Add a runtime interface to using configfs for generic device tree overlay
usage. With it its possible to use device tree overlays without having
to use a per-platform overlay manager.
Please see Documentation/devicetree/configfs-overlays.txt for more info.
Changes since v2:
- Removed ifdef CONFIG_OF_OVERLAY (since for now it's required)
- Created a documentation entry
- Slight rewording in Kconfig
Changes since v1:
- of_resolve() -> of_resolve_phandles().
Signed-off-by: Pantelis Antoniou <pantelis.antoniou@xxxxxxxxxxxx>
---
Documentation/devicetree/configfs-overlays.txt | 31 +++
drivers/of/Kconfig | 7 +
drivers/of/Makefile | 1 +
drivers/of/configfs.c | 332 +++++++++++++++++++++++++
4 files changed, 371 insertions(+)
create mode 100644 Documentation/devicetree/configfs-overlays.txt
create mode 100644 drivers/of/configfs.c
diff --git a/Documentation/devicetree/configfs-overlays.txt b/Documentation/devicetree/configfs-overlays.txt
new file mode 100644
index 0000000..5fa43e0
--- /dev/null
+++ b/Documentation/devicetree/configfs-overlays.txt
@@ -0,0 +1,31 @@
+Howto use the configfs overlay interface.
+
+A device-tree configfs entry is created in /config/device-tree/overlays
+and and it is manipulated using standard file system I/O.
+Note that this is a debug level interface, for use by developers and
+not necessarily something accessed by normal users due to the
+security implications of having direct access to the kernel's device tree.
+
+* To create an overlay you mkdir the directory:
+
+ # mkdir /config/device-tree/overlays/foo
+
+* Either you echo the overlay firmware file to the path property file.
+
+ # echo foo.dtbo >/config/device-tree/overlays/foo/path
+
+* Or you cat the contents of the overlay to the dtbo file
+
+ # cat foo.dtbo >/config/device-tree/overlays/foo/dtbo
+
+The overlay file will be applied, and devices will be created/destroyed
+as required.
+
+To remove it simply rmdir the directory.
+
+ # rmdir /config/device-tree/overlays/foo
+
+The rationalle of the dual interface (firmware & direct copy) is that each is
+better suited to different use patterns. The firmware interface is what's
+intended to be used by hardware managers in the kernel, while the copy interface
+make sense for developers (since it avoids problems with namespaces).
diff --git a/drivers/of/Kconfig b/drivers/of/Kconfig
index 18b2e25..5d36306 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 "Device Tree Overlay ConfigFS interface"
+ select CONFIGFS_FS
+ select OF_OVERLAY
+ help
+ Enable a simple user-space driven DT overlay interface.
+
endmenu # OF
diff --git a/drivers/of/Makefile b/drivers/of/Makefile
index 7563f36..6f7f4f8 100644
--- a/drivers/of/Makefile
+++ b/drivers/of/Makefile
@@ -1,4 +1,5 @@
obj-y = base.o device.o platform.o
+obj-$(CONFIG_OF_CONFIGFS) += configfs.o
obj-$(CONFIG_OF_DYNAMIC) += dynamic.o
obj-$(CONFIG_OF_FLATTREE) += fdt.o
obj-$(CONFIG_OF_EARLY_FLATTREE) += fdt_address.o
diff --git a/drivers/of/configfs.c b/drivers/of/configfs.c
new file mode 100644
index 0000000..1434ade
--- /dev/null
+++ b/drivers/of/configfs.c
@@ -0,0 +1,332 @@
+/*
+ * 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"
+
+struct cfs_overlay_item {
+ struct config_item item;
+
+ char path[PATH_MAX];
+
+ const struct firmware *fw;
+ struct device_node *overlay;
+ int ov_id;
+
+ void *dtbo;
+ int dtbo_size;
+};
+
+static int create_overlay(struct cfs_overlay_item *overlay, void *blob)
+{
+ int err;
+
+ /* unflatten the tree */
+ of_fdt_unflatten_tree(blob, &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_phandles(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;
+
+out_err:
+ return err;
+}
+
+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)
+
+CONFIGFS_BIN_ATTR_STRUCT(cfs_overlay_item);
+#define CFS_OVERLAY_ITEM_BIN_ATTR(_name, _mode, _read, _write, _priv, _max) \
+struct cfs_overlay_item_bin_attribute cfs_overlay_item_bin_attr_##_name = \
+ __CONFIGFS_BIN_ATTR(_name, _mode, _read, _write, _priv, _max)
+#define CFS_OVERLAY_ITEM_BIN_ATTR_RO(_name, _read, _priv, _max) \
+struct cfs_overlay_item_bin_attribute cfs_overlay_item_bin_attr_##_name = \
+ __CONFIGFS_BIN_ATTR_RO(_name, _read, _priv, _max)
+
+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' || overlay->dtbo_size > 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;
+
+ err = create_overlay(overlay, (void *)overlay->fw->data);
+ if (err != 0)
+ goto out_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,
+};
+
+ssize_t cfs_overlay_item_dtbo_read(struct cfs_overlay_item *overlay,
+ void *buf, size_t max_count)
+{
+ pr_debug("%s: buf=%p max_count=%u\n", __func__,
+ buf, max_count);
+
+ if (overlay->dtbo == NULL)
+ return 0;
+
+ /* copy if buffer provided */
+ if (buf != NULL) {
+ /* the buffer must be large enough */
+ if (overlay->dtbo_size > max_count)
+ return -ENOSPC;
+
+ memcpy(buf, overlay->dtbo, overlay->dtbo_size);
+ }
+
+ return overlay->dtbo_size;
+}
+
+ssize_t cfs_overlay_item_dtbo_write(struct cfs_overlay_item *overlay,
+ const void *buf, size_t count)
+{
+ int err;
+
+ /* if it's set do not allow changes */
+ if (overlay->path[0] != '\0' || overlay->dtbo_size > 0)
+ return -EPERM;
+
+ /* copy the contents */
+ overlay->dtbo = kmemdup(buf, count, GFP_KERNEL);
+ if (overlay->dtbo == NULL)
+ return -ENOMEM;
+
+ overlay->dtbo_size = count;
+
+ err = create_overlay(overlay, overlay->dtbo);
+ if (err != 0)
+ goto out_err;
+
+ return count;
+
+out_err:
+ kfree(overlay->dtbo);
+ overlay->dtbo = NULL;
+ overlay->dtbo_size = 0;
+
+ return err;
+}
+
+CFS_OVERLAY_ITEM_BIN_ATTR(dtbo, S_IRUGO | S_IWUSR,
+ cfs_overlay_item_dtbo_read, cfs_overlay_item_dtbo_write,
+ NULL, SZ_1M);
+
+static struct configfs_bin_attribute *cfs_overlay_bin_attrs[] = {
+ &cfs_overlay_item_bin_attr_dtbo.bin_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 with NULL is safe */
+ kfree(overlay->dtbo);
+ kfree(overlay);
+}
+
+CONFIGFS_ATTR_OPS(cfs_overlay_item);
+CONFIGFS_BIN_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,
+ .read_bin_attribute = cfs_overlay_item_bin_attr_read,
+ .write_bin_attribute = cfs_overlay_item_bin_attr_write,
+};
+
+static struct config_item_type cfs_overlay_type = {
+ .ct_item_ops = &cfs_overlay_item_ops,
+ .ct_attrs = cfs_overlay_attrs,
+ .ct_bin_attrs = cfs_overlay_bin_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,
+};
+
+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[] = {
+ &of_cfs_overlay_group,
+ 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);
+ config_group_init_type_name(&of_cfs_overlay_group, "overlays",
+ &overlays_type);
+
+ 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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