[U-Boot] [RFC PATCH v2 1/5] env: Add support for callbacks to environment vars
Joe Hershberger
joe.hershberger at ni.com
Fri Sep 28 00:47:36 CEST 2012
Add support for callbacks to the "hashtable" functions.
One check-patch warning to inter-op with existing hashtable code:
WARNING: do not add new typedefs
+typedef struct entry ENTRY;
Signed-off-by: Joe Hershberger <joe.hershberger at ni.com>
---
Changes in v2:
- Added much-needed documentation
- Factored out prevch and nextch in env_attr_lookup()
README | 28 ++++++++
arch/arm/cpu/u-boot.lds | 7 ++
common/Makefile | 2 +
common/env_attr.c | 187 ++++++++++++++++++++++++++++++++++++++++++++++++
common/env_callback.c | 130 +++++++++++++++++++++++++++++++++
include/env_attr.h | 55 ++++++++++++++
include/env_callback.h | 72 +++++++++++++++++++
include/environment.h | 2 +
include/search.h | 5 ++
lib/hashtable.c | 65 ++++++++++++++++-
10 files changed, 552 insertions(+), 1 deletion(-)
create mode 100644 common/env_attr.c
create mode 100644 common/env_callback.c
create mode 100644 include/env_attr.h
create mode 100644 include/env_callback.h
diff --git a/README b/README
index fb9d904..47bed09 100644
--- a/README
+++ b/README
@@ -3991,6 +3991,34 @@ Please note that changes to some configuration parameters may take
only effect after the next boot (yes, that's just like Windoze :-).
+Callback functions for environment variables:
+---------------------------------------------
+
+For some environment variables, the behavior of u-boot needs to change
+when their values are changed. This functionailty allows functions to
+be associated with arbitrary variables. On creation, overwrite, or
+deletion, the callback will provide the opportunity for some side
+effect to happen or for the change to be rejected.
+
+The callbacks are named and associated with a function using the
+U_BOOT_ENV_CALLBACK macro in your board or driver code.
+
+These callbacks are associated with variables in one of two ways. The
+static list can be added to by defining CONFIG_ENV_CALLBACK_LIST_STATIC
+in the board configuration to a string that defines a list of
+associations. The list must be in the following format:
+
+ entry = variable_name[:callback_name]
+ list = entry[,list]
+
+If the callback name is not specified, then the callback is deleted.
+Spaces are also allowed anywhere in the list.
+
+Callbacks can also be associated by defining the ".callbacks" variable
+with the same list format above. Any association in ".callbacks" will
+override any association in the static list.
+
+
Command Line Parsing:
=====================
diff --git a/arch/arm/cpu/u-boot.lds b/arch/arm/cpu/u-boot.lds
index e49ca0c..5af8c36 100644
--- a/arch/arm/cpu/u-boot.lds
+++ b/arch/arm/cpu/u-boot.lds
@@ -55,6 +55,13 @@ SECTIONS
. = ALIGN(4);
+ . = .;
+ __u_boot_env_clbk_start = .;
+ .u_boot_env_clbk : { *(.u_boot_env_clbk) }
+ __u_boot_env_clbk_end = .;
+
+ . = ALIGN(4);
+
__image_copy_end = .;
.rel.dyn : {
diff --git a/common/Makefile b/common/Makefile
index 3d62775..f61c9a1 100644
--- a/common/Makefile
+++ b/common/Makefile
@@ -43,7 +43,9 @@ COBJS-y += cmd_nvedit.o
COBJS-y += cmd_version.o
# environment
+COBJS-y += env_attr.o
COBJS-y += env_common.o
+COBJS-y += env_callback.o
COBJS-$(CONFIG_ENV_IS_IN_DATAFLASH) += env_dataflash.o
COBJS-$(CONFIG_ENV_IS_IN_EEPROM) += env_eeprom.o
XCOBJS-$(CONFIG_ENV_IS_EMBEDDED) += env_embedded.o
diff --git a/common/env_attr.c b/common/env_attr.c
new file mode 100644
index 0000000..62643c8
--- /dev/null
+++ b/common/env_attr.c
@@ -0,0 +1,187 @@
+/*
+ * (C) Copyright 2012
+ * Joe Hershberger, National Instruments, joe.hershberger at ni.com
+ *
+ * See file CREDITS for list of people who contributed to this
+ * project.
+ *
+ * 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.
+ *
+ * This program is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
+ * GNU General Public License for more details.
+ *
+ * You should have received a copy of the GNU General Public License
+ * along with this program; if not, write to the Free Software
+ * Foundation, Inc., 59 Temple Place, Suite 330, Boston,
+ * MA 02111-1307 USA
+ */
+
+#include <common.h>
+#include <environment.h>
+#include <errno.h>
+#include <malloc.h>
+
+/*
+ * Iterate through the whole list calling the callback for each found element.
+ * "attr_list" takes the form:
+ * attributes = [^,:\s]*
+ * entry = name[:attributes]
+ * list = entry[,list]
+ */
+int env_attr_walk(const char *attr_list,
+ int (*callback)(const char *name, const char *attributes))
+{
+ const char *entry, *entry_end;
+ char *name, *attributes;
+
+ if (!attr_list)
+ /* list not found */
+ return 1;
+
+ entry = attr_list;
+ do {
+ char *entry_cpy = NULL;
+
+ entry_end = strchr(entry, ENV_ATTR_LIST_DELIM);
+ /* check if this is the last entry in the list */
+ if (entry_end == NULL) {
+ int entry_len = strlen(entry);
+
+ if (entry_len) {
+ /*
+ * allocate memory to copy the entry into since
+ * we will need to inject '\0' chars and squash
+ * white-space before calling the callback
+ */
+ entry_cpy = malloc(entry_len + 1);
+ if (entry_cpy)
+ /* copy the rest of the list */
+ strcpy(entry_cpy, entry);
+ else
+ return -ENOMEM;
+ }
+ } else {
+ int entry_len = entry_end - entry;
+
+ if (entry_len) {
+ /*
+ * allocate memory to copy the entry into since
+ * we will need to inject '\0' chars and squash
+ * white-space before calling the callback
+ */
+ entry_cpy = malloc(entry_len + 1);
+ if (entry_cpy) {
+ /* copy just this entry and null term */
+ strncpy(entry_cpy, entry, entry_len);
+ entry_cpy[entry_len] = '\0';
+ } else
+ return -ENOMEM;
+ }
+ }
+
+ /* check if there is anything to process (e.g. not ",,,") */
+ if (entry_cpy != NULL) {
+ attributes = strchr(entry_cpy, ENV_ATTR_SEP);
+ /* check if there is a ':' */
+ if (attributes != NULL) {
+ /* replace the ':' with '\0' to term name */
+ *attributes++ = '\0';
+ /* remove white-space from attributes */
+ attributes = strim(attributes);
+ }
+ /* remove white-space from name */
+ name = strim(entry_cpy);
+
+ /* only call the callback if there is a name */
+ if (strlen(name) != 0) {
+ int retval = 0;
+
+ retval = callback(name, attributes);
+ if (retval) {
+ free(entry_cpy);
+ return retval;
+ }
+ }
+ }
+
+ free(entry_cpy);
+ entry = entry_end + 1;
+ } while (entry_end != NULL);
+
+ return 0;
+}
+
+/*
+ * Retrieve the attributes string associated with a single name in the list
+ * There is no protection on attributes being too small for the value
+ */
+int env_attr_lookup(const char *attr_list, const char *name, char *attributes)
+{
+ const char *entry = NULL;
+
+ if (!attributes)
+ /* bad parameter */
+ return -1;
+ if (!attr_list)
+ /* list not found */
+ return 1;
+
+ entry = strstr(attr_list, name);
+ /* TODO: Search in reverse (last entry should have priority) */
+ while (entry != NULL) {
+ char prevch = *(entry - 1);
+ char nextch = *(entry + strlen(name));
+
+ /* check for an exact match */
+ if ((entry == attr_list ||
+ prevch == ENV_ATTR_LIST_DELIM ||
+ prevch == ' ') &&
+ (nextch == ENV_ATTR_SEP ||
+ nextch == ENV_ATTR_LIST_DELIM ||
+ nextch == '\0' ||
+ nextch == ' '))
+ break;
+ entry++;
+ entry = strstr(entry, name);
+ }
+ if (entry != NULL) {
+ int len;
+
+ /* skip the name */
+ entry += strlen(name);
+ /* skip spaces */
+ while (*entry == ' ')
+ entry++;
+ if (*entry != ENV_ATTR_SEP)
+ len = 0;
+ else {
+ const char *delim;
+ const char delims[2] = {ENV_ATTR_LIST_DELIM, ' '};
+
+ /* skip the attr sep */
+ entry += 1;
+ /* skip spaces */
+ while (*entry == ' ')
+ entry++;
+
+ delim = strpbrk(entry, delims);
+ if (delim == NULL)
+ len = strlen(entry);
+ else
+ len = delim - entry;
+ memcpy(attributes, entry, len);
+ }
+ attributes[len] = '\0';
+
+ /* success */
+ return 0;
+ }
+
+ /* not found in list */
+ return 2;
+}
diff --git a/common/env_callback.c b/common/env_callback.c
new file mode 100644
index 0000000..8950647
--- /dev/null
+++ b/common/env_callback.c
@@ -0,0 +1,130 @@
+/*
+ * (C) Copyright 2012
+ * Joe Hershberger, National Instruments, joe.hershberger at ni.com
+ *
+ * See file CREDITS for list of people who contributed to this
+ * project.
+ *
+ * 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.
+ *
+ * This program is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
+ * GNU General Public License for more details.
+ *
+ * You should have received a copy of the GNU General Public License
+ * along with this program; if not, write to the Free Software
+ * Foundation, Inc., 59 Temple Place, Suite 330, Boston,
+ * MA 02111-1307 USA
+ */
+
+#include <common.h>
+#include <environment.h>
+
+/*
+ * Look up a callback function pointer by name
+ */
+struct env_clbk_tbl *find_env_callback(const char *name)
+{
+ struct env_clbk_tbl *clbkp;
+
+ if (name == NULL)
+ return NULL;
+
+ /* look up the callback in the linker-list */
+ /* TODO: replace with generic linker-list from marex */
+ for (clbkp = &__u_boot_env_clbk_start;
+ clbkp != &__u_boot_env_clbk_end;
+ clbkp++) {
+ if (strcmp(name, clbkp->name) == 0)
+ return clbkp;
+ }
+
+ return NULL;
+}
+
+/*
+ * Look for a possible callback for a newly added variable
+ * This is called specifically when the variable did not exist in the hash
+ * previously, so the blanket update did not find this variable.
+ */
+void env_callback_bind(ENTRY *var_entry)
+{
+ const char *var_name = var_entry->key;
+ const char *callback_list = getenv(ENV_CALLBACK_VAR);
+ char callback_name[256] = "";
+ struct env_clbk_tbl *clbkp;
+ int ret = 1;
+
+ /* look in the ".callbacks" var for a reference to this variable */
+ if (callback_list != NULL)
+ ret = env_attr_lookup(callback_list, var_name, callback_name);
+
+ /* only if not found there, look in the static list */
+ if (ret)
+ ret = env_attr_lookup(ENV_CALLBACK_LIST_STATIC, var_name,
+ callback_name);
+
+ /* if an association was found, set the callback pointer */
+ if (!ret && strlen(callback_name)) {
+ clbkp = find_env_callback(callback_name);
+ if (clbkp != NULL)
+ var_entry->callback = clbkp->callback;
+ }
+}
+
+/*
+ * Called on each existing env var prior to the blanket update since removing
+ * a callback association should remove its callback.
+ */
+static int clear_callback(ENTRY *entry)
+{
+ entry->callback = NULL;
+
+ return 0;
+}
+
+/*
+ * Call for each element in the list that associates variables to callbacks
+ */
+static int set_callback(const char *name, const char *value)
+{
+ ENTRY e, *ep;
+ struct env_clbk_tbl *clbkp;
+
+ e.key = name;
+ e.data = NULL;
+ hsearch_r(e, FIND, &ep, &env_htab);
+
+ /* does the env variable actually exist? */
+ if (ep != NULL) {
+ /* the assocaition delares no callback, so remove the pointer */
+ if (value == NULL || strlen(value) == 0)
+ ep->callback = NULL;
+ else {
+ /* assign the requested callback */
+ clbkp = find_env_callback(value);
+ if (clbkp != NULL)
+ ep->callback = clbkp->callback;
+ }
+ }
+
+ return 0;
+}
+
+static int on_callbacks(const char *name, const char *value, enum env_op op)
+{
+ /* remove all callbacks */
+ hwalk_r(&env_htab, clear_callback);
+
+ /* configure any static callback bindings */
+ env_attr_walk(ENV_CALLBACK_LIST_STATIC, set_callback);
+ /* configure any dynamic callback bindings */
+ env_attr_walk(value, set_callback);
+
+ return 0;
+}
+U_BOOT_ENV_CALLBACK(callbacks, on_callbacks);
diff --git a/include/env_attr.h b/include/env_attr.h
new file mode 100644
index 0000000..6ef114f
--- /dev/null
+++ b/include/env_attr.h
@@ -0,0 +1,55 @@
+/*
+ * (C) Copyright 2012
+ * Joe Hershberger, National Instruments, joe.hershberger at ni.com
+ *
+ * See file CREDITS for list of people who contributed to this
+ * project.
+ *
+ * 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.
+ *
+ * This program is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
+ * GNU General Public License for more details.
+ *
+ * You should have received a copy of the GNU General Public License
+ * along with this program; if not, write to the Free Software
+ * Foundation, Inc., 59 Temple Place, Suite 330, Boston,
+ * MA 02111-1307 USA
+ */
+
+#ifndef __ENV_ATTR_H__
+#define __ENV_ATTR_H__
+
+#define ENV_ATTR_LIST_DELIM ','
+#define ENV_ATTR_SEP ':'
+
+/*
+ * env_attr_walk takes as input an "attr_list" that takes the form:
+ * attributes = [^,:\s]*
+ * entry = name[:attributes]
+ * list = entry[,list]
+ * It will call the "callback" function with the "name" and attribute as "value"
+ * The callback may return a non-0 to abort the list walk.
+ * This return value will be passed through to the caller.
+ * 0 is returned on success.
+ */
+extern int env_attr_walk(const char *attr_list,
+ int (*callback)(const char *name, const char *value));
+
+/*
+ * env_attr_lookup takes as input an "attr_list" with the same form as above.
+ * It also takes as input a "name" to look for.
+ * If the name is found in the list, it's value is copied into "attributes".
+ * There is no protection on attributes being too small for the value.
+ * It returns -1 if attributes is NULL, 1 if "name" is not found, 2 if
+ * "attr_list" is NULL.
+ * Returns 0 on success.
+ */
+extern int env_attr_lookup(const char *attr_list, const char *name,
+ char *attributes);
+
+#endif /* __ENV_ATTR_H__ */
diff --git a/include/env_callback.h b/include/env_callback.h
new file mode 100644
index 0000000..76ac865
--- /dev/null
+++ b/include/env_callback.h
@@ -0,0 +1,72 @@
+/*
+ * (C) Copyright 2012
+ * Joe Hershberger, National Instruments, joe.hershberger at ni.com
+ *
+ * See file CREDITS for list of people who contributed to this
+ * project.
+ *
+ * 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.
+ *
+ * This program is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
+ * GNU General Public License for more details.
+ *
+ * You should have received a copy of the GNU General Public License
+ * along with this program; if not, write to the Free Software
+ * Foundation, Inc., 59 Temple Place, Suite 330, Boston,
+ * MA 02111-1307 USA
+ */
+
+#ifndef __ENV_CALLBACK_H__
+#define __ENV_CALLBACK_H__
+
+#define ENV_CALLBACK_VAR ".callbacks"
+
+/* Board configs can define additional static callback bindings */
+#ifndef CONFIG_ENV_CALLBACK_LIST_STATIC
+#define CONFIG_ENV_CALLBACK_LIST_STATIC
+#endif
+
+/*
+ * This list of callback bindings is static, but may be overridden by defining
+ * a new assogiation in the ".callbacks" environment variable.
+ */
+#define ENV_CALLBACK_LIST_STATIC ENV_CALLBACK_VAR ":callbacks," \
+ CONFIG_ENV_CALLBACK_LIST_STATIC
+
+enum env_op {
+ env_op_none,
+ env_op_create,
+ env_op_delete,
+ env_op_overwrite,
+};
+
+struct env_clbk_tbl {
+ const char *name; /* Callback name */
+ int (*callback)(const char *name, const char *value, enum env_op op);
+};
+
+extern struct env_clbk_tbl __u_boot_env_clbk_start;
+extern struct env_clbk_tbl __u_boot_env_clbk_end;
+
+struct env_clbk_tbl *find_env_callback(const char *);
+typedef struct entry ENTRY;
+void env_callback_bind(ENTRY *var_entry);
+
+#define ENV_CLBK_SECTION __attribute__((unused, section(".u_boot_env_clbk"), \
+ aligned(4)))
+
+/*
+ * Define a callback that can be associated with variables.
+ * when associated through the ".callbacks" environment variable, the callback
+ * will be executed any time the variable is inserted, overwritten, or deleted.
+ */
+#define U_BOOT_ENV_CALLBACK(name, callback) \
+ struct env_clbk_tbl __u_boot_env_clbk_##name ENV_CLBK_SECTION = \
+ {#name, callback}
+
+#endif /* __ENV_CALLBACK_H__ */
diff --git a/include/environment.h b/include/environment.h
index ae3f7b6..040352f 100644
--- a/include/environment.h
+++ b/include/environment.h
@@ -164,6 +164,8 @@ extern void env_reloc(void);
#ifndef DO_DEPS_ONLY
+#include <env_attr.h>
+#include <env_callback.h>
#include <search.h>
extern struct hsearch_data env_htab;
diff --git a/include/search.h b/include/search.h
index ef53edb..9d0d498 100644
--- a/include/search.h
+++ b/include/search.h
@@ -29,6 +29,7 @@
#define _SEARCH_H 1
#include <stddef.h>
+#include <env_callback.h>
#define __set_errno(val) do { errno = val; } while (0)
@@ -41,6 +42,7 @@ typedef enum {
typedef struct entry {
const char *key;
char *data;
+ int (*callback)(const char *name, const char *value, enum env_op op);
} ENTRY;
/* Opaque type for internal use. */
@@ -98,6 +100,9 @@ extern int himport_r(struct hsearch_data *__htab,
const char *__env, size_t __size, const char __sep,
int __flag);
+/* Walk the whole table calling the callback on each element */
+extern int hwalk_r(struct hsearch_data *__htab, int (*callback)(ENTRY *));
+
/* Flags for himport_r() */
#define H_NOCLEAR 1 /* do not clear hash table before importing */
diff --git a/lib/hashtable.c b/lib/hashtable.c
index abd61c8..22ff617 100644
--- a/lib/hashtable.c
+++ b/lib/hashtable.c
@@ -54,7 +54,8 @@
#define CONFIG_ENV_MAX_ENTRIES 512
#endif
-#include "search.h"
+#include <env_callback.h>
+#include <search.h>
/*
* [Aho,Sethi,Ullman] Compilers: Principles, Techniques and Tools, 1986
@@ -290,6 +291,15 @@ int hsearch_r(ENTRY item, ACTION action, ENTRY ** retval,
&& strcmp(item.key, htab->table[idx].entry.key) == 0) {
/* Overwrite existing value? */
if ((action == ENTER) && (item.data != NULL)) {
+ /* If there is a callback, call it */
+ if (htab->table[idx].entry.callback &&
+ htab->table[idx].entry.callback(
+ item.key, item.data, env_op_overwrite)) {
+ __set_errno(EINVAL);
+ *retval = NULL;
+ return 0;
+ }
+
free(htab->table[idx].entry.data);
htab->table[idx].entry.data =
strdup(item.data);
@@ -332,6 +342,16 @@ int hsearch_r(ENTRY item, ACTION action, ENTRY ** retval,
&& strcmp(item.key, htab->table[idx].entry.key) == 0) {
/* Overwrite existing value? */
if ((action == ENTER) && (item.data != NULL)) {
+ /* If there is a callback, call it */
+ if (htab->table[idx].entry.callback &&
+ htab->table[idx].entry.callback(
+ item.key, item.data,
+ env_op_overwrite)) {
+ __set_errno(EINVAL);
+ *retval = NULL;
+ return 0;
+ }
+
free(htab->table[idx].entry.data);
htab->table[idx].entry.data =
strdup(item.data);
@@ -380,6 +400,18 @@ int hsearch_r(ENTRY item, ACTION action, ENTRY ** retval,
++htab->filled;
+ /* This is a new entry, so look up a possible callback */
+ env_callback_bind(&htab->table[idx].entry);
+
+ /* If there is a callback, call it */
+ if (htab->table[idx].entry.callback &&
+ htab->table[idx].entry.callback(item.key, item.data,
+ env_op_create)) {
+ __set_errno(EINVAL);
+ *retval = NULL;
+ return 0;
+ }
+
/* return new entry */
*retval = &htab->table[idx].entry;
return 1;
@@ -415,6 +447,13 @@ int hdelete_r(const char *key, struct hsearch_data *htab)
return 0; /* not found */
}
+ /* If there is a callback, call it */
+ if (htab->table[idx].entry.callback &&
+ htab->table[idx].entry.callback(key, NULL, env_op_delete)) {
+ __set_errno(EINVAL);
+ return 0;
+ }
+
/* free used ENTRY */
debug("hdelete: DELETING key \"%s\"\n", key);
@@ -765,3 +804,27 @@ int himport_r(struct hsearch_data *htab,
debug("INSERT: done\n");
return 1; /* everything OK */
}
+
+/*
+ * hwalk_r()
+ */
+
+/*
+ * Walk all of the entries in the hash, calling the callback for each one.
+ * this allows some generic operation to be performed on each element.
+ */
+int hwalk_r(struct hsearch_data *htab, int (*callback)(ENTRY *))
+{
+ int i;
+ int retval;
+
+ for (i = 1; i <= htab->size; ++i) {
+ if (htab->table[i].used > 0) {
+ retval = callback(&htab->table[i].entry);
+ if (retval)
+ return retval;
+ }
+ }
+
+ return 0;
+}
--
1.7.11.5
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