diff mbox series

[1/6] kernel: import dt-overlay configfs patches for 5.10

Message ID YZ7hf0DVfM7LSobG@makrotopia.org
State Under Review
Delegated to: Daniel Golle
Headers show
Series [1/6] kernel: import dt-overlay configfs patches for 5.10 | expand

Commit Message

Daniel Golle Nov. 25, 2021, 1:06 a.m. UTC
Import patchset allowing loading and applying device tree overlays at
run-time via configfs.

This will allow for packaging DTOs for hardware add-ons such as the
various HATs (Hardware Attached on Top) common for SBCs.
A new kernel config option CONFIG_OF_CONFIGFS is introduced and some
additional sysfs attributes are added in case CONFIG_OF_OVERLAY is
enabled.

To make use of this feature, both CONFIG_OF_CONFIGFS and
CONFIG_OF_OVERLAY need to be enabled in a targets kernel config.
This is currently already the case for mediatek/mt7622 and
mediatek/mt7623 as it has already been enabled by commit 401d7ebf2c
("mediatek: enable configfs for DT overlay on mt7622 and mt7623").

Signed-off-by: Daniel Golle <daniel@makrotopia.org>
---
 target/linux/generic/config-5.10              |   1 +
 .../hack-5.10/230-openwrt_lzma_options.patch  |   2 +-
 ...-OF-DT-Overlay-configfs-interface-v7.patch | 395 ++++++++++++++++++
 ...f-overlay-kobjectify-overlay-objects.patch | 157 +++++++
 ...verlay-global-sysfs-enable-attribute.patch | 105 +++++
 ...ation-ABI-overlays-global-attributes.patch |  40 ++
 ...ocument-of_overlay_disable-parameter.patch |  23 +
 ...lay-add-per-overlay-sysfs-attributes.patch | 243 +++++++++++
 ...tation-ABI-overlays-per-overlay-docs.patch |  46 ++
 ...-of-rename-_node_sysfs-to-_node_post.patch | 150 +++++++
 ...-symbols-when-CONFIG_OF_OVERLAY-is-u.patch |  27 ++
 11 files changed, 1188 insertions(+), 1 deletion(-)
 create mode 100644 target/linux/generic/pending-5.10/060-OF-DT-Overlay-configfs-interface-v7.patch
 create mode 100644 target/linux/generic/pending-5.10/061-of-overlay-kobjectify-overlay-objects.patch
 create mode 100644 target/linux/generic/pending-5.10/062-of-overlay-global-sysfs-enable-attribute.patch
 create mode 100644 target/linux/generic/pending-5.10/063-Documentation-ABI-overlays-global-attributes.patch
 create mode 100644 target/linux/generic/pending-5.10/064-Documentation-document-of_overlay_disable-parameter.patch
 create mode 100644 target/linux/generic/pending-5.10/065-of-overlay-add-per-overlay-sysfs-attributes.patch
 create mode 100644 target/linux/generic/pending-5.10/066-Documentation-ABI-overlays-per-overlay-docs.patch
 create mode 100644 target/linux/generic/pending-5.10/067-of-rename-_node_sysfs-to-_node_post.patch
 create mode 100644 target/linux/generic/pending-5.10/068-kbuild-Enable-DT-symbols-when-CONFIG_OF_OVERLAY-is-u.patch

Comments

Oskari Lemmelä Nov. 27, 2021, 9:28 a.m. UTC | #1
Hi,

On 25.11.2021 3.06, Daniel Golle wrote:
> Import patchset allowing loading and applying device tree overlays at
> run-time via configfs.
> 
> This will allow for packaging DTOs for hardware add-ons such as the
> various HATs (Hardware Attached on Top) common for SBCs.
> A new kernel config option CONFIG_OF_CONFIGFS is introduced and some
> additional sysfs attributes are added in case CONFIG_OF_OVERLAY is
> enabled.

Is this something that did not get accepted by upstream linux?
Those patches seem to be almost 8 years old.

> 
> To make use of this feature, both CONFIG_OF_CONFIGFS and
> CONFIG_OF_OVERLAY need to be enabled in a targets kernel config.
> This is currently already the case for mediatek/mt7622 and
> mediatek/mt7623 as it has already been enabled by commit 401d7ebf2c
> ("mediatek: enable configfs for DT overlay on mt7622 and mt7623").
> 
> Signed-off-by: Daniel Golle <daniel@makrotopia.org>

Oskari
Daniel Golle Nov. 27, 2021, 11:55 a.m. UTC | #2
On Sat, Nov 27, 2021 at 11:28:05AM +0200, Oskari Lemmelä wrote:
> Hi,
> 
> On 25.11.2021 3.06, Daniel Golle wrote:
> > Import patchset allowing loading and applying device tree overlays at
> > run-time via configfs.
> > 
> > This will allow for packaging DTOs for hardware add-ons such as the
> > various HATs (Hardware Attached on Top) common for SBCs.
> > A new kernel config option CONFIG_OF_CONFIGFS is introduced and some
> > additional sysfs attributes are added in case CONFIG_OF_OVERLAY is
> > enabled.
> 
> Is this something that did not get accepted by upstream linux?
> Those patches seem to be almost 8 years old.

I didn't investigate the full history of that patchset, I just found
it to be the default and only way available to modify DT from
user-space (and hence useful for SBC targets).

Quite a few trees on git.kernel.org come with that patch on top and
when looking for DT overlay documentation, the docs assume you got that
patch applied [1], [2]...

[1]: https://elinux.org/R-Car/DT-Overlays
[2]: https://www.96boards.org/documentation/consumer/dragonboard/dragonboard410c/guides/dt-overlays.md.html#3-load-overlays-dynamically
Oskari Lemmelä Nov. 27, 2021, 12:24 p.m. UTC | #3
Hi,

On 27.11.2021 13.55, Daniel Golle wrote:
> On Sat, Nov 27, 2021 at 11:28:05AM +0200, Oskari Lemmelä wrote:
>> Hi,
>>
>> On 25.11.2021 3.06, Daniel Golle wrote:
>>> Import patchset allowing loading and applying device tree overlays at
>>> run-time via configfs.
>>>
>>> This will allow for packaging DTOs for hardware add-ons such as the
>>> various HATs (Hardware Attached on Top) common for SBCs.
>>> A new kernel config option CONFIG_OF_CONFIGFS is introduced and some
>>> additional sysfs attributes are added in case CONFIG_OF_OVERLAY is
>>> enabled.
>>
>> Is this something that did not get accepted by upstream linux?
>> Those patches seem to be almost 8 years old.
> 
> I didn't investigate the full history of that patchset, I just found
> it to be the default and only way available to modify DT from
> user-space (and hence useful for SBC targets).
> 

If I remember correctly dynamic runtime DT loading was rejected by linux
community. Many SBC distros used them, but when it did not make to
mainline they have changed strategy.

U-boot dynamic device tree loading have been implemented after that to
do same thing before Linux kernel is loaded.

Oskari

> Quite a few trees on git.kernel.org come with that patch on top and
> when looking for DT overlay documentation, the docs assume you got that
> patch applied [1], [2]...
> 
> [1]: https://elinux.org/R-Car/DT-Overlays
> [2]: https://www.96boards.org/documentation/consumer/dragonboard/dragonboard410c/guides/dt-overlays.md.html#3-load-overlays-dynamically
>
Daniel Golle Nov. 27, 2021, 2:01 p.m. UTC | #4
On Sat, Nov 27, 2021 at 02:24:52PM +0200, Oskari Lemmelä wrote:
> Hi,
> 
> On 27.11.2021 13.55, Daniel Golle wrote:
> > On Sat, Nov 27, 2021 at 11:28:05AM +0200, Oskari Lemmelä wrote:
> >> Hi,
> >>
> >> On 25.11.2021 3.06, Daniel Golle wrote:
> >>> Import patchset allowing loading and applying device tree overlays at
> >>> run-time via configfs.
> >>>
> >>> This will allow for packaging DTOs for hardware add-ons such as the
> >>> various HATs (Hardware Attached on Top) common for SBCs.
> >>> A new kernel config option CONFIG_OF_CONFIGFS is introduced and some
> >>> additional sysfs attributes are added in case CONFIG_OF_OVERLAY is
> >>> enabled.
> >>
> >> Is this something that did not get accepted by upstream linux?
> >> Those patches seem to be almost 8 years old.
> > 
> > I didn't investigate the full history of that patchset, I just found
> > it to be the default and only way available to modify DT from
> > user-space (and hence useful for SBC targets).
> > 
> 
> If I remember correctly dynamic runtime DT loading was rejected by linux
> community. Many SBC distros used them, but when it did not make to
> mainline they have changed strategy.

Oh, ok, sad. Thanks for the background.

> 
> U-boot dynamic device tree loading have been implemented after that to
> do same thing before Linux kernel is loaded.
> 

I know and we are using that to embed DT overlay into uImage.FIT images
for BPi-R64, and for this (SATA vs. PCIe) case it's the best solution
because it's a single choice and may need to be decided before extroot
is mounted (because extroot could be sitting on the SATA disk only
available after DTO is applied).

For a lot of less fundamental user modifications, such as adding an
RTC, enabling a user-added USB port or hooking LoRaWAN to an additional
bit-banged SPI bus, it seems much easier (and sufficient) to load the
DTO early in user-space.


Letting Linux apply DT overlays got two main advantages:

 * works equally well on all DT targets (not all of them even have
   a DT-aware bootloader, most of them come with bootloader which
   doesn't support DTO, think of ramips or ath79...)

 * easy to generate .ipk packages for DTOs (just placing dto in the
   right folder results in having it applied on reboot, it can even be
   loaded right away by post-install script)


Letting U-Boot handle DT overlays has one main disadvantage:

Embedding all possible DTOs into uImage.FIT could result in a huge
number of boot configurations as usually most DTOs can be combined with
other DTOs and we should cover all combinations using boot configs in
FIT then...
If we want U-Boot to load DTOs from filesystem (instead of FIT), that
filesystem needs to exist, first of all. Somethings needs to take care
of creating it, handling potential corruption (fsck), ...
Also FDT itself doesn't ensure integrity (afaik), we would have to wrap
DTOs as FIT or provide some sort of integrity protection mechanism (ie.
hashes we can check somehow)

While none of the above is that tragic if what you are having in mind
is a RaspberryPi sitting on your desk, it does become more tricky for
devices which do not boot off a removable SD card (think: soldered-on
SPI-connected flash typically found inside routers)

However, if this whole approach is a dead-end and will just burden us
with additional maintainance in the long run, we have to find a better
way.


> Oskari
> 
> > Quite a few trees on git.kernel.org come with that patch on top and
> > when looking for DT overlay documentation, the docs assume you got that
> > patch applied [1], [2]...
> > 
> > [1]: https://elinux.org/R-Car/DT-Overlays
> > [2]: https://www.96boards.org/documentation/consumer/dragonboard/dragonboard410c/guides/dt-overlays.md.html#3-load-overlays-dynamically
> > 
> 
> _______________________________________________
> openwrt-devel mailing list
> openwrt-devel@lists.openwrt.org
> https://lists.openwrt.org/mailman/listinfo/openwrt-devel
diff mbox series

Patch

diff --git a/target/linux/generic/config-5.10 b/target/linux/generic/config-5.10
index 4554dc22e3..c1b14443e7 100644
--- a/target/linux/generic/config-5.10
+++ b/target/linux/generic/config-5.10
@@ -4210,6 +4210,7 @@  CONFIG_NMI_LOG_BUF_SHIFT=13
 # CONFIG_OCFS2_FS is not set
 # CONFIG_OCTEONTX2_AF is not set
 # CONFIG_OCTEONTX2_PF is not set
+# CONFIG_OF_CONFIGFS is not set
 # CONFIG_OF_OVERLAY is not set
 CONFIG_OF_RESERVED_MEM=y
 # CONFIG_OF_UNITTEST is not set
diff --git a/target/linux/generic/hack-5.10/230-openwrt_lzma_options.patch b/target/linux/generic/hack-5.10/230-openwrt_lzma_options.patch
index 906527faf9..0e80d1ad2a 100644
--- a/target/linux/generic/hack-5.10/230-openwrt_lzma_options.patch
+++ b/target/linux/generic/hack-5.10/230-openwrt_lzma_options.patch
@@ -23,7 +23,7 @@  Signed-off-by: Imre Kaloz <kaloz@openwrt.org>
  	{ {0x02, 0x21}, "lz4", unlz4 },
 --- a/scripts/Makefile.lib
 +++ b/scripts/Makefile.lib
-@@ -370,7 +370,7 @@ quiet_cmd_bzip2 = BZIP2   $@
+@@ -374,7 +374,7 @@ quiet_cmd_bzip2 = BZIP2   $@
  # ---------------------------------------------------------------------------
  
  quiet_cmd_lzma = LZMA    $@
diff --git a/target/linux/generic/pending-5.10/060-OF-DT-Overlay-configfs-interface-v7.patch b/target/linux/generic/pending-5.10/060-OF-DT-Overlay-configfs-interface-v7.patch
new file mode 100644
index 0000000000..570dd6b4aa
--- /dev/null
+++ b/target/linux/generic/pending-5.10/060-OF-DT-Overlay-configfs-interface-v7.patch
@@ -0,0 +1,395 @@ 
+From 073f612de406b949af513c9ebf4ab0e745ffa969 Mon Sep 17 00:00:00 2001
+From: Pantelis Antoniou <pantelis.antoniou@konsulko.com>
+Date: Wed, 4 Dec 2013 19:32:00 +0200
+Subject: [PATCH 01/10] OF: DT-Overlay configfs interface (v7)
+
+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 v6:
+- Default groups properties API changed.
+
+Changes since v5:
+- New style configfs.
+
+Changes since v4:
+- Loading fix for multiple overlays as found out by
+  Geert Uytterhoeven <geert@linux-m68k.org>
+
+Changes since v3:
+- Fixed compilation on SPARC & Xtensa
+
+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@konsulko.com>
+[geert: Use %zu to format size_t]
+[geert: Rebase to v4.15-rc1]
+[geert: Make cfs_overlay_item_dtbo_{read,write}() and
+	of_cfs_overlay_group static]
+[geert: Let OF_CONFIGFS select OF_FLATTREE to fix sparc all*config]
+[geert: Spelling/grammar s/rationalle of/rationale for/]
+[geert: Rebase on top of commit 39a751a4cb7e4798 ("of: change overlay apply input data from unflattened to FDT")
+Signed-off-by: Geert Uytterhoeven <geert+renesas@glider.be>
+---
+ .../devicetree/configfs-overlays.txt          |  31 ++
+ drivers/of/Kconfig                            |   8 +
+ drivers/of/Makefile                           |   1 +
+ drivers/of/configfs.c                         | 284 ++++++++++++++++++
+ 4 files changed, 324 insertions(+)
+ create mode 100644 Documentation/devicetree/configfs-overlays.txt
+ create mode 100644 drivers/of/configfs.c
+
+--- /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 rationale for 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).
+--- a/drivers/of/Kconfig
++++ b/drivers/of/Kconfig
+@@ -93,6 +93,14 @@ config OF_OVERLAY
+ 	  While this option is selected automatically when needed, you can
+ 	  enable it manually to improve device tree unit test coverage.
+ 
++config OF_CONFIGFS
++	bool "Device Tree Overlay ConfigFS interface"
++	select CONFIGFS_FS
++	select OF_FLATTREE
++	depends on OF_OVERLAY
++	help
++	  Enable a simple user-space driven DT overlay interface.
++
+ config OF_NUMA
+ 	bool
+ 
+--- a/drivers/of/Makefile
++++ b/drivers/of/Makefile
+@@ -1,6 +1,7 @@
+ # SPDX-License-Identifier: GPL-2.0
+ obj-y = base.o device.o platform.o property.o
+ obj-$(CONFIG_OF_KOBJ) += kobj.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
+--- /dev/null
++++ b/drivers/of/configfs.c
+@@ -0,0 +1,281 @@
++/*
++ * Configfs entries for device-tree
++ *
++ * Copyright (C) 2013 - Pantelis Antoniou <panto@antoniou-consulting.com>
++ *
++ * 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/sizes.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, const void *blob,
++			  size_t size)
++{
++	int err;
++
++	err = of_overlay_fdt_apply(blob, size, &overlay->ov_id);
++	if (err < 0)
++		pr_err("%s: Failed to create overlay (err=%d)\n", __func__,
++		       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;
++}
++
++static ssize_t cfs_overlay_item_path_show(struct config_item *item, char *page)
++{
++	return sprintf(page, "%s\n", to_cfs_overlay_item(item)->path);
++}
++
++static ssize_t cfs_overlay_item_path_store(struct config_item *item,
++		const char *page, size_t count)
++{
++	struct cfs_overlay_item *overlay = to_cfs_overlay_item(item);
++	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, overlay->fw->data, overlay->fw->size);
++	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 config_item *item,
++		char *page)
++{
++	return sprintf(page, "%s\n", to_cfs_overlay_item(item)->ov_id >= 0 ?
++					"applied" : "unapplied");
++}
++
++CONFIGFS_ATTR(cfs_overlay_item_, path);
++CONFIGFS_ATTR_RO(cfs_overlay_item_, status);
++
++static struct configfs_attribute *cfs_overlay_attrs[] = {
++	&cfs_overlay_item_attr_path,
++	&cfs_overlay_item_attr_status,
++	NULL,
++};
++
++static ssize_t cfs_overlay_item_dtbo_read(struct config_item *item, void *buf,
++		size_t max_count)
++{
++	struct cfs_overlay_item *overlay = to_cfs_overlay_item(item);
++
++	pr_debug("%s: buf=%p max_count=%zu\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;
++}
++
++static ssize_t cfs_overlay_item_dtbo_write(struct config_item *item,
++		const void *buf, size_t count)
++{
++	struct cfs_overlay_item *overlay = to_cfs_overlay_item(item);
++	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, overlay->dtbo_size);
++	if (err < 0)
++		goto out_err;
++
++	return count;
++
++out_err:
++	kfree(overlay->dtbo);
++	overlay->dtbo = NULL;
++	overlay->dtbo_size = 0;
++
++	return err;
++}
++
++CONFIGFS_BIN_ATTR(cfs_overlay_item_, dtbo, NULL, SZ_1M);
++
++static struct configfs_bin_attribute *cfs_overlay_bin_attrs[] = {
++	&cfs_overlay_item_attr_dtbo,
++	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_remove(&overlay->ov_id);
++	if (overlay->fw)
++		release_firmware(overlay->fw);
++	/* kfree with NULL is safe */
++	kfree(overlay->dtbo);
++	kfree(overlay);
++}
++
++static struct configfs_item_operations cfs_overlay_item_ops = {
++	.release		= cfs_overlay_release,
++};
++
++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,
++};
++
++static struct config_group of_cfs_overlay_group;
++
++static struct configfs_subsystem of_cfs_subsys = {
++	.su_group = {
++		.cg_item = {
++			.ci_namebuf = "device-tree",
++			.ci_type = &of_cfs_type,
++		},
++	},
++	.su_mutex = __MUTEX_INITIALIZER(of_cfs_subsys.su_mutex),
++};
++
++static int __init of_cfs_init(void)
++{
++	int ret;
++
++	config_group_init(&of_cfs_subsys.su_group);
++	config_group_init_type_name(&of_cfs_overlay_group, "overlays",
++			&overlays_type);
++	configfs_add_default_group(&of_cfs_overlay_group,
++			&of_cfs_subsys.su_group);
++
++	ret = configfs_register_subsystem(&of_cfs_subsys);
++	if (ret != 0) {
++		pr_err("%s: failed to register subsys\n", __func__);
++		goto out;
++	}
++out:
++	return ret;
++}
++late_initcall(of_cfs_init);
diff --git a/target/linux/generic/pending-5.10/061-of-overlay-kobjectify-overlay-objects.patch b/target/linux/generic/pending-5.10/061-of-overlay-kobjectify-overlay-objects.patch
new file mode 100644
index 0000000000..58074c20af
--- /dev/null
+++ b/target/linux/generic/pending-5.10/061-of-overlay-kobjectify-overlay-objects.patch
@@ -0,0 +1,157 @@ 
+From 77ce59e9749c6214f2304fee7d39ac66a2c79bf1 Mon Sep 17 00:00:00 2001
+From: Pantelis Antoniou <pantelis.antoniou@konsulko.com>
+Date: Sun, 15 Mar 2015 20:39:36 +0200
+Subject: [PATCH 02/10] of: overlay: kobjectify overlay objects
+
+We are going to need the overlays to appear on sysfs with runtime
+global properties (like master enable) so turn them into kobjects.
+
+They have to be in sysfs so that people can have information about the
+overlays applied in the system, i.e. where their targets are and whether
+removal is possible. In a future more attributes can be added
+in a backwards compatible manner.
+
+Signed-off-by: Pantelis Antoniou <pantelis.antoniou@konsulko.com>
+[geert: Rebase to v4.15-rc1]
+[Fengguang Wu: Make overlay_changeset_release() static]
+[geert: Rebase on top of commit 39a751a4cb7e4798 ("of: change overlay apply input data from unflattened to FDT")
+Signed-off-by: Geert Uytterhoeven <geert+renesas@glider.be>
+---
+ drivers/of/base.c       |  5 +++++
+ drivers/of/of_private.h |  9 ++++++++
+ drivers/of/overlay.c    | 48 +++++++++++++++++++++++++++++++++++++++++
+ 3 files changed, 62 insertions(+)
+
+--- a/drivers/of/base.c
++++ b/drivers/of/base.c
+@@ -166,6 +166,7 @@ void __of_phandle_cache_inv_entry(phandl
+ void __init of_core_init(void)
+ {
+ 	struct device_node *np;
++	int ret;
+ 
+ 
+ 	/* Create the kset, and register existing nodes */
+@@ -186,6 +187,10 @@ void __init of_core_init(void)
+ 	/* Symlink in /proc as required by userspace ABI */
+ 	if (of_root)
+ 		proc_symlink("device-tree", NULL, "/sys/firmware/devicetree/base");
++
++	ret = of_overlay_init();
++	if (ret != 0)
++		pr_warn("of_init: of_overlay_init failed!\n");
+ }
+ 
+ static struct property *__of_find_property(const struct device_node *np,
+--- a/drivers/of/of_private.h
++++ b/drivers/of/of_private.h
+@@ -169,4 +169,13 @@ static inline int of_dma_get_range(struc
+ }
+ #endif
+ 
++#if defined(CONFIG_OF_OVERLAY)
++extern int of_overlay_init(void);
++#else
++static inline int of_overlay_init(void)
++{
++	return 0;
++}
++#endif
++
+ #endif /* _LINUX_OF_PRIVATE_H */
+--- a/drivers/of/overlay.c
++++ b/drivers/of/overlay.c
+@@ -20,6 +20,7 @@
+ #include <linux/libfdt.h>
+ #include <linux/err.h>
+ #include <linux/idr.h>
++#include <linux/sysfs.h>
+ 
+ #include "of_private.h"
+ 
+@@ -73,6 +74,7 @@ struct overlay_changeset {
+ 	struct fragment *fragments;
+ 	bool symbols_fragment;
+ 	struct of_changeset cset;
++	struct kobject kobj;
+ };
+ 
+ /* flags are sticky - once set, do not reset */
+@@ -860,6 +862,18 @@ static void free_overlay_changeset(struc
+ 		of_node_put(ovcs->fragments[i].overlay);
+ 	}
+ 	kfree(ovcs->fragments);
++	kobject_put(&ovcs->kobj);
++}
++
++static inline struct overlay_changeset *kobj_to_ovcs(struct kobject *kobj)
++{
++	return container_of(kobj, struct overlay_changeset, kobj);
++}
++
++static void overlay_changeset_release(struct kobject *kobj)
++{
++	struct overlay_changeset *ovcs = kobj_to_ovcs(kobj);
++
+ 	/*
+ 	 * There should be no live pointers into ovcs->overlay_tree and
+ 	 * ovcs->fdt due to the policy that overlay notifiers are not allowed
+@@ -870,6 +884,12 @@ static void free_overlay_changeset(struc
+ 	kfree(ovcs);
+ }
+ 
++static struct kobj_type overlay_changeset_ktype = {
++	.release = overlay_changeset_release,
++};
++
++static struct kset *ov_kset;
++
+ /*
+  * internal documentation
+  *
+@@ -940,6 +960,8 @@ static int of_overlay_apply(const void *
+ 		goto out;
+ 	}
+ 
++	kobject_init(&ovcs->kobj, &overlay_changeset_ktype);
++
+ 	of_overlay_mutex_lock();
+ 	mutex_lock(&of_mutex);
+ 
+@@ -977,6 +999,22 @@ static int of_overlay_apply(const void *
+ 		goto err_free_overlay_changeset;
+ 	}
+ 
++	ovcs->kobj.kset = ov_kset;
++	ret = kobject_add(&ovcs->kobj, NULL, "%d", ovcs->id);
++	if (ret != 0) {
++		pr_err("%s: kobject_add() failed for tree@%s\n", __func__,
++				tree->full_name);
++		ret_tmp = 0;
++		ret_revert = __of_changeset_revert_entries(&ovcs->cset,
++							   &ret_tmp);
++		if (ret_revert) {
++			pr_debug("overlay changeset revert error %d\n",
++				 ret_revert);
++			devicetree_state_flags |= DTSF_REVERT_FAIL;
++		}
++		goto err_free_overlay_changeset;
++	}
++
+ 	ret = __of_changeset_apply_notify(&ovcs->cset);
+ 	if (ret)
+ 		pr_err("overlay apply changeset entry notify error %d\n", ret);
+@@ -1276,3 +1314,13 @@ int of_overlay_remove_all(void)
+ 	return 0;
+ }
+ EXPORT_SYMBOL_GPL(of_overlay_remove_all);
++
++/* called from of_init() */
++int of_overlay_init(void)
++{
++	ov_kset = kset_create_and_add("overlays", NULL, &of_kset->kobj);
++	if (!ov_kset)
++		return -ENOMEM;
++
++	return 0;
++}
diff --git a/target/linux/generic/pending-5.10/062-of-overlay-global-sysfs-enable-attribute.patch b/target/linux/generic/pending-5.10/062-of-overlay-global-sysfs-enable-attribute.patch
new file mode 100644
index 0000000000..a7c1e3acb1
--- /dev/null
+++ b/target/linux/generic/pending-5.10/062-of-overlay-global-sysfs-enable-attribute.patch
@@ -0,0 +1,105 @@ 
+From 2d02a48f61ad600a0d26ae066f8ffa2ba789340f Mon Sep 17 00:00:00 2001
+From: Pantelis Antoniou <pantelis.antoniou@konsulko.com>
+Date: Tue, 17 Mar 2015 15:25:46 +0200
+Subject: [PATCH 03/10] of: overlay: global sysfs enable attribute
+
+A throw once master enable switch to protect against any
+further overlay applications if the administrator desires so.
+
+A kernel command line option is provided as well.
+
+Signed-off-by: Pantelis Antoniou <pantelis.antoniou@konsulko.com>
+---
+ drivers/of/overlay.c | 51 +++++++++++++++++++++++++++++++++++++++++++-
+ 1 file changed, 50 insertions(+), 1 deletion(-)
+
+--- a/drivers/of/overlay.c
++++ b/drivers/of/overlay.c
+@@ -21,6 +21,7 @@
+ #include <linux/err.h>
+ #include <linux/idr.h>
+ #include <linux/sysfs.h>
++#include <linux/atomic.h>
+ 
+ #include "of_private.h"
+ 
+@@ -77,6 +78,16 @@ struct overlay_changeset {
+ 	struct kobject kobj;
+ };
+ 
++/* master enable switch; once set to 0 can't be re-enabled */
++static atomic_t ov_enable = ATOMIC_INIT(1);
++
++static int __init of_overlay_disable_setup(char *str __always_unused)
++{
++	atomic_set(&ov_enable, 0);
++	return 1;
++}
++__setup("of_overlay_disable", of_overlay_disable_setup);
++
+ /* flags are sticky - once set, do not reset */
+ static int devicetree_state_flags;
+ #define DTSF_APPLY_FAIL		0x01
+@@ -884,6 +895,35 @@ static void overlay_changeset_release(st
+ 	kfree(ovcs);
+ }
+ 
++static ssize_t enable_show(struct kobject *kobj,
++		struct kobj_attribute *attr, char *buf)
++{
++	return snprintf(buf, PAGE_SIZE, "%d\n", atomic_read(&ov_enable));
++}
++
++static ssize_t enable_store(struct kobject *kobj,
++		struct kobj_attribute *attr, const char *buf, size_t count)
++{
++	int ret;
++	bool new_enable;
++
++	ret = strtobool(buf, &new_enable);
++	if (ret != 0)
++		return ret;
++	/* if we've disabled it, no going back */
++	if (atomic_read(&ov_enable) == 0)
++		return -EPERM;
++	atomic_set(&ov_enable, (int)new_enable);
++	return count;
++}
++
++static struct kobj_attribute enable_attr = __ATTR_RW(enable);
++
++static const struct attribute *overlay_global_attrs[] = {
++	&enable_attr.attr,
++	NULL
++};
++
+ static struct kobj_type overlay_changeset_ktype = {
+ 	.release = overlay_changeset_release,
+ };
+@@ -944,6 +984,10 @@ static int of_overlay_apply(const void *
+ 	 * overlay changeset code is responsible for freeing them.
+ 	 */
+ 
++	/* administratively disabled */
++	if (!atomic_read(&ov_enable))
++		return -EPERM;
++
+ 	if (devicetree_corrupt()) {
+ 		pr_err("devicetree state suspect, refuse to apply overlay\n");
+ 		kfree(fdt);
+@@ -1318,9 +1362,14 @@ EXPORT_SYMBOL_GPL(of_overlay_remove_all)
+ /* called from of_init() */
+ int of_overlay_init(void)
+ {
++	int rc;
++
+ 	ov_kset = kset_create_and_add("overlays", NULL, &of_kset->kobj);
+ 	if (!ov_kset)
+ 		return -ENOMEM;
+ 
+-	return 0;
++	rc = sysfs_create_files(&ov_kset->kobj, overlay_global_attrs);
++	WARN(rc, "%s: error adding global attributes\n", __func__);
++
++	return rc;
+ }
diff --git a/target/linux/generic/pending-5.10/063-Documentation-ABI-overlays-global-attributes.patch b/target/linux/generic/pending-5.10/063-Documentation-ABI-overlays-global-attributes.patch
new file mode 100644
index 0000000000..6d27736dad
--- /dev/null
+++ b/target/linux/generic/pending-5.10/063-Documentation-ABI-overlays-global-attributes.patch
@@ -0,0 +1,40 @@ 
+From 5b049c3791da89d37bc641ababdcb17359460ca4 Mon Sep 17 00:00:00 2001
+From: Pantelis Antoniou <pantelis.antoniou@konsulko.com>
+Date: Tue, 17 Mar 2015 21:42:10 +0200
+Subject: [PATCH 04/10] Documentation: ABI: overlays - global attributes
+
+Documentation ABI entry for overlays sysfs entries.
+
+Signed-off-by: Pantelis Antoniou <pantelis.antoniou@konsulko.com>
+---
+ .../sysfs-firmware-devicetree-overlays        | 24 +++++++++++++++++++
+ 1 file changed, 24 insertions(+)
+ create mode 100644 Documentation/ABI/testing/sysfs-firmware-devicetree-overlays
+
+--- /dev/null
++++ b/Documentation/ABI/testing/sysfs-firmware-devicetree-overlays
+@@ -0,0 +1,24 @@
++What:		/sys/firmware/devicetree/overlays/
++Date:		October 2015
++Contact:	Pantelis Antoniou <pantelis.antoniou@konsulko.com>
++Description:
++		This directory contains the applied device tree overlays of
++		the running system, as directories of the overlay id.
++
++What:		/sys/firmware/devicetree/overlays/enable
++Date:		October 2015
++Contact:	Pantelis Antoniou <pantelis.antoniou@konsulko.com>
++Description:
++		The master enable switch, by default is 1, and when
++		set to 0 it cannot be re-enabled for security reasons.
++
++		The discussion about this switch takes place in:
++		http://comments.gmane.org/gmane.linux.drivers.devicetree/101871
++
++		Kees Cook:
++		"Coming from the perspective of drawing a bright line between
++		kernel and the root user (which tends to start with disabling
++		kernel module loading), I would say that there at least needs
++		to be a high-level one-way "off" switch for the interface so
++		that systems that have this interface can choose to turn it off
++		during initial boot, etc."
diff --git a/target/linux/generic/pending-5.10/064-Documentation-document-of_overlay_disable-parameter.patch b/target/linux/generic/pending-5.10/064-Documentation-document-of_overlay_disable-parameter.patch
new file mode 100644
index 0000000000..2abd926979
--- /dev/null
+++ b/target/linux/generic/pending-5.10/064-Documentation-document-of_overlay_disable-parameter.patch
@@ -0,0 +1,23 @@ 
+From 4abe0d08fbeb98e385373379b99783ca0749e5ea Mon Sep 17 00:00:00 2001
+From: Pantelis Antoniou <pantelis.antoniou@konsulko.com>
+Date: Thu, 22 Oct 2015 22:37:06 +0300
+Subject: [PATCH 05/10] Documentation: document of_overlay_disable parameter
+
+Document the of_overlay_disable parameter.
+
+Signed-off-by: Pantelis Antoniou <pantelis.antoniou@konsulko.com>
+---
+ Documentation/admin-guide/kernel-parameters.txt | 2 ++
+ 1 file changed, 2 insertions(+)
+
+--- a/Documentation/admin-guide/kernel-parameters.txt
++++ b/Documentation/admin-guide/kernel-parameters.txt
+@@ -3441,6 +3441,8 @@
+ 			This can be set from sysctl after boot.
+ 			See Documentation/admin-guide/sysctl/vm.rst for details.
+ 
++	of_overlay_disable	[OF] Disable device tree overlays at boot time.
++
+ 	ohci1394_dma=early	[HW] enable debugging via the ohci1394 driver.
+ 			See Documentation/core-api/debugging-via-ohci1394.rst for more
+ 			info.
diff --git a/target/linux/generic/pending-5.10/065-of-overlay-add-per-overlay-sysfs-attributes.patch b/target/linux/generic/pending-5.10/065-of-overlay-add-per-overlay-sysfs-attributes.patch
new file mode 100644
index 0000000000..a5deb12a85
--- /dev/null
+++ b/target/linux/generic/pending-5.10/065-of-overlay-add-per-overlay-sysfs-attributes.patch
@@ -0,0 +1,243 @@ 
+From 2de7bb11c440f0116ce0ab25286b66faf6016984 Mon Sep 17 00:00:00 2001
+From: Pantelis Antoniou <pantelis.antoniou@konsulko.com>
+Date: Thu, 23 Apr 2015 19:02:16 +0300
+Subject: [PATCH 06/10] of: overlay: add per overlay sysfs attributes
+
+* A per overlay can_remove sysfs attribute that reports whether
+the overlay can be removed or not due to another overlapping overlay.
+
+* A target sysfs attribute listing the target of each fragment,
+in a group named after the name of the fragment.
+
+Signed-off-by: Pantelis Antoniou <pantelis.antoniou@konsulko.com>
+[geert: Setup ovinfo[cnt].info for symbols]
+[geert: Spelling s/changset/changeset/]
+[geert: Rebase on top of commit 39a751a4cb7e4798 ("of: change overlay apply input data from unflattened to FDT")
+[geert: Use "%pOF" instead of of_node_full_name()]
+Signed-off-by: Geert Uytterhoeven <geert+renesas@glider.be>
+---
+ drivers/of/overlay.c | 111 +++++++++++++++++++++++++++++++++++++++----
+ 1 file changed, 101 insertions(+), 10 deletions(-)
+
+--- a/drivers/of/overlay.c
++++ b/drivers/of/overlay.c
+@@ -25,6 +25,20 @@
+ 
+ #include "of_private.h"
+ 
++/* fwd. decl */
++struct overlay_changeset;
++struct fragment;
++
++/* an attribute for each fragment */
++struct fragment_attribute {
++	struct attribute attr;
++	ssize_t (*show)(struct kobject *kobj, struct fragment_attribute *fattr,
++			char *buf);
++	ssize_t (*store)(struct kobject *kobj, struct fragment_attribute *fattr,
++			 const char *buf, size_t count);
++	struct fragment *fragment;
++};
++
+ /**
+  * struct target - info about current target node as recursing through overlay
+  * @np:			node where current level of overlay will be applied
+@@ -47,12 +61,18 @@ struct target {
+ 
+ /**
+  * struct fragment - info about fragment nodes in overlay expanded device tree
++ * @info:	info node that contains the target and overlay
+  * @target:	target of the overlay operation
+  * @overlay:	pointer to the __overlay__ node
+  */
+ struct fragment {
+ 	struct device_node *overlay;
+ 	struct device_node *target;
++	struct overlay_changeset *ovcs;
++	struct device_node *info;
++	struct attribute_group attr_group;
++	struct attribute *attrs[2];
++	struct fragment_attribute target_attr;
+ };
+ 
+ /**
+@@ -73,6 +93,7 @@ struct overlay_changeset {
+ 	struct device_node *overlay_tree;
+ 	int count;
+ 	struct fragment *fragments;
++	const struct attribute_group **attr_groups;
+ 	bool symbols_fragment;
+ 	struct of_changeset cset;
+ 	struct kobject kobj;
+@@ -106,6 +127,7 @@ static int devicetree_corrupt(void)
+ 
+ static int build_changeset_next_level(struct overlay_changeset *ovcs,
+ 		struct target *target, const struct device_node *overlay_node);
++static int overlay_removal_is_ok(struct overlay_changeset *ovcs);
+ 
+ /*
+  * of_resolve_phandles() finds the largest phandle in the live tree.
+@@ -729,6 +751,16 @@ static struct device_node *find_target(s
+ 	return NULL;
+ }
+ 
++static ssize_t target_show(struct kobject *kobj,
++			   struct fragment_attribute *fattr, char *buf)
++{
++	struct fragment *fragment = fattr->fragment;
++
++	return snprintf(buf, PAGE_SIZE, "%pOF\n", fragment->target);
++}
++
++static const struct fragment_attribute target_template_attr = __ATTR_RO(target);
++
+ /**
+  * init_overlay_changeset() - initialize overlay changeset from overlay tree
+  * @ovcs:	Overlay changeset to build
+@@ -748,7 +780,7 @@ static int init_overlay_changeset(struct
+ 	struct device_node *node, *overlay_node;
+ 	struct fragment *fragment;
+ 	struct fragment *fragments;
+-	int cnt, id, ret;
++	int i, cnt, id, ret;
+ 
+ 	/*
+ 	 * Warn for some issues.  Can not return -EINVAL for these until
+@@ -813,6 +845,7 @@ static int init_overlay_changeset(struct
+ 			goto err_free_fragments;
+ 		}
+ 
++		fragment->info = of_node_get(node);
+ 		cnt++;
+ 	}
+ 
+@@ -833,6 +866,7 @@ static int init_overlay_changeset(struct
+ 			goto err_free_fragments;
+ 		}
+ 
++		fragment->info = of_node_get(node);
+ 		cnt++;
+ 	}
+ 
+@@ -846,6 +880,34 @@ static int init_overlay_changeset(struct
+ 	ovcs->count = cnt;
+ 	ovcs->fragments = fragments;
+ 
++	ovcs->attr_groups = kcalloc(cnt + 1, sizeof(struct attribute_group *),
++				    GFP_KERNEL);
++	if (ovcs->attr_groups == NULL) {
++		ret = -ENOMEM;
++		goto err_free_fragments;
++	}
++
++	for (i = 0; i < cnt; i++) {
++		fragment = &ovcs->fragments[i];
++
++		ovcs->attr_groups[i] = &fragment->attr_group;
++
++		fragment->target_attr = target_template_attr;
++		/* make lockdep happy */
++		sysfs_attr_init(&fragment->target_attr.attr);
++		fragment->target_attr.fragment = fragment;
++
++		fragment->attrs[0] = &fragment->target_attr.attr;
++		fragment->attrs[1] = NULL;
++
++		/* NOTE: direct reference to the full_name */
++		fragment->attr_group.name =
++			kbasename(fragment->info->full_name);
++		fragment->attr_group.attrs = fragment->attrs;
++
++	}
++	ovcs->attr_groups[i] = NULL;
++
+ 	return 0;
+ 
+ err_free_fragments:
+@@ -868,9 +930,12 @@ static void free_overlay_changeset(struc
+ 	if (ovcs->id)
+ 		idr_remove(&ovcs_idr, ovcs->id);
+ 
++	kfree(ovcs->attr_groups);
++
+ 	for (i = 0; i < ovcs->count; i++) {
+ 		of_node_put(ovcs->fragments[i].target);
+ 		of_node_put(ovcs->fragments[i].overlay);
++		of_node_put(ovcs->fragments[i].info);
+ 	}
+ 	kfree(ovcs->fragments);
+ 	kobject_put(&ovcs->kobj);
+@@ -924,8 +989,25 @@ static const struct attribute *overlay_g
+ 	NULL
+ };
+ 
++static ssize_t can_remove_show(struct kobject *kobj,
++		struct kobj_attribute *attr, char *buf)
++{
++	struct overlay_changeset *ovcs = kobj_to_ovcs(kobj);
++
++	return snprintf(buf, PAGE_SIZE, "%d\n", overlay_removal_is_ok(ovcs));
++}
++
++static struct kobj_attribute can_remove_attr = __ATTR_RO(can_remove);
++
++static struct attribute *overlay_changeset_attrs[] = {
++	&can_remove_attr.attr,
++	NULL
++};
++
+ static struct kobj_type overlay_changeset_ktype = {
+ 	.release = overlay_changeset_release,
++	.sysfs_ops = &kobj_sysfs_ops,	/* default kobj sysfs ops */
++	.default_attrs = overlay_changeset_attrs,
+ };
+ 
+ static struct kset *ov_kset;
+@@ -1048,15 +1130,14 @@ static int of_overlay_apply(const void *
+ 	if (ret != 0) {
+ 		pr_err("%s: kobject_add() failed for tree@%s\n", __func__,
+ 				tree->full_name);
+-		ret_tmp = 0;
+-		ret_revert = __of_changeset_revert_entries(&ovcs->cset,
+-							   &ret_tmp);
+-		if (ret_revert) {
+-			pr_debug("overlay changeset revert error %d\n",
+-				 ret_revert);
+-			devicetree_state_flags |= DTSF_REVERT_FAIL;
+-		}
+-		goto err_free_overlay_changeset;
++		goto err_revert;
++	}
++
++	ret = sysfs_create_groups(&ovcs->kobj, ovcs->attr_groups);
++	if (ret != 0) {
++		pr_err("%s: sysfs_create_groups() failed for tree@%s\n",
++				__func__, tree->full_name);
++		goto err_revert;
+ 	}
+ 
+ 	ret = __of_changeset_apply_notify(&ovcs->cset);
+@@ -1077,6 +1158,14 @@ static int of_overlay_apply(const void *
+ 
+ 	goto out_unlock;
+ 
++err_revert:
++	ret_tmp = 0;
++	ret_revert = __of_changeset_revert_entries(&ovcs->cset, &ret_tmp);
++	if (ret_revert) {
++		pr_debug("overlay changeset revert error %d\n", ret_revert);
++		devicetree_state_flags |= DTSF_REVERT_FAIL;
++	}
++
+ err_free_tree:
+ 	kfree(fdt);
+ 	kfree(tree);
+@@ -1301,6 +1390,8 @@ int of_overlay_remove(int *ovcs_id)
+ 
+ 	list_del(&ovcs->ovcs_list);
+ 
++	sysfs_remove_groups(&ovcs->kobj, ovcs->attr_groups);
++
+ 	ret_apply = 0;
+ 	ret = __of_changeset_revert_entries(&ovcs->cset, &ret_apply);
+ 	if (ret) {
diff --git a/target/linux/generic/pending-5.10/066-Documentation-ABI-overlays-per-overlay-docs.patch b/target/linux/generic/pending-5.10/066-Documentation-ABI-overlays-per-overlay-docs.patch
new file mode 100644
index 0000000000..668b27b83d
--- /dev/null
+++ b/target/linux/generic/pending-5.10/066-Documentation-ABI-overlays-per-overlay-docs.patch
@@ -0,0 +1,46 @@ 
+From a85092f9d149e00510cce1885655dc9084a62f9b Mon Sep 17 00:00:00 2001
+From: Pantelis Antoniou <pantelis.antoniou@konsulko.com>
+Date: Thu, 22 Oct 2015 20:59:27 +0300
+Subject: [PATCH 07/10] Documentation: ABI: overlays - per overlay docs
+
+Documentation for the per-overlay attributes.
+
+Signed-off-by: Pantelis Antoniou <pantelis.antoniou@konsulko.com>
+---
+ .../sysfs-firmware-devicetree-overlays        | 28 +++++++++++++++++++
+ 1 file changed, 28 insertions(+)
+
+--- a/Documentation/ABI/testing/sysfs-firmware-devicetree-overlays
++++ b/Documentation/ABI/testing/sysfs-firmware-devicetree-overlays
+@@ -22,3 +22,31 @@ Description:
+ 		to be a high-level one-way "off" switch for the interface so
+ 		that systems that have this interface can choose to turn it off
+ 		during initial boot, etc."
++
++What:		/sys/firmware/devicetree/overlays/<id>
++Date:		October 2015
++Contact:	Pantelis Antoniou <pantelis.antoniou@konsulko.com>
++Description:
++		Each directory represents an applied overlay, containing
++		the following attribute files.
++
++What:		/sys/firmware/devicetree/overlays/<id>/can_remove
++Date:		October 2015
++Contact:	Pantelis Antoniou <pantelis.antoniou@konsulko.com>
++Description:
++		The attribute set to 1 means that the overlay can be removed,
++		while 0 means that the overlay is being overlapped therefore
++		removal is prohibited.
++
++What:		/sys/firmware/devicetree/overlays/<id>/<fragment-name>/
++Date:		October 2015
++Contact:	Pantelis Antoniou <pantelis.antoniou@konsulko.com>
++Description:
++		Each of these directories contain information about of the
++		particular overlay fragment.
++
++What:		/sys/firmware/devicetree/overlays/<id>/<fragment-name>/target
++Date:		October 2015
++Contact:	Pantelis Antoniou <pantelis.antoniou@konsulko.com>
++Description:
++		The full-path of the target of the fragment
diff --git a/target/linux/generic/pending-5.10/067-of-rename-_node_sysfs-to-_node_post.patch b/target/linux/generic/pending-5.10/067-of-rename-_node_sysfs-to-_node_post.patch
new file mode 100644
index 0000000000..f805e0ce8a
--- /dev/null
+++ b/target/linux/generic/pending-5.10/067-of-rename-_node_sysfs-to-_node_post.patch
@@ -0,0 +1,150 @@ 
+From 7e2d9ac81a7abb2a9d8a75c045c0adb357bbf403 Mon Sep 17 00:00:00 2001
+From: Pantelis Antoniou <pantelis.antoniou@konsulko.com>
+Date: Wed, 14 Oct 2015 13:20:54 +0300
+Subject: [PATCH 08/10] of: rename *_node_sysfs to _node_post
+
+Signed-off-by: Pantelis Antoniou <pantelis.antoniou@konsulko.com>
+[geert: Convert new user in of_unittest_overlay_high_level()]
+[geert: Rebase to v4.15-rc1]
+[geert: Rebase on top of commit 39a751a4cb7e4798 ("of: change overlay apply input data from unflattened to FDT")
+Signed-off-by: Geert Uytterhoeven <geert+renesas@glider.be>
+---
+ drivers/of/base.c       |  2 +-
+ drivers/of/dynamic.c    |  8 ++++----
+ drivers/of/kobj.c       |  4 ++--
+ drivers/of/of_private.h | 12 ++++++------
+ drivers/of/unittest.c   |  6 +++---
+ 5 files changed, 16 insertions(+), 16 deletions(-)
+
+--- a/drivers/of/base.c
++++ b/drivers/of/base.c
+@@ -178,7 +178,7 @@ void __init of_core_init(void)
+ 		return;
+ 	}
+ 	for_each_of_allnodes(np) {
+-		__of_attach_node_sysfs(np);
++		__of_attach_node_post(np);
+ 		if (np->phandle && !phandle_cache[of_phandle_cache_hash(np->phandle)])
+ 			phandle_cache[of_phandle_cache_hash(np->phandle)] = np;
+ 	}
+--- a/drivers/of/dynamic.c
++++ b/drivers/of/dynamic.c
+@@ -243,7 +243,7 @@ int of_attach_node(struct device_node *n
+ 	__of_attach_node(np);
+ 	raw_spin_unlock_irqrestore(&devtree_lock, flags);
+ 
+-	__of_attach_node_sysfs(np);
++	__of_attach_node_post(np);
+ 	mutex_unlock(&of_mutex);
+ 
+ 	of_reconfig_notify(OF_RECONFIG_ATTACH_NODE, &rd);
+@@ -295,7 +295,7 @@ int of_detach_node(struct device_node *n
+ 	__of_detach_node(np);
+ 	raw_spin_unlock_irqrestore(&devtree_lock, flags);
+ 
+-	__of_detach_node_sysfs(np);
++	__of_detach_node_post(np);
+ 	mutex_unlock(&of_mutex);
+ 
+ 	of_reconfig_notify(OF_RECONFIG_DETACH_NODE, &rd);
+@@ -634,10 +634,10 @@ static int __of_changeset_entry_apply(st
+ 
+ 	switch (ce->action) {
+ 	case OF_RECONFIG_ATTACH_NODE:
+-		__of_attach_node_sysfs(ce->np);
++		__of_attach_node_post(ce->np);
+ 		break;
+ 	case OF_RECONFIG_DETACH_NODE:
+-		__of_detach_node_sysfs(ce->np);
++		__of_detach_node_post(ce->np);
+ 		break;
+ 	case OF_RECONFIG_ADD_PROPERTY:
+ 		/* ignore duplicate names */
+--- a/drivers/of/kobj.c
++++ b/drivers/of/kobj.c
+@@ -112,7 +112,7 @@ void __of_update_property_sysfs(struct d
+ 	__of_add_property_sysfs(np, newprop);
+ }
+ 
+-int __of_attach_node_sysfs(struct device_node *np)
++int __of_attach_node_post(struct device_node *np)
+ {
+ 	const char *name;
+ 	struct kobject *parent;
+@@ -146,7 +146,7 @@ int __of_attach_node_sysfs(struct device
+ 	return 0;
+ }
+ 
+-void __of_detach_node_sysfs(struct device_node *np)
++void __of_detach_node_post(struct device_node *np)
+ {
+ 	struct property *pp;
+ 
+--- a/drivers/of/of_private.h
++++ b/drivers/of/of_private.h
+@@ -63,8 +63,8 @@ int __of_add_property_sysfs(struct devic
+ void __of_remove_property_sysfs(struct device_node *np, struct property *prop);
+ void __of_update_property_sysfs(struct device_node *np, struct property *newprop,
+ 		struct property *oldprop);
+-int __of_attach_node_sysfs(struct device_node *np);
+-void __of_detach_node_sysfs(struct device_node *np);
++int __of_attach_node_post(struct device_node *np);
++void __of_detach_node_post(struct device_node *np);
+ #else
+ static inline int __of_add_property_sysfs(struct device_node *np, struct property *pp)
+ {
+@@ -73,11 +73,11 @@ static inline int __of_add_property_sysf
+ static inline void __of_remove_property_sysfs(struct device_node *np, struct property *prop) {}
+ static inline void __of_update_property_sysfs(struct device_node *np,
+ 		struct property *newprop, struct property *oldprop) {}
+-static inline int __of_attach_node_sysfs(struct device_node *np)
++static inline int __of_attach_node_post(struct device_node *np)
+ {
+ 	return 0;
+ }
+-static inline void __of_detach_node_sysfs(struct device_node *np) {}
++static inline void __of_detach_node_post(struct device_node *np) {}
+ #endif
+ 
+ #if defined(CONFIG_OF_RESOLVE)
+@@ -135,9 +135,9 @@ extern int __of_update_property(struct d
+ extern void __of_update_property_sysfs(struct device_node *np,
+ 		struct property *newprop, struct property *oldprop);
+ 
+-extern int __of_attach_node_sysfs(struct device_node *np);
++extern int __of_attach_node_post(struct device_node *np);
+ extern void __of_detach_node(struct device_node *np);
+-extern void __of_detach_node_sysfs(struct device_node *np);
++extern void __of_detach_node_post(struct device_node *np);
+ 
+ extern void __of_sysfs_remove_bin_file(struct device_node *np,
+ 				       struct property *prop);
+--- a/drivers/of/unittest.c
++++ b/drivers/of/unittest.c
+@@ -1391,7 +1391,7 @@ static void attach_node_and_children(str
+ 	of_node_clear_flag(np, OF_DETACHED);
+ 	raw_spin_unlock_irqrestore(&devtree_lock, flags);
+ 
+-	__of_attach_node_sysfs(np);
++	__of_attach_node_post(np);
+ 	mutex_unlock(&of_mutex);
+ 
+ 	while (child) {
+@@ -1451,7 +1451,7 @@ static int __init unittest_data_add(void
+ 	if (!of_root) {
+ 		of_root = unittest_data_node;
+ 		for_each_of_allnodes(np)
+-			__of_attach_node_sysfs(np);
++			__of_attach_node_post(np);
+ 		of_aliases = of_find_node_by_path("/aliases");
+ 		of_chosen = of_find_node_by_path("/chosen");
+ 		of_overlay_mutex_unlock();
+@@ -3115,7 +3115,7 @@ static __init void of_unittest_overlay_h
+ 		of_root->child = overlay_base_root->child;
+ 
+ 	for_each_of_allnodes_from(overlay_base_root, np)
+-		__of_attach_node_sysfs(np);
++		__of_attach_node_post(np);
+ 
+ 	if (of_symbols) {
+ 		struct property *new_prop;
diff --git a/target/linux/generic/pending-5.10/068-kbuild-Enable-DT-symbols-when-CONFIG_OF_OVERLAY-is-u.patch b/target/linux/generic/pending-5.10/068-kbuild-Enable-DT-symbols-when-CONFIG_OF_OVERLAY-is-u.patch
new file mode 100644
index 0000000000..fe4d26ade1
--- /dev/null
+++ b/target/linux/generic/pending-5.10/068-kbuild-Enable-DT-symbols-when-CONFIG_OF_OVERLAY-is-u.patch
@@ -0,0 +1,27 @@ 
+From 09df105083529259874de93f00abc86cb9223b5e Mon Sep 17 00:00:00 2001
+From: Geert Uytterhoeven <geert+renesas@glider.be>
+Date: Wed, 26 Aug 2015 19:21:00 +0200
+Subject: [PATCH 09/10] kbuild: Enable DT symbols when CONFIG_OF_OVERLAY is
+ used
+
+Signed-off-by: Geert Uytterhoeven <geert+renesas@glider.be>
+---
+Replacement for "ARM: DT: Enable symbols when CONFIG_OF_OVERLAY is
+used".
+---
+ scripts/Makefile.lib | 4 ++++
+ 1 file changed, 4 insertions(+)
+
+--- a/scripts/Makefile.lib
++++ b/scripts/Makefile.lib
+@@ -315,6 +315,10 @@ cmd_dt_S_dtb=						\
+ $(obj)/%.dtb.S: $(obj)/%.dtb FORCE
+ 	$(call if_changed,dt_S_dtb)
+ 
++ifeq ($(CONFIG_OF_OVERLAY),y)
++DTC_FLAGS += -@
++endif
++
+ quiet_cmd_dtc = DTC     $@
+ cmd_dtc = $(HOSTCC) -E $(dtc_cpp_flags) -x assembler-with-cpp -o $(dtc-tmp) $< ; \
+ 	$(DTC) -O $(patsubst .%,%,$(suffix $@)) -o $@ -b 0 \