @@
 # SPDX-License-Identifier: GPL-2.0
 obj-$(CONFIG_X86_CPU_RESCTRL)	+= core.o rdtgroup.o monitor.o
 obj-$(CONFIG_X86_CPU_RESCTRL)	+= ctrlmondata.o pseudo_lock.o
+obj-$(CONFIG_X86_CPU_RESCTRL_DRIVERS) += drivers/
 CFLAGS_pseudo_lock.o = -I$(src)
diff --git a/arch/x86/kernel/cpu/resctrl/drivers/Makefile b/arch/x86/kernel/cpu/resctrl/drivers/Makefile
new file mode 100644
index 000000000000..27db936eb947
--- /dev/null
+++ b/arch/x86/kernel/cpu/resctrl/drivers/Makefile
@@ -0,0 +1 @@
+obj-$(CONFIG_X86_CPU_RESCTRL_EXAMPLE_DRIVER) += resctrl_example.o
-- 
2.39.2