[4/4] sample/reserved_mem: Introduce a sample of struct page and dio support to no-map rmem

diff --git a/samples/Kconfig b/samples/Kconfig
index b0503ef058d3..d83ba02ec215 100644
--- a/samples/Kconfig
+++ b/samples/Kconfig
@@ -6,6 +6,13 @@  menuconfig SAMPLES
 
 if SAMPLES
 
+config RESERVED_MEM_DIO
+	tristate "Build example reserved mem dio support"
+	depends on OF_RESERVED_MEM_DIO_SUPPORT
+	help
+	   Build kernel space sample module to show how to add struct
+		 page and dio support to reserved memory.
+
 config SAMPLE_AUXDISPLAY
 	bool "auxdisplay sample"
 	depends on CC_CAN_LINK
diff --git a/samples/Makefile b/samples/Makefile
index 087e0988ccc5..106a386869eb 100644
--- a/samples/Makefile
+++ b/samples/Makefile
@@ -1,6 +1,7 @@ 
 # SPDX-License-Identifier: GPL-2.0
 # Makefile for Linux samples code
 
+obj-$(CONFIG_RESERVED_MEM_DIO)		+= reserved_mem/
 subdir-$(CONFIG_SAMPLE_AUXDISPLAY)	+= auxdisplay
 subdir-$(CONFIG_SAMPLE_ANDROID_BINDERFS) += binderfs
 obj-$(CONFIG_SAMPLE_CONFIGFS)		+= configfs/
diff --git a/samples/reserved_mem/Makefile b/samples/reserved_mem/Makefile
new file mode 100755
index 000000000000..a4f5c8bc08dc
--- /dev/null
+++ b/samples/reserved_mem/Makefile
@@ -0,0 +1,2 @@ 
+# SPDX-License-Identifier: GPL-2.0-only
+obj-$(CONFIG_RESERVED_MEM_DIO) += rmem_dio.o
diff --git a/samples/reserved_mem/rmem_dio.c b/samples/reserved_mem/rmem_dio.c
new file mode 100755
index 000000000000..ffb3395de63c
--- /dev/null
+++ b/samples/reserved_mem/rmem_dio.c
@@ -0,0 +1,116 @@ 
+// SPDX-License-Identifier: GPL-2.0-only
+/*
+ * Sample driver for reserved memory with struct page and dio support.
+ *
+ * wsps is abbr for with struct page support
+ *
+ * Copyright (C) 2022 Li Chen <lchen@ambarella.com>
+ */
+
+#include <linux/module.h>
+#include <linux/init.h>
+#include <linux/kernel.h>
+#include <linux/fs.h>
+#include <linux/errno.h>
+#include <linux/types.h>
+#include <linux/mm.h>
+#include <linux/cdev.h>
+#include <linux/module.h>
+#include <linux/io.h>
+#include <linux/miscdevice.h>
+#include <linux/of_reserved_mem.h>
+#include <linux/platform_device.h>
+
+/*
+ * dts example
+ * rmem: rmem@1 {
+ *			compatible = "shared-dma-pool";
+ *			no-map;
+ *			size = <0x0 0x20000000>;
+ *		};
+ * perf {
+ *		compatible = "example,rmem";
+ *		memory-region = <&rmem>;
+ *	};
+ */
+
+static struct reserved_mem *rmem;
+
+static int rmem_wsps_open(struct inode *inode, struct file *filp)
+{
+	return 0;
+}
+
+static int rmem_wsps_release(struct inode *inode,
+					  struct file *filp)
+{
+	return 0;
+}
+
+static int rmem_wsps_mmap(struct file *file,
+					     struct vm_area_struct *vma)
+{
+	return reserved_mem_dio_mmap(file, vma, rmem);
+}
+
+static const struct file_operations rmem_wsps_remap_ops = {
+	.owner = THIS_MODULE,
+	.open = rmem_wsps_open,
+	.release = rmem_wsps_release,
+	.mmap = rmem_wsps_mmap,
+};
+
+static struct miscdevice rmem_wsps_miscdev = {
+	.minor = MISC_DYNAMIC_MINOR,
+	.name = "rmem_wsps",
+	.fops = &rmem_wsps_remap_ops,
+};
+
+static int rmem_wsps_probe(struct platform_device *pdev)
+{
+	struct device *dev = &pdev->dev;
+	void *vaddr;
+	int ret;
+
+	ret = misc_register(&rmem_wsps_miscdev);
+	if (ret) {
+		dev_err(dev, "%s: misc_register failed, %d\n", __func__, ret);
+		return -ENODEV;
+	}
+
+	rmem = get_reserved_mem_from_dev(dev);
+	if (!rmem) {
+		dev_err(dev, "%s: failed to find reserved\n", __func__);
+		return -ENODEV;
+	}
+
+	vaddr = reserved_mem_memremap_pages(dev, rmem);
+	if (IS_ERR_OR_NULL(vaddr))
+		return PTR_ERR(vaddr);
+
+	return 0;
+}
+
+static const struct of_device_id rmem_dio_match[] = {
+	{
+		.compatible = "example,rmem",
+	},
+	{ /* sentinel */ },
+};
+MODULE_DEVICE_TABLE(of, rmem_dio_match);
+
+static struct platform_driver rmem_wsps_driver = {
+	.probe = rmem_wsps_probe,
+	.driver = {
+		.name = "rmem_wsps",
+		.of_match_table = rmem_dio_match,
+	},
+};
+
+static int __init rmem_wsps_init(void)
+{
+	return platform_driver_register(&rmem_wsps_driver);
+}
+
+module_init(rmem_wsps_init);
+MODULE_LICENSE("GPL");