linux 5.4: runtime interface to using configfs for generic device tree overlay

3 files changed, 413 insertions, 2 deletions

diff --git a/recipes-kernel/linux/linux-at91-5.4.81/defconfig b/recipes-kernel/linux/linux-at91-5.4.81/defconfig
index 47ab083..158b96d 100644
--- a/recipes-kernel/linux/linux-at91-5.4.81/defconfig
+++ b/recipes-kernel/linux/linux-at91-5.4.81/defconfig
@@ -1438,6 +1438,7 @@ CONFIG_OF_MDIO=y
 CONFIG_OF_RESERVED_MEM=y
 CONFIG_OF_RESOLVE=y
 CONFIG_OF_OVERLAY=y
+CONFIG_OF_CONFIGFS=y
 CONFIG_ARCH_MIGHT_HAVE_PC_PARPORT=y
 # CONFIG_PARPORT is not set
 CONFIG_BLK_DEV=y
diff --git a/recipes-kernel/linux/linux-at91-5.4.81/linux-5.4-OF-DT-Overlay-configfs-interface.patch b/recipes-kernel/linux/linux-at91-5.4.81/linux-5.4-OF-DT-Overlay-configfs-interface.patch
new file mode 100644
index 0000000..b818a7c
--- /dev/null
+++ b/recipes-kernel/linux/linux-at91-5.4.81/linux-5.4-OF-DT-Overlay-configfs-interface.patch
@@ -0,0 +1,411 @@
+From 746f647c66dc4501b6a2954ffd22a8a0555d10a2 Mon Sep 17 00:00:00 2001
+From: Pantelis Antoniou <pantelis.antoniou@konsulko.com>
+Date: Wed, 4 Dec 2013 19:32:00 +0200
+Subject: 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>
+---
+ Documentation/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
+
+diff --git a/Documentation/devicetree/configfs-overlays.txt b/Documentation/devicetree/configfs-overlays.txt
+new file mode 100644
+index 0000000000000..185d85ef52e49
+--- /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).
+diff --git a/drivers/of/Kconfig b/drivers/of/Kconfig
+index 18450437d5d5a..303737ebce435 100644
+--- 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
+ 
+diff --git a/drivers/of/Makefile b/drivers/of/Makefile
+index 6e1e5212f0589..3222259b03932 100644
+--- 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
+diff --git a/drivers/of/configfs.c b/drivers/of/configfs.c
+new file mode 100644
+index 0000000000000..7a6cae074381c
+--- /dev/null
++++ b/drivers/of/configfs.c
+@@ -0,0 +1,284 @@
++/*
++ * 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;
++
++	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);
++	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;
++	}
++	pr_info("%s: OK\n", __func__);
++out:
++	return ret;
++}
++late_initcall(of_cfs_init);
+-- 
+cgit 1.2.3-1.el7
+
diff --git a/recipes-kernel/linux/linux-at91_5.4.81.bb b/recipes-kernel/linux/linux-at91_5.4.81.bb
index a3151d5..b6e6cdf 100644
--- a/recipes-kernel/linux/linux-at91_5.4.81.bb
+++ b/recipes-kernel/linux/linux-at91_5.4.81.bb
@@ -42,9 +42,8 @@ COMMON_PATCHES = " \
 		  file://linux-5.4-cdc-acm-ignore-exar-devices.patch \
 		  file://EXTRAVERSION.patch \
 		  file://linux-5.4-addl-time-for-pmeccerrloc.patch \
+		  file://linux-5.4-OF-DT-Overlay-configfs-interface.patch \
 "
-# MTS TODO:       file://950-0090-OF-DT-Overlay-configfs-interface.patch
-
 
 SRC_URI_append_mtcdt = "\
             ${COMMON_PATCHES} \