diff options
| -rw-r--r-- | Documentation/devicetree/overlay-notes.txt | 133 | ||||
| -rw-r--r-- | drivers/of/Kconfig | 7 | ||||
| -rw-r--r-- | drivers/of/Makefile | 1 | ||||
| -rw-r--r-- | drivers/of/overlay.c | 562 | ||||
| -rw-r--r-- | include/linux/of.h | 31 |
5 files changed, 734 insertions, 0 deletions
diff --git a/Documentation/devicetree/overlay-notes.txt b/Documentation/devicetree/overlay-notes.txt new file mode 100644 index 0000000..30ae758 --- /dev/null +++ b/Documentation/devicetree/overlay-notes.txt @@ -0,0 +1,133 @@ +Device Tree Overlay Notes +------------------------- + +This document describes the implementation of the in-kernel +device tree overlay functionality residing in drivers/of/overlay.c and is a +companion document to Documentation/devicetree/dt-object-internal.txt[1] & +Documentation/devicetree/dynamic-resolution-notes.txt[2] + +How overlays work +----------------- + +A Device Tree's overlay purpose is to modify the kernel's live tree, and +have the modification affecting the state of the the kernel in a way that +is reflecting the changes. +Since the kernel mainly deals with devices, any new device node that result +in an active device should have it created while if the device node is either +disabled or removed all together, the affected device should be deregistered. + +Lets take an example where we have a foo board with the following base tree +which is taken from [1]. + +---- foo.dts ----------------------------------------------------------------- + /* FOO platform */ + / { + compatible = "corp,foo"; + + /* shared resources */ + res: res { + }; + + /* On chip peripherals */ + ocp: ocp { + /* peripherals that are always instantiated */ + peripheral1 { ... }; + } + }; +---- foo.dts ----------------------------------------------------------------- + +The overlay bar.dts, when loaded (and resolved as described in [2]) should + +---- bar.dts ----------------------------------------------------------------- +/plugin/; /* allow undefined label references and record them */ +/ { + .... /* various properties for loader use; i.e. part id etc. */ + fragment@0 { + target = <&ocp>; + __overlay__ { + /* bar peripheral */ + bar { + compatible = "corp,bar"; + ... /* various properties and child nodes */ + } + }; + }; +}; +---- bar.dts ----------------------------------------------------------------- + +result in foo+bar.dts + +---- foo+bar.dts ------------------------------------------------------------- + /* FOO platform + bar peripheral */ + / { + compatible = "corp,foo"; + + /* shared resources */ + res: res { + }; + + /* On chip peripherals */ + ocp: ocp { + /* peripherals that are always instantiated */ + peripheral1 { ... }; + + /* bar peripheral */ + bar { + compatible = "corp,bar"; + ... /* various properties and child nodes */ + } + } + }; +---- foo+bar.dts ------------------------------------------------------------- + +As a result of the the overlay, a new device node (bar) has been created +so a bar platform device will be registered and if a matching device driver +is loaded the device will be created as expected. + +Overlay in-kernel API +-------------------------------- + +The API is quite easy to use. + +1. Call of_overlay_create() to create and apply an overlay. The return value +is a cookie identifying this overlay. + +2. Call of_overlay_destroy() to remove and cleanup the overlay previously +created via the call to of_overlay_create(). Removal of an overlay that +is stacked by another will not be permitted. + +Finally, if you need to remove all overlays in one-go, just call +of_overlay_destroy_all() which will remove every single one in the correct +order. + +Overlay DTS Format +------------------ + +The DTS of an overlay should have the following format: + +{ + /* ignored properties by the overlay */ + + fragment@0 { /* first child node */ + + target=<phandle>; /* phandle target of the overlay */ + or + target-path="/path"; /* target path of the overlay */ + + __overlay__ { + property-a; /* add property-a to the target */ + node-a { /* add to an existing, or create a node-a */ + ... + }; + }; + } + fragment@1 { /* second child node */ + ... + }; + /* more fragments follow */ +} + +Using the non-phandle based target method allows one to use a base DT which does +not contain a __symbols__ node, i.e. it was not compiled with the -@ option. +The __symbols__ node is only required for the target=<phandle> method, since it +contains the information required to map from a phandle to a tree location. diff --git a/drivers/of/Kconfig b/drivers/of/Kconfig index fbe8f8d..18b2e25 100644 --- a/drivers/of/Kconfig +++ b/drivers/of/Kconfig @@ -84,4 +84,11 @@ config OF_RESERVED_MEM config OF_RESOLVE bool +config OF_OVERLAY + bool + depends on OF + select OF_DYNAMIC + select OF_DEVICE + select OF_RESOLVE + endmenu # OF diff --git a/drivers/of/Makefile b/drivers/of/Makefile index d90553f..7563f36 100644 --- a/drivers/of/Makefile +++ b/drivers/of/Makefile @@ -14,6 +14,7 @@ obj-$(CONFIG_OF_PCI_IRQ) += of_pci_irq.o obj-$(CONFIG_OF_MTD) += of_mtd.o obj-$(CONFIG_OF_RESERVED_MEM) += of_reserved_mem.o obj-$(CONFIG_OF_RESOLVE) += resolver.o +obj-$(CONFIG_OF_OVERLAY) += overlay.o CFLAGS_fdt.o = -I$(src)/../../scripts/dtc/libfdt CFLAGS_fdt_address.o = -I$(src)/../../scripts/dtc/libfdt diff --git a/drivers/of/overlay.c b/drivers/of/overlay.c new file mode 100644 index 0000000..ea63fbd2 --- /dev/null +++ b/drivers/of/overlay.c @@ -0,0 +1,562 @@ +/* + * Functions for working with device tree overlays + * + * Copyright (C) 2012 Pantelis Antoniou <panto@antoniou-consulting.com> + * Copyright (C) 2012 Texas Instruments Inc. + * + * This program is free software; you can redistribute it and/or + * modify it under the terms of the GNU General Public License + * version 2 as published by the Free Software Foundation. + */ +#undef DEBUG +#include <linux/kernel.h> +#include <linux/module.h> +#include <linux/of.h> +#include <linux/of_device.h> +#include <linux/string.h> +#include <linux/ctype.h> +#include <linux/errno.h> +#include <linux/string.h> +#include <linux/slab.h> +#include <linux/err.h> + +#include "of_private.h" + +/** + * struct of_overlay_info - Holds a single overlay info + * @target: target of the overlay operation + * @overlay: pointer to the overlay contents node + * + * Holds a single overlay state, including all the overlay logs & + * records. + */ +struct of_overlay_info { + struct device_node *target; + struct device_node *overlay; +}; + +/** + * struct of_overlay - Holds a complete overlay transaction + * @node: List on which we are located + * @count: Count of ovinfo structures + * @ovinfo_tab: Overlay info table (count sized) + * @cset: Changeset to be used + * + * Holds a complete overlay transaction + */ +struct of_overlay { + int id; + struct list_head node; + int count; + struct of_overlay_info *ovinfo_tab; + struct of_changeset cset; +}; + +static int of_overlay_apply_one(struct of_overlay *ov, + struct device_node *target, const struct device_node *overlay); + +static int of_overlay_apply_single_property(struct of_overlay *ov, + struct device_node *target, struct property *prop) +{ + struct property *propn, *tprop; + + /* NOTE: Multiple changes of single properties not supported */ + tprop = of_find_property(target, prop->name, NULL); + + /* special properties are not meant to be updated (silent NOP) */ + if (of_prop_cmp(prop->name, "name") == 0 || + of_prop_cmp(prop->name, "phandle") == 0 || + of_prop_cmp(prop->name, "linux,phandle") == 0) + return 0; + + propn = __of_prop_dup(prop, GFP_KERNEL); + if (propn == NULL) + return -ENOMEM; + + /* not found? add */ + if (tprop == NULL) + return of_changeset_add_property(&ov->cset, target, propn); + + /* found? update */ + return of_changeset_update_property(&ov->cset, target, propn); +} + +static int of_overlay_apply_single_device_node(struct of_overlay *ov, + struct device_node *target, struct device_node *child) +{ + const char *cname; + struct device_node *tchild, *grandchild; + int ret = 0; + + cname = kbasename(child->full_name); + if (cname == NULL) + return -ENOMEM; + + /* NOTE: Multiple mods of created nodes not supported */ + tchild = of_get_child_by_name(target, cname); + if (tchild != NULL) { + /* apply overlay recursively */ + ret = of_overlay_apply_one(ov, tchild, child); + of_node_put(tchild); + } else { + /* create empty tree as a target */ + tchild = __of_node_dup(child, "%s/%s", target->full_name, cname); + if (!tchild) + return -ENOMEM; + + /* point to parent */ + tchild->parent = target; + + ret = of_changeset_attach_node(&ov->cset, tchild); + if (ret) + return ret; + + ret = of_overlay_apply_one(ov, tchild, child); + if (ret) + return ret; + + /* The properties are already copied, now do the child nodes */ + for_each_child_of_node(child, grandchild) { + ret = of_overlay_apply_single_device_node(ov, tchild, grandchild); + if (ret) { + pr_err("%s: Failed to apply single node @%s/%s\n", + __func__, tchild->full_name, + grandchild->name); + return ret; + } + } + } + + return ret; +} + +/* + * Apply a single overlay node recursively. + * + * Note that the in case of an error the target node is left + * in a inconsistent state. Error recovery should be performed + * by using the changeset. + */ +static int of_overlay_apply_one(struct of_overlay *ov, + struct device_node *target, const struct device_node *overlay) +{ + struct device_node *child; + struct property *prop; + int ret; + + for_each_property_of_node(overlay, prop) { + ret = of_overlay_apply_single_property(ov, target, prop); + if (ret) { + pr_err("%s: Failed to apply prop @%s/%s\n", + __func__, target->full_name, prop->name); + return ret; + } + } + + for_each_child_of_node(overlay, child) { + ret = of_overlay_apply_single_device_node(ov, target, child); + if (ret != 0) { + pr_err("%s: Failed to apply single node @%s/%s\n", + __func__, target->full_name, + child->name); + return ret; + } + } + + return 0; +} + +/** + * of_overlay_apply() - Apply @count overlays pointed at by @ovinfo_tab + * @ov: Overlay to apply + * + * Applies the overlays given, while handling all error conditions + * appropriately. Either the operation succeeds, or if it fails the + * live tree is reverted to the state before the attempt. + * Returns 0, or an error if the overlay attempt failed. + */ +static int of_overlay_apply(struct of_overlay *ov) +{ + int i, err; + + /* first we apply the overlays atomically */ + for (i = 0; i < ov->count; i++) { + struct of_overlay_info *ovinfo = &ov->ovinfo_tab[i]; + + err = of_overlay_apply_one(ov, ovinfo->target, ovinfo->overlay); + if (err != 0) { + pr_err("%s: overlay failed '%s'\n", + __func__, ovinfo->target->full_name); + return err; + } + } + + return 0; +} + +/* + * Find the target node using a number of different strategies + * in order of preference + * + * "target" property containing the phandle of the target + * "target-path" property containing the path of the target + */ +static struct device_node *find_target_node(struct device_node *info_node) +{ + const char *path; + u32 val; + int ret; + + /* first try to go by using the target as a phandle */ + ret = of_property_read_u32(info_node, "target", &val); + if (ret == 0) + return of_find_node_by_phandle(val); + + /* now try to locate by path */ + ret = of_property_read_string(info_node, "target-path", &path); + if (ret == 0) + return of_find_node_by_path(path); + + pr_err("%s: Failed to find target for node %p (%s)\n", __func__, + info_node, info_node->name); + + return NULL; +} + +/** + * of_fill_overlay_info() - Fill an overlay info structure + * @ov Overlay to fill + * @info_node: Device node containing the overlay + * @ovinfo: Pointer to the overlay info structure to fill + * + * Fills an overlay info structure with the overlay information + * from a device node. This device node must have a target property + * which contains a phandle of the overlay target node, and an + * __overlay__ child node which has the overlay contents. + * Both ovinfo->target & ovinfo->overlay have their references taken. + * + * Returns 0 on success, or a negative error value. + */ +static int of_fill_overlay_info(struct of_overlay *ov, + struct device_node *info_node, struct of_overlay_info *ovinfo) +{ + ovinfo->overlay = of_get_child_by_name(info_node, "__overlay__"); + if (ovinfo->overlay == NULL) + goto err_fail; + + ovinfo->target = find_target_node(info_node); + if (ovinfo->target == NULL) + goto err_fail; + + return 0; + +err_fail: + of_node_put(ovinfo->target); + of_node_put(ovinfo->overlay); + + memset(ovinfo, 0, sizeof(*ovinfo)); + return -EINVAL; +} + +/** + * of_build_overlay_info() - Build an overlay info array + * @ov Overlay to build + * @tree: Device node containing all the overlays + * + * Helper function that given a tree containing overlay information, + * allocates and builds an overlay info array containing it, ready + * for use using of_overlay_apply. + * + * Returns 0 on success with the @cntp @ovinfop pointers valid, + * while on error a negative error value is returned. + */ +static int of_build_overlay_info(struct of_overlay *ov, + struct device_node *tree) +{ + struct device_node *node; + struct of_overlay_info *ovinfo; + int cnt, err; + + /* worst case; every child is a node */ + cnt = 0; + for_each_child_of_node(tree, node) + cnt++; + + ovinfo = kcalloc(cnt, sizeof(*ovinfo), GFP_KERNEL); + if (ovinfo == NULL) + return -ENOMEM; + + cnt = 0; + for_each_child_of_node(tree, node) { + memset(&ovinfo[cnt], 0, sizeof(*ovinfo)); + err = of_fill_overlay_info(ov, node, &ovinfo[cnt]); + if (err == 0) + cnt++; + } + + /* if nothing filled, return error */ + if (cnt == 0) { + kfree(ovinfo); + return -ENODEV; + } + + ov->count = cnt; + ov->ovinfo_tab = ovinfo; + + return 0; +} + +/** + * of_free_overlay_info() - Free an overlay info array + * @ov Overlay to free the overlay info from + * @ovinfo_tab: Array of overlay_info's to free + * + * Releases the memory of a previously allocated ovinfo array + * by of_build_overlay_info. + * Returns 0, or an error if the arguments are bogus. + */ +static int of_free_overlay_info(struct of_overlay *ov) +{ + struct of_overlay_info *ovinfo; + int i; + + /* do it in reverse */ + for (i = ov->count - 1; i >= 0; i--) { + ovinfo = &ov->ovinfo_tab[i]; + + of_node_put(ovinfo->target); + of_node_put(ovinfo->overlay); + } + kfree(ov->ovinfo_tab); + + return 0; +} + +static LIST_HEAD(ov_list); +static DEFINE_IDR(ov_idr); + +/** + * of_overlay_create() - Create and apply an overlay + * @tree: Device node containing all the overlays + * + * Creates and applies an overlay while also keeping track + * of the overlay in a list. This list can be used to prevent + * illegal overlay removals. + * + * Returns the id of the created overlay, or an negative error number + */ +int of_overlay_create(struct device_node *tree) +{ + struct of_overlay *ov; + int err, id; + + /* allocate the overlay structure */ + ov = kzalloc(sizeof(*ov), GFP_KERNEL); + if (ov == NULL) + return -ENOMEM; + ov->id = -1; + + INIT_LIST_HEAD(&ov->node); + + of_changeset_init(&ov->cset); + + mutex_lock(&of_mutex); + + id = idr_alloc(&ov_idr, ov, 0, 0, GFP_KERNEL); + if (id < 0) { + pr_err("%s: idr_alloc() failed for tree@%s\n", + __func__, tree->full_name); + err = id; + goto err_destroy_trans; + } + ov->id = id; + + /* build the overlay info structures */ + err = of_build_overlay_info(ov, tree); + if (err) { + pr_err("%s: of_build_overlay_info() failed for tree@%s\n", + __func__, tree->full_name); + goto err_free_idr; + } + + /* apply the overlay */ + err = of_overlay_apply(ov); + if (err) { + pr_err("%s: of_overlay_apply() failed for tree@%s\n", + __func__, tree->full_name); + goto err_abort_trans; + } + + /* apply the changeset */ + err = of_changeset_apply(&ov->cset); + if (err) { + pr_err("%s: of_changeset_apply() failed for tree@%s\n", + __func__, tree->full_name); + goto err_revert_overlay; + } + + /* add to the tail of the overlay list */ + list_add_tail(&ov->node, &ov_list); + + mutex_unlock(&of_mutex); + + return id; + +err_revert_overlay: +err_abort_trans: + of_free_overlay_info(ov); +err_free_idr: + idr_remove(&ov_idr, ov->id); +err_destroy_trans: + of_changeset_destroy(&ov->cset); + kfree(ov); + mutex_unlock(&of_mutex); + + return err; +} +EXPORT_SYMBOL_GPL(of_overlay_create); + +/* check whether the given node, lies under the given tree */ +static int overlay_subtree_check(struct device_node *tree, + struct device_node *dn) +{ + struct device_node *child; + + /* match? */ + if (tree == dn) + return 1; + + for_each_child_of_node(tree, child) { + if (overlay_subtree_check(child, dn)) + return 1; + } + + return 0; +} + +/* check whether this overlay is the topmost */ +static int overlay_is_topmost(struct of_overlay *ov, struct device_node *dn) +{ + struct of_overlay *ovt; + struct of_changeset_entry *ce; + + list_for_each_entry_reverse(ovt, &ov_list, node) { + /* if we hit ourselves, we're done */ + if (ovt == ov) + break; + + /* check against each subtree affected by this overlay */ + list_for_each_entry(ce, &ovt->cset.entries, node) { + if (overlay_subtree_check(ce->np, dn)) { + pr_err("%s: #%d clashes #%d @%s\n", + __func__, ov->id, ovt->id, + dn->full_name); + return 0; + } + } + } + + /* overlay is topmost */ + return 1; +} + +/* + * We can safely remove the overlay only if it's the top-most one. + * Newly applied overlays are inserted at the tail of the overlay list, + * so a top most overlay is the one that is closest to the tail. + * + * The topmost check is done by exploiting this property. For each + * affected device node in the log list we check if this overlay is + * the one closest to the tail. If another overlay has affected this + * device node and is closest to the tail, then removal is not permited. + */ +static int overlay_removal_is_ok(struct of_overlay *ov) +{ + struct of_changeset_entry *ce; + + list_for_each_entry(ce, &ov->cset.entries, node) { + if (!overlay_is_topmost(ov, ce->np)) { + pr_err("%s: overlay #%d is not topmost\n", + __func__, ov->id); + return 0; + } + } + + return 1; +} + +/** + * of_overlay_destroy() - Removes an overlay + * @id: Overlay id number returned by a previous call to of_overlay_create + * + * Removes an overlay if it is permissible. + * + * Returns 0 on success, or an negative error number + */ +int of_overlay_destroy(int id) +{ + struct of_overlay *ov; + int err; + + mutex_lock(&of_mutex); + + ov = idr_find(&ov_idr, id); + if (ov == NULL) { + err = -ENODEV; + pr_err("%s: Could not find overlay #%d\n", + __func__, id); + goto out; + } + + /* check whether the overlay is safe to remove */ + if (!overlay_removal_is_ok(ov)) { + err = -EBUSY; + pr_err("%s: removal check failed for overlay #%d\n", + __func__, id); + goto out; + } + + + list_del(&ov->node); + of_changeset_revert(&ov->cset); + of_free_overlay_info(ov); + idr_remove(&ov_idr, id); + of_changeset_destroy(&ov->cset); + kfree(ov); + + err = 0; + +out: + mutex_unlock(&of_mutex); + + return err; +} +EXPORT_SYMBOL_GPL(of_overlay_destroy); + +/** + * of_overlay_destroy_all() - Removes all overlays from the system + * + * Removes all overlays from the system in the correct order. + * + * Returns 0 on success, or an negative error number + */ +int of_overlay_destroy_all(void) +{ + struct of_overlay *ov, *ovn; + + mutex_lock(&of_mutex); + + /* the tail of list is guaranteed to be safe to remove */ + list_for_each_entry_safe_reverse(ov, ovn, &ov_list, node) { + list_del(&ov->node); + of_changeset_revert(&ov->cset); + of_free_overlay_info(ov); + idr_remove(&ov_idr, ov->id); + kfree(ov); + } + + mutex_unlock(&of_mutex); + + return 0; +} +EXPORT_SYMBOL_GPL(of_overlay_destroy_all); diff --git a/include/linux/of.h b/include/linux/of.h index fe1dec8..aa01cf5 100644 --- a/include/linux/of.h +++ b/include/linux/of.h @@ -23,6 +23,7 @@ #include <linux/spinlock.h> #include <linux/topology.h> #include <linux/notifier.h> +#include <linux/list.h> #include <asm/byteorder.h> #include <asm/errno.h> @@ -957,4 +958,34 @@ static inline int of_reconfig_get_state_change(unsigned long action, /* CONFIG_OF_RESOLVE api */ extern int of_resolve_phandles(struct device_node *tree); +/** + * Overlay support + */ + +#ifdef CONFIG_OF_OVERLAY + +/* ID based overlays; the API for external users */ +int of_overlay_create(struct device_node *tree); +int of_overlay_destroy(int id); +int of_overlay_destroy_all(void); + +#else + +static inline int of_overlay_create(struct device_node *tree) +{ + return -ENOTSUPP; +} + +static inline int of_overlay_destroy(int id) +{ + return -ENOTSUPP; +} + +static inline int of_overlay_destroy_all(void) +{ + return -ENOTSUPP; +} + +#endif + #endif /* _LINUX_OF_H */ |
