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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>
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This implementation is based on code from uClibc-0.9.30.3 but was
modified and extended for use within U-Boot.
Major modifications and extensions:
* hsearch() [modified / extended]:
- While the standard version does not make any assumptions about
the type of the stored data objects at all, this implementation
works with NUL terminated strings only.
- Instead of storing just pointers to the original objects, we
create local copies so the caller does not need to care about the
data any more.
- The standard implementation does not provide a way to update an
existing entry. This version will create a new entry or update an
existing one when both "action == ENTER" and "item.data != NULL".
- hsearch_r(): Instead of returning 1 on success, we return the
index into the internal hash table, which is also guaranteed to be
positive. This allows us direct access to the found hash table
slot for example for functions like hdelete().
* hdelete() [added]:
- The standard implementation of hsearch(3) does not provide any way
to delete any entries from the hash table. We extend the code to
do that.
* hexport() [added]:
- Export the data stored in the hash table in linearized form:
Entries are exported as "name=value" strings, separated by an
arbitrary (non-NUL, of course) separator character. This allows to
use this function both when formatting the U-Boot environment for
external storage (using '\0' as separator), but also when using it
for the "printenv" command to print all variables, simply by using
as '\n" as separator. This can also be used for new features like
exporting the environment data as text file, including the option
for later re-import.
- The entries in the result list will be sorted by ascending key
values.
* himport() [added]:
- Import linearized data into hash table. This is the inverse
function to hexport(): it takes a linear list of "name=value"
pairs and creates hash table entries from it.
- Entries without "value", i. e. consisting of only "name" or
"name=", will cause this entry to be deleted from the hash table.
- The "flag" argument can be used to control the behaviour: when
the H_NOCLEAR bit is set, then an existing hash table will kept,
i. e. new data will be added to an existing hash table;
otherwise, old data will be discarded and a new hash table will
be created.
- The separator character for the "name=value" pairs can be
selected, so we both support importing from externally stored
environment data (separated by NUL characters) and from plain text
files (entries separated by newline characters).
- To allow for nicely formatted text input, leading white space
(sequences of SPACE and TAB chars) is ignored, and entries
starting (after removal of any leading white space) with a '#'
character are considered comments and ignored.
- NOTE: this means that a variable name cannot start with a '#'
character.
- When using a non-NUL separator character, backslash is used as
escape character in the value part, allowing for example fo
multi-line values.
- In theory, arbitrary separator characters can be used, but only
'\0' and '\n' have really been tested.
Signed-off-by: Wolfgang Denk <wd@denx.de>
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