From e438983899b06cf3534b773b6e19cb291456e5cb Mon Sep 17 00:00:00 2001 From: Pantelis Antoniou Date: Wed, 3 Dec 2014 13:23:28 +0200 Subject: [PATCH] OF: DT-Overlay configfs interface This is a port of Pantelis Antoniou's v3 port that makes use of the new upstreamed configfs support for binary attributes. Original commit message: 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(). Originally-signed-off-by: Pantelis Antoniou Signed-off-by: Phil Elwell DT configfs: Fix build errors on other platforms Signed-off-by: Phil Elwell DT configfs: fix build error There is an error when compiling rpi-4.6.y branch: CC drivers/of/configfs.o drivers/of/configfs.c:291:21: error: initialization from incompatible pointer type [-Werror=incompatible-pointer-types] .default_groups = of_cfs_def_groups, ^ drivers/of/configfs.c:291:21: note: (near initialization for 'of_cfs_subsys.su_group.default_groups.next') The .default_groups is linked list since commit 1ae1602de028acaa42a0f6ff18d19756f8e825c6. This commit uses configfs_add_default_group to fix this problem. Signed-off-by: Slawomir Stepien configfs: New of_overlay API of: configfs: Use of_overlay_fdt_apply API call The published API to the dynamic overlay application mechanism now takes a Flattened Device Tree blob as input so that it can manage the lifetime of the unflattened tree. Conveniently, the new API call - of_overlay_fdt_apply - is virtually a drop-in replacement for create_overlay, which can now be deleted. Signed-off-by: Phil Elwell --- .../devicetree/configfs-overlays.txt | 31 ++ drivers/of/Kconfig | 7 + drivers/of/Makefile | 1 + drivers/of/configfs.c | 277 ++++++++++++++++++ 4 files changed, 316 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 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). --- a/drivers/of/Kconfig +++ b/drivers/of/Kconfig @@ -94,4 +94,11 @@ config OF_DMA_DEFAULT_COHERENT # arches should select this if DMA is coherent by default for OF devices bool +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. + endif # OF --- a/drivers/of/Makefile +++ b/drivers/of/Makefile @@ -1,6 +1,7 @@ # SPDX-License-Identifier: GPL-2.0 obj-y = base.o device.o module.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 +1,277 @@ +/* + * Configfs entries for device-tree + * + * Copyright (C) 2013 - Pantelis Antoniou + * + * 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 +#include +#include +#include +#include +#include +#include +#include +#include +#include +#include +#include +#include +#include +#include +#include + +#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 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) +{ + struct cfs_overlay_item *overlay = to_cfs_overlay_item(item); + return sprintf(page, "%s\n", overlay->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 = of_overlay_fdt_apply((void *)overlay->fw->data, + (u32)overlay->fw->size, &overlay->ov_id); + 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) +{ + struct cfs_overlay_item *overlay = to_cfs_overlay_item(item); + + return sprintf(page, "%s\n", + overlay->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, +}; + +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; +} + +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 = of_overlay_fdt_apply(overlay->dtbo, overlay->dtbo_size, + &overlay->ov_id); + if (err != 0) + goto out_err; + + return count; + +out_err: + kfree(overlay->dtbo); + overlay->dtbo = NULL; + overlay->dtbo_size = 0; + overlay->ov_id = 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); + + 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; + +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);