path: root/lib
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authorWolfgang Denk <wd@denx.de>2010-06-20 23:33:59 +0200
committerWolfgang Denk <wd@denx.de>2010-09-19 19:29:48 +0200
commitea882baf9c17cd142c99e3ff640d3ab01daa5cec (patch)
treeedf6a32f670aa9a54572e142f22070ef6d636e4f /lib
parent91a76751a090bf43c166fda0815c9b5b2bfccbe9 (diff)
New implementation for internal handling of environment variables.
Motivation: * Old environment code used a pessimizing implementation: - variable lookup used linear search => slow - changed/added variables were added at the end, i. e. most frequently used variables had the slowest access times => slow - each setenv() would calculate the CRC32 checksum over the whole environment block => slow * "redundant" envrionment was locked down to two copies * No easy way to implement features like "reset to factory defaults", or to select one out of several pre-defined (previously saved) sets of environment settings ("profiles") * No easy way to import or export environment settings ====================================================================== API Changes: - Variable names starting with '#' are no longer allowed I didn't find any such variable names being used; it is highly recommended to follow standard conventions and start variable names with an alphanumeric character - "printenv" will now print a backslash at the end of all but the last lines of a multi-line variable value. Multi-line variables have never been formally defined, allthough there is no reason not to use them. Now we define rules how to deal with them, allowing for import and export. - Function forceenv() and the related code in saveenv() was removed. At the moment this is causing build problems for the only user of this code (schmoogie - which has no entry in MAINTAINERS); may be fixed later by implementing the "env set -f" feature. Inconsistencies: - "printenv" will '\\'-escape the '\n' in multi-line variables, while "printenv var" will not do that. ====================================================================== Advantages: - "printenv" output much better readable (sorted) - faster! - extendable (additional variable properties can be added) - new, powerful features like "factory reset" or easy switching between several different environment settings ("profiles") Disadvantages: - Image size grows by typically 5...7 KiB (might shrink a bit again on systems with redundant environment with a following patch series) ====================================================================== Implemented: - env command with subcommands: - env print [arg ...] same as "printenv": print environment - env set [-f] name [arg ...] same as "setenv": set (and delete) environment variables ["-f" - force setting even for read-only variables - not implemented yet.] - end delete [-f] name not implemented yet ["-f" - force delete even for read-only variables] - env save same as "saveenv": save environment - env export [-t | -b | -c] addr [size] export internal representation (hash table) in formats usable for persistent storage or processing: -t: export as text format; if size is given, data will be padded with '\0' bytes; if not, one terminating '\0' will be added (which is included in the "filesize" setting so you can for exmple copy this to flash and keep the termination). -b: export as binary format (name=value pairs separated by '\0', list end marked by double "\0\0") -c: export as checksum protected environment format as used for example by "saveenv" command addr: memory address where environment gets stored size: size of output buffer With "-c" and size is NOT given, then the export command will format the data as currently used for the persistent storage, i. e. it will use CONFIG_ENV_SECT_SIZE as output block size and prepend a valid CRC32 checksum and, in case of resundant environment, a "current" redundancy flag. If size is given, this value will be used instead of CONFIG_ENV_SECT_SIZE; again, CRC32 checksum and redundancy flag will be inserted. With "-b" and "-t", always only the real data (including a terminating '\0' byte) will be written; here the optional size argument will be used to make sure not to overflow the user provided buffer; the command will abort if the size is not sufficient. Any remainign space will be '\0' padded. On successful return, the variable "filesize" will be set. Note that filesize includes the trailing/terminating '\0' byte(s). Usage szenario: create a text snapshot/backup of the current settings: => env export -t 100000 => era ${backup_addr} +${filesize} => cp.b 100000 ${backup_addr} ${filesize} Re-import this snapshot, deleting all other settings: => env import -d -t ${backup_addr} - env import [-d] [-t | -b | -c] addr [size] import external format (text or binary) into hash table, optionally deleting existing values: -d: delete existing environment before importing; otherwise overwrite / append to existion definitions -t: assume text format; either "size" must be given or the text data must be '\0' terminated -b: assume binary format ('\0' separated, "\0\0" terminated) -c: assume checksum protected environment format addr: memory address to read from size: length of input data; if missing, proper '\0' termination is mandatory - env default -f reset default environment: drop all environment settings and load default environment - env ask name [message] [size] same as "askenv": ask for environment variable - env edit name same as "editenv": edit environment variable - env run same as "run": run commands in an environment variable ====================================================================== TODO: - drop default env as implemented now; provide a text file based initialization instead (eventually using several text files to incrementally build it from common blocks) and a tool to convert it into a binary blob / object file. - It would be nice if we could add wildcard support for environment variables; this is needed for variable name auto-completion, but it would also be nice to be able to say "printenv ip*" or "printenv *addr*" - Some boards don't link any more due to the grown code size: DU405, canyonlands, sequoia, socrates. => cc: Matthias Fuchs <matthias.fuchs@esd-electronics.com>, Stefan Roese <sr@denx.de>, Heiko Schocher <hs@denx.de> - Dropping forceenv() causes build problems on schmoogie => cc: Sergey Kubushyn <ksi@koi8.net> - Build tested on PPC and ARM only; runtime tested with NOR and NAND flash only => needs testing!! Signed-off-by: Wolfgang Denk <wd@denx.de> Cc: Matthias Fuchs <matthias.fuchs@esd-electronics.com>, Cc: Stefan Roese <sr@denx.de>, Cc: Heiko Schocher <hs@denx.de> Cc: Sergey Kubushyn <ksi@koi8.net>
Diffstat (limited to 'lib')
1 files changed, 23 insertions, 9 deletions
diff --git a/lib/hashtable.c b/lib/hashtable.c
index 2f3b5c8d1..b747f1f79 100644
--- a/lib/hashtable.c
+++ b/lib/hashtable.c
@@ -45,6 +45,10 @@
# include <linux/string.h>
+#ifndef CONFIG_ENV_MAX_ENTRIES /* maximum number of entries */
#include "search.h"
@@ -636,15 +640,23 @@ int himport_r(struct hsearch_data *htab,
* table size is based on heuristics: in a sample of some 70+
* existing systems we found an average size of 39+ bytes per entry
* in the environment (for the whole key=value pair). Assuming a
- * size of 7 per entry (= safety factor of >5) should provide enough
- * safety margin for any existing environment definitons and still
+ * size of 8 per entry (= safety factor of ~5) should provide enough
+ * safety margin for any existing environment definitions and still
* allow for more than enough dynamic additions. Note that the
* "size" argument is supposed to give the maximum enviroment size
+ * (CONFIG_ENV_SIZE). This heuristics will result in
+ * unreasonably large numbers (and thus memory footprint) for
+ * big flash environments (>8,000 entries for 64 KB
+ * envrionment size), so we clip it to a reasonable value
+ * (which can be overwritten in the board config file if
+ * needed).
if (!htab->table) {
- int nent = size / 7;
+ int nent = size / 8;
debug("Create Hash Table: N=%d\n", nent);
@@ -705,17 +717,19 @@ int himport_r(struct hsearch_data *htab,
hsearch_r(e, ENTER, &rv, htab);
if (rv == NULL) {
- printf("himport_r: can't insert \"%s=%s\" into hash table\n", name, value);
+ printf("himport_r: can't insert \"%s=%s\" into hash table\n",
+ name, value);
return 0;
- debug("INSERT: %p ==> name=\"%s\" value=\"%s\"\n", rv, name,
- value);
- debug(" table = %p, size = %d, filled = %d\n", htab,
- htab->size, htab->filled);
+ debug("INSERT: table %p, filled %d/%d rv %p ==> name=\"%s\" value=\"%s\"\n",
+ htab, htab->filled, htab->size,
+ rv, name, value);
} while ((dp < data + size) && *dp); /* size check needed for text */
/* without '\0' termination */
+ debug("INSERT: free(data = %p)\n", data);
+ debug("INSERT: done\n");
return 1; /* everything OK */