[PATCH v5 3/9] OF: DT-Overlay configfs interface

[Pantelis Antoniou]

Add a runtime interface to using configfs for generic device tree overlay
usage.

A device-tree configfs entry is created in /config/device-tree/overlays

To create an overlay you mkdir the directory and then echo the overlay
firmware file to the path property file.

	# mkdir /config/device-tree/overlays/foo
	# echo foo.dtbo >/config/device-tree/overlays/foo/path

The overlay file will be loaded using the standard firmware loader
and will be applied.

To remove it simply rmdir the directory.

	# rmdir /config/device-tree/overlays/foo

Signed-off-by: Pantelis Antoniou <pantelis.antoniou@xxxxxxxxxxxx>
---
 drivers/of/Kconfig    |   7 ++
 drivers/of/Makefile   |   1 +
 drivers/of/configfs.c | 251 ++++++++++++++++++++++++++++++++++++++++++++++++++
 3 files changed, 259 insertions(+)
 create mode 100644 drivers/of/configfs.c

diff --git a/drivers/of/Kconfig b/drivers/of/Kconfig
index 5ebde98..1a2ff48 100644
--- a/drivers/of/Kconfig
+++ b/drivers/of/Kconfig
@@ -91,4 +91,11 @@ config OF_OVERLAY
 	select OF_DEVICE
 	select OF_RESOLVE
 
+config OF_CONFIGFS
+	bool "OpenFirmware Overlay ConfigFS interface"
+	select CONFIGFS_FS
+	select OF_OVERLAY
+	help
+	  Enable a simple user-space driver DT overlay interface.
+
 endmenu # OF
diff --git a/drivers/of/Makefile b/drivers/of/Makefile
index e1f864a..46b3308 100644
--- a/drivers/of/Makefile
+++ b/drivers/of/Makefile
@@ -12,5 +12,6 @@ obj-$(CONFIG_OF_MTD)	+= of_mtd.o
 obj-$(CONFIG_OF_RESERVED_MEM) += of_reserved_mem.o
 obj-$(CONFIG_OF_RESOLVE)  += resolver.o
 obj-$(CONFIG_OF_OVERLAY) += overlay.o
+obj-$(CONFIG_OF_CONFIGFS) += configfs.o
 
 CFLAGS_fdt.o = -I$(src)/../../scripts/dtc/libfdt
diff --git a/drivers/of/configfs.c b/drivers/of/configfs.c
new file mode 100644
index 0000000..2f5584f
--- /dev/null
+++ b/drivers/of/configfs.c
@@ -0,0 +1,251 @@
+/*
+ * Configfs entries for device-tree
+ *
+ * Copyright (C) 2013 - Pantelis Antoniou <panto@xxxxxxxxxxxxxxxxxxxxxxx>
+ *
+ * This program is free software; you can redistribute it and/or
+ * modify it under the terms of the GNU General Public License
+ * as published by the Free Software Foundation; either version
+ * 2 of the License, or (at your option) any later version.
+ */
+#include <linux/ctype.h>
+#include <linux/cpu.h>
+#include <linux/module.h>
+#include <linux/of.h>
+#include <linux/of_fdt.h>
+#include <linux/spinlock.h>
+#include <linux/slab.h>
+#include <linux/proc_fs.h>
+#include <linux/configfs.h>
+#include <linux/types.h>
+#include <linux/stat.h>
+#include <linux/limits.h>
+#include <linux/file.h>
+#include <linux/vmalloc.h>
+#include <linux/firmware.h>
+
+#include "of_private.h"
+
+#ifdef CONFIG_OF_OVERLAY
+
+struct cfs_overlay_item {
+	struct config_item	item;
+
+	char			path[PATH_MAX];
+
+	const struct firmware	*fw;
+	struct device_node	*overlay;
+	int			ov_id;
+};
+
+static inline struct cfs_overlay_item *to_cfs_overlay_item(
+		struct config_item *item)
+{
+	return item ? container_of(item, struct cfs_overlay_item, item) : NULL;
+}
+
+CONFIGFS_ATTR_STRUCT(cfs_overlay_item);
+#define CFS_OVERLAY_ITEM_ATTR(_name, _mode, _show, _store)	\
+struct cfs_overlay_item_attribute cfs_overlay_item_attr_##_name = \
+	__CONFIGFS_ATTR(_name, _mode, _show, _store)
+#define CFS_OVERLAY_ITEM_ATTR_RO(_name, _show)	\
+struct cfs_overlay_item_attribute cfs_overlay_item_attr_##_name = \
+	__CONFIGFS_ATTR_RO(_name, _show)
+
+static ssize_t cfs_overlay_item_path_show(struct cfs_overlay_item *overlay,
+		char *page)
+{
+	return sprintf(page, "%s\n", overlay->path);
+}
+
+static ssize_t cfs_overlay_item_path_store(struct cfs_overlay_item *overlay,
+		const char *page, size_t count)
+{
+	const char *p = page;
+	char *s;
+	int err;
+
+	/* if it's set do not allow changes */
+	if (overlay->path[0] != '\0')
+		return -EPERM;
+
+	/* copy to path buffer (and make sure it's always zero terminated */
+	count = snprintf(overlay->path, sizeof(overlay->path) - 1, "%s", p);
+	overlay->path[sizeof(overlay->path) - 1] = '\0';
+
+	/* strip trailing newlines */
+	s = overlay->path + strlen(overlay->path);
+	while (s > overlay->path && *--s == '\n')
+		*s = '\0';
+
+	pr_debug("%s: path is '%s'\n", __func__, overlay->path);
+
+	err = request_firmware(&overlay->fw, overlay->path, NULL);
+	if (err != 0)
+		goto out_err;
+
+	/* unflatten the tree */
+	of_fdt_unflatten_tree((void *)overlay->fw->data, &overlay->overlay);
+	if (overlay->overlay == NULL) {
+		pr_err("%s: failed to unflatten tree\n", __func__);
+		err = -EINVAL;
+		goto out_err;
+	}
+	pr_debug("%s: unflattened OK\n", __func__);
+
+	/* mark it as detached */
+	of_node_set_flag(overlay->overlay, OF_DETACHED);
+
+	/* perform resolution */
+	err = of_resolve(overlay->overlay);
+	if (err != 0) {
+		pr_err("%s: Failed to resolve tree\n", __func__);
+		goto out_err;
+	}
+	pr_debug("%s: resolved OK\n", __func__);
+
+	err = of_overlay_create(overlay->overlay);
+	if (err < 0) {
+		pr_err("%s: Failed to create overlay (err=%d)\n",
+				__func__, err);
+		goto out_err;
+	}
+	overlay->ov_id = err;
+
+	return count;
+
+out_err:
+
+	release_firmware(overlay->fw);
+	overlay->fw = NULL;
+
+	overlay->path[0] = '\0';
+	return err;
+}
+
+static ssize_t cfs_overlay_item_status_show(struct cfs_overlay_item *overlay,
+		char *page)
+{
+	return sprintf(page, "%s\n",
+			overlay->ov_id >= 0 ? "applied" : "unapplied");
+}
+
+CFS_OVERLAY_ITEM_ATTR(path, S_IRUGO | S_IWUSR,
+		cfs_overlay_item_path_show, cfs_overlay_item_path_store);
+CFS_OVERLAY_ITEM_ATTR_RO(status, cfs_overlay_item_status_show);
+
+static struct configfs_attribute *cfs_overlay_attrs[] = {
+	&cfs_overlay_item_attr_path.attr,
+	&cfs_overlay_item_attr_status.attr,
+	NULL,
+};
+
+static void cfs_overlay_release(struct config_item *item)
+{
+	struct cfs_overlay_item *overlay = to_cfs_overlay_item(item);
+
+	if (overlay->ov_id >= 0)
+		of_overlay_destroy(overlay->ov_id);
+	if (overlay->fw)
+		release_firmware(overlay->fw);
+	kfree(overlay);
+}
+
+CONFIGFS_ATTR_OPS(cfs_overlay_item);
+static struct configfs_item_operations cfs_overlay_item_ops = {
+	.release		= cfs_overlay_release,
+	.show_attribute		= cfs_overlay_item_attr_show,
+	.store_attribute	= cfs_overlay_item_attr_store,
+};
+
+static struct config_item_type cfs_overlay_type = {
+	.ct_item_ops	= &cfs_overlay_item_ops,
+	.ct_attrs	= cfs_overlay_attrs,
+	.ct_owner	= THIS_MODULE,
+};
+
+static struct config_item *cfs_overlay_group_make_item(
+		struct config_group *group, const char *name)
+{
+	struct cfs_overlay_item *overlay;
+
+	overlay = kzalloc(sizeof(*overlay), GFP_KERNEL);
+	if (!overlay)
+		return ERR_PTR(-ENOMEM);
+	overlay->ov_id = -1;
+
+	config_item_init_type_name(&overlay->item, name, &cfs_overlay_type);
+	return &overlay->item;
+}
+
+static void cfs_overlay_group_drop_item(struct config_group *group,
+		struct config_item *item)
+{
+	struct cfs_overlay_item *overlay = to_cfs_overlay_item(item);
+
+	config_item_put(&overlay->item);
+}
+
+static struct configfs_group_operations overlays_ops = {
+	.make_item	= cfs_overlay_group_make_item,
+	.drop_item	= cfs_overlay_group_drop_item,
+};
+
+static struct config_item_type overlays_type = {
+	.ct_group_ops   = &overlays_ops,
+	.ct_owner       = THIS_MODULE,
+};
+
+#endif /* CONFIG_OF_OVERLAY */
+
+static struct configfs_group_operations of_cfs_ops = {
+	/* empty - we don't allow anything to be created */
+};
+
+static struct config_item_type of_cfs_type = {
+	.ct_group_ops   = &of_cfs_ops,
+	.ct_owner       = THIS_MODULE,
+};
+
+struct config_group of_cfs_overlay_group;
+
+struct config_group *of_cfs_def_groups[] = {
+#ifdef CONFIG_OF_OVERLAY
+	&of_cfs_overlay_group,
+#endif
+	NULL
+};
+
+static struct configfs_subsystem of_cfs_subsys = {
+	.su_group = {
+		.cg_item = {
+			.ci_namebuf = "device-tree",
+			.ci_type = &of_cfs_type,
+		},
+		.default_groups = of_cfs_def_groups,
+	},
+	.su_mutex = __MUTEX_INITIALIZER(of_cfs_subsys.su_mutex),
+};
+
+static int __init of_cfs_init(void)
+{
+	int ret;
+
+	pr_info("%s\n", __func__);
+
+	config_group_init(&of_cfs_subsys.su_group);
+#ifdef CONFIG_OF_OVERLAY
+	config_group_init_type_name(&of_cfs_overlay_group, "overlays",
+			&overlays_type);
+#endif
+
+	ret = configfs_register_subsystem(&of_cfs_subsys);
+	if (ret != 0) {
+		pr_err("%s: failed to register subsys\n", __func__);
+		goto out;
+	}
+	pr_info("%s: OK\n", __func__);
+out:
+	return ret;
+}
+late_initcall(of_cfs_init);
-- 
1.7.12

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