Initial commit

package/kernel/ubootenv-nvram/Makefile

@@ -0,0 +1,30 @@
+include $(TOPDIR)/rules.mk
+include $(INCLUDE_DIR)/kernel.mk
+
+PKG_NAME:=ubootenv-nvram
+PKG_RELEASE:=1
+PKG_LICENSE:=GPL-2.0
+
+include $(INCLUDE_DIR)/package.mk
+
+define KernelPackage/ubootenv-nvram
+  SUBMENU:=Other modules
+  TITLE:=NVRAM environment for uboot-envtools
+  FILES:=$(PKG_BUILD_DIR)/ubootenv-nvram.ko
+  AUTOLOAD:=$(call AutoLoad,30,ubootenv-nvram,1)
+  KCONFIG:=
+endef
+
+define KernelPackage/ubootenv-nvram/description
+  Support vendor modified U-Boot storing the environment
+  in RAM.  This driver exports the environment memory
+  region as a misc device named "ubootenv", pretending
+  it is a NOR mtd device to let existing userspace tools
+  work without modifications.
+endef
+
+define Build/Compile
+	$(KERNEL_MAKE) M="$(PKG_BUILD_DIR)" modules
+endef
+
+$(eval $(call KernelPackage,ubootenv-nvram))

package/kernel/ubootenv-nvram/src/Makefile

@@ -0,0 +1 @@
+obj-m += ubootenv-nvram.o

package/kernel/ubootenv-nvram/src/ubootenv-nvram.c

@@ -0,0 +1,158 @@
+// SPDX-License-Identifier: GPL-2.0-only
+/*
+ *   Copyright (C) 2022  Bjørn Mork <bjorn@mork.no>
+ */
+
+#include <linux/fs.h>
+#include <linux/init.h>
+#include <linux/io.h>
+#include <linux/miscdevice.h>
+#include <linux/mm.h>
+#include <linux/module.h>
+#include <linux/mtd/mtd.h>
+#include <linux/of.h>
+#include <linux/of_reserved_mem.h>
+#include <linux/platform_device.h>
+
+#define NAME "ubootenv"
+
+struct ubootenv_drvdata {
+	void *env;
+	struct reserved_mem *rmem;
+	struct miscdevice misc;
+};
+
+static inline struct ubootenv_drvdata *to_ubootenv_drvdata(struct file *file)
+{
+	return container_of(file->private_data, struct ubootenv_drvdata, misc);
+}
+
+static ssize_t ubootenv_write(struct file *file, const char __user *buffer, size_t count,
+			      loff_t *ppos)
+{
+	struct ubootenv_drvdata *data = to_ubootenv_drvdata(file);
+
+	if (!data->env)
+		return -EIO;
+	return simple_write_to_buffer(data->env, data->rmem->size, ppos, buffer, count);
+}
+
+static ssize_t ubootenv_read(struct file *file, char __user *buffer, size_t count, loff_t *ppos)
+{
+	struct ubootenv_drvdata *data = to_ubootenv_drvdata(file);
+
+	if (!data->env)
+		return 0;
+	return simple_read_from_buffer(buffer, count, ppos, data->env, data->rmem->size);
+}
+
+static loff_t ubootenv_llseek(struct file *file, loff_t off, int whence)
+{
+	struct ubootenv_drvdata *data = to_ubootenv_drvdata(file);
+
+	return fixed_size_llseek(file, off, whence, data->rmem->size);
+}
+
+/* Faking the minimal mtd ioctl subset required by the fw_env.c */
+static long ubootenv_ioctl(struct file *file, u_int cmd, u_long arg)
+{
+	struct ubootenv_drvdata *data = to_ubootenv_drvdata(file);
+	void __user *argp = (void __user *)arg;
+	struct mtd_info_user info = {
+		.type = MTD_NORFLASH,
+		.size = data->rmem->size,
+	};
+
+	switch (cmd) {
+	case MEMISLOCKED:
+	case MEMERASE:
+		break;
+	case MEMGETINFO:
+		if (copy_to_user(argp, &info, sizeof(struct mtd_info_user)))
+			return -EFAULT;
+		break;
+	default:
+		return -ENOTTY;
+	}
+	return 0;
+}
+
+static const struct file_operations ubootenv_fops = {
+	.owner          = THIS_MODULE,
+	.read           = ubootenv_read,
+	.write          = ubootenv_write,
+	.llseek         = ubootenv_llseek,
+	.unlocked_ioctl = ubootenv_ioctl,
+};
+
+/* We can only map a single reserved-memory range */
+static struct ubootenv_drvdata drvdata = {
+	.misc = {
+		.fops  = &ubootenv_fops,
+		.minor = MISC_DYNAMIC_MINOR,
+		.name  = NAME,
+	},
+};
+
+const struct of_device_id of_ubootenv_match[] = {
+	{ .compatible = "ubootenv" },
+	{},
+};
+MODULE_DEVICE_TABLE(of, of_ubootenv_match);
+
+static int ubootenv_probe(struct platform_device *pdev)
+{
+	struct ubootenv_drvdata *data = &drvdata;
+	struct device *dev = &pdev->dev;
+	struct device_node *np;
+
+	/* enforce single instance */
+	if (data->env)
+		return -EINVAL;
+
+	np = of_parse_phandle(dev->of_node, "memory-region", 0);
+	if (!np)
+		return -ENODEV;
+
+	data->rmem = of_reserved_mem_lookup(np);
+	of_node_put(np);
+	if (!data->rmem)
+		return -ENODEV;
+
+	if (!data->rmem->size || (data->rmem->size > ULONG_MAX))
+		return -EINVAL;
+
+	if (!PAGE_ALIGNED(data->rmem->base) || !PAGE_ALIGNED(data->rmem->size))
+		return -EINVAL;
+
+	data->env = devm_memremap(&pdev->dev, data->rmem->base, data->rmem->size, MEMREMAP_WB);
+	platform_set_drvdata(pdev, data);
+
+	data->misc.parent = &pdev->dev;
+	return misc_register(&data->misc);
+}
+
+static int ubootenv_remove(struct platform_device *pdev)
+{
+	struct ubootenv_drvdata *data = platform_get_drvdata(pdev);
+
+	data->env = NULL;
+	misc_deregister(&data->misc);
+	return 0;
+}
+
+static struct platform_driver ubootenv_driver = {
+	.probe = ubootenv_probe,
+	.remove = ubootenv_remove,
+	.driver = {
+		.name           = NAME,
+		.owner          = THIS_MODULE,
+		.of_match_table = of_ubootenv_match,
+	},
+};
+
+module_platform_driver(ubootenv_driver);
+
+MODULE_LICENSE("GPL");
+MODULE_AUTHOR("Bjørn Mork <bjorn@mork.no>");
+MODULE_DESCRIPTION("Access u-boot environment in RAM");