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authorzwelch <zwelch@b42882b7-edfa-0310-969c-e2dbd0fdcd60>2009-05-20 08:48:19 +0000
committerzwelch <zwelch@b42882b7-edfa-0310-969c-e2dbd0fdcd60>2009-05-20 08:48:19 +0000
commitc46dc5ba2dd1e21fd1936421114cfeac6d9d2cfb (patch)
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Move TCL overview from source tree to doxygen manual.
git-svn-id: svn://svn.berlios.de/openocd/trunk@1855 b42882b7-edfa-0310-969c-e2dbd0fdcd60
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-****************************************
-****************************************
-
-This is a short introduction to 'un-scare' you about the language
-known as TCL. It is structured as a guided tour through the files
-written by me [Duane Ellis] - in early July 2008 for OpenOCD.
-
-Which uses the "JIM" embedded Tcl clone-ish language.
-
-Thing described here are *totally* TCL generic... not Jim specific.
-
-The goal of this document is to encourage you to add your own set of
-chips to the TCL package - and most importantly you should know where
-you should put them - so they end up in an organized way.
-
---Duane Ellis.
- duane@duaneellis.com
-
-****************************************
-****************************************
-
-Adding "chip" support - Duane Ellis July 5 - 2008.
-
-The concept is this:
- In your "openocd.cfg" file add something like this:
-
- source [find tcl/chip/VENDOR/FAMILY/NAME.tcl]
-
- For example...
- source [find tcl/chip/atmel/at91/at91sam7x256.tcl]
-
- You'll notice that it makes use of:
-
- tcl/cpu/arm/<NAME>.tcl.
-
- Yes, that is where you should put "core" specific things.
- Be careful and learn the difference:
-
- THE "CORE" - is not the entire chip!
-
-Definition:
- That "file" listed above is called a "CHIP FILE".
-
- It may be standalone, or may need to "source" other "helper" files.
-
- The reference [7/5/2008] is the at91sam7x256.tcl file.
-
-****************************************
-****************************************
-=== TCL TOUR ===
-Open: at91sam7x256.tcl
-=== TCL TOUR ===
-
-A walk through --- For those who are new to TCL.
-
-Examine the file: at91sam7x256.tcl
-
-It starts with:
- source [find path/filename.tcl]
-
-In TCL - this is very important.
-
- Rule #1 Everything is a string.
- Rule #2 If you think other wise See #1.
-Reminds you of:
- Rule #1: The wife is correct.
- Rule #2: If you think otherwise, See #1
-
-Any text contained inside of [square-brackets]
-is just like `back-ticks` in BASH.
-
-Hence, the [find FILENAME] executes the command find with a single
-parameter the filename.
-
-========================================
-
-Next you see a series of:
-
-set NAME VALUE
-
-It is mostly "obvious" what is going on.
-
-Exception: The arrays.
-
- You would *THINK* Tcl supports arrays.
- In fact, multi-dim arrays. That is false.
-
- For the index for"FLASH(0,CHIPSELECT)" is actually the string
- "0,CHIPSELECT". This is problematic. In the normal world, you think
- of array indexes as integers.
-
- For example these are different:
-
- set foo(0x0c) 123
- set foo(12) 444
-
- Why? Because 0x0c {lowercase} is a string.
- Don't forget UPPER CASE.
-
- You must be careful - always... always... use simple decimal
- numbers. When in doubt use 'expr' the evaluator. These are all the
- same.
-
- set x 0x0c
- set foo([expr $x]) "twelve"
-
- set x 12
- set foo([expr $x]) "twelve"
-
- set x "2 * 6"
- set foo([expr $x]) "twelve"
-
-**************************************************
-***************************************************
-=== TCL TOUR ===
-Open the file: "bitsbytes.tcl"
-
-There is some tricky things going on.
-===============
-
-First, there is a "for" loop - at level 0
-{level 0 means: out side of a proc/function}
-
-This means it is evaluated when the file is parsed.
-
-== SIDEBAR: About The FOR command ==
-In TCL, "FOR" is a funny thing, it is not what you think it is.
-
-Syntactically - FOR is a just a command, it is not language
-construct like for(;;) in C...
-
-The "for" command takes 4 parameters.
- (1) The "initial command" to execute.
- (2) the test "expression"
- (3) the "next command"
- (4) the "body command" of the FOR loop.
-
-Notice I used the words "command" and "expression" above.
-
-The FOR command:
-1) executes the "initial command"
-2) evaluates the expression if 0 it stops.
-3) executes the "body command"
-4) executes the "next command"
-5) Goto Step 2.
-
-As show, each of these items are in {curly-braces}. This means they
-are passed as they are - KEY-POINT: un evaluated to the FOR
-command. Think of it like escaping the backticks in Bash so that the
-"under-lying" command can evaluate the contents. In this case, the FOR
-COMMAND.
-
-== END: SIDEBAR: About The FOR command ==
-
-You'll see two lines:
-
-LINE1:
- set vn [format "BIT%d" $x]
-
-Format is like "sprintf". Because of the [brackets], it becomes what
-you think. But here's how:
-
-First - the line is parsed - for {braces}. In this case, there are
-none. The, the parser looks for [brackets] and finds them. The,
-parser then evaluates the contents of the [brackets], and replaces
-them. It is alot this bash statement.
-
- EXPORT vn=`date`
-
-LINE 2 & 3
- set $vn [expr (1024 * $x)]
- global $vn
-
-In line 1, we dynamically created a variable name. Here, we are
-assigning it a value. Lastly Line 3 we force the variable to be
-global, not "local" the the "for command body"
-
-===============
-The PROCS
-
-proc create_mask { MSB LSB } {
- ... body ....
-}
-
-Like "for" - PROC is really just a command that takes 3 parameters.
-The (1) NAME of the function, a (2) LIST of parameters, and a (3) BODY
-
-Again, this is at "level 0" so it is a global function. (Yes, TCL
-supports local functions, you put them inside of a function}
-
-You'll see in some cases, I nest [brackets] alot and in others I'm
-lazy or wanted it to be more clear... it is a matter of choice.
-===============
-
-
-**************************************************
-***************************************************
-=== TCL TOUR ===
-Open the file: "memory.tcl"
-===============
-
-Here is where I setup some 'memory definitions' that various targets can use.
-
-For example - there is an "unknown" memory region.
-
-All memory regions must have 2 things:
-
- (1) N_<name>
- (2) NAME( array )
- And the array must have some specific names:
- ( <idx>, THING )
- Where: THING is one of:
- CHIPSELECT
- BASE
- LEN
- HUMAN
- TYPE
- RWX - the access ability.
- WIDTH - the accessible width.
-
- ie: Some regions of memory are not 'word'
- accessible.
-
-The function "address_info" - given an address should
-tell you about the address.
-
- [as of this writing: 7/5/2008 I have done
- only a little bit with this -Duane]
-
-===
-MAJOR FUNCTION:
-==
-
-proc memread32 { ADDR }
-proc memread16 { ADDR }
-proc memread8 { ADDR }
-
-All read memory - and return the contents.
-
-[ FIXME: 7/5/2008 - I need to create "memwrite" functions]
-
-**************************************************
-***************************************************
-=== TCL TOUR ===
-Open the file: "mmr_helpers.tcl"
-===============
-
-This file is used to display and work with "memory mapped registers"
-
-For example - 'show_mmr32_reg' is given the NAME of the register to
-display. The assumption is - the NAME is a global variable holding the
-address of that MMR.
-
-The code does some tricks. The [set [set NAME]] is the TCL way
-of doing double variable interpolation - like makefiles...
-
-In a makefile or shell script you may have seen this:
-
- FOO_linux = "Penguins rule"
- FOO_winXP = "Broken Glass"
- FOO_mac = "I like cat names"
-
- # Pick one
- BUILD = linux
- #BUILD = winXP
- #BUILD = mac
- FOO = ${FOO_${BUILD}}
-
-The "double [set] square bracket" thing is the TCL way, nothing more.
-
-----
-
-The IF statement - and "CATCH" .
-
-Notice this IF COMMAND - (not statement) is like this:
-[7/5/2008 it is this way]
-
- if ![catch { command } msg ] {
- ...something...
- } else {
- error [format string...]
- }
-
-The "IF" command expects either 2 params, or 4 params.
-
- === Sidebar: About "commands" ===
-
- Take a look at the internals of "jim.c"
- Look for the function: Jim_IfCoreCommand()
- And all those other "CoreCommands"
-
- You'll notice - they all have "argc" and "argv"
-
- Yea, the entire thing is done that way.
-
- IF is a command. SO is "FOR" and "WHILE" and "DO" and the
- others. That is why I keep using the phase it is a "command"
-
- === END: Sidebar: About "commands" ===
-
-Parameter 1 to the IF command is expected to be an expression.
-
-As such, I do not need to wrap it in {braces}.
-
-In this case, the "expression" is the result of the "CATCH" command.
-
-CATCH - is an error catcher.
-
-You give CATCH 1 or 2 parameters.
- The first 1st parameter is the "code to execute"
- The 2nd (optional) is where to put the error message.
-
- CATCH returns 0 on success, 1 for failure.
- The "![catch command]" is self explaintory.
-
-
-The 3rd parameter to IF must be exactly "else" or "elseif" [I lied
-above, the IF command can take many parameters they just have to
-be joined by exactly the words "else" or "elseif".
-
-The 4th parameter contains:
-
- "error [format STRING....]"
-
-This lets me modify the previous lower level error by tacking more
-text onto the end of it. In this case, i want to add the MMR register
-name to make my error message look better.
-
----------
-Back to something inside show_mmr32_reg{}.
-
-You'll see something 'set fn show_${NAME}_helper' Here I am
-constructing a 'function name' Then - I look it up to see if it
-exists. {the function: "proc_exists" does this}
-
-And - if it does - I call the function.
-
-In "C" it is alot like using: 'sprintf()' to construct a function name
-string, then using "dlopen()" and "dlsym()" to look it up - and get a
-function pointer - and calling the function pointer.
-
-In this case - I execute a dynamic command. You can do some cool
-tricks with interpretors.
-
-----------
-
-Function: show_mmr32_bits()
-
-In this case, we use the special TCL command "upvar" which tcl's way
-of passing things by reference. In this case, we want to reach up into
-the callers lexical scope and find the array named "NAMES"
-
-The rest of the function is pretty straight forward.
-
-First - we figure out the longest name.
-Then print 4 rows of 8bits - with names.
-
-
-**************************************************
-***************************************************
-=== TCL TOUR ===
-Open the file: "chips/atmel/at91/usarts.tcl"
-===============
-
-First - about the AT91SAM series - all of the usarts
-are basically identical...
-
-Second - there can be many of them.
-
-In this case - I do some more TCL tricks to dynamically
-create functions out of thin air.
-
-Some assumptions:
-
-The "CHIP" file has defined some variables in a proper form.
-
-ie: AT91C_BASE_US0 - for usart0,
- AT91C_BASE_US1 - for usart1
- ... And so on ...
-
-Near the end of the file - look for a large "foreach" loop that
-looks like this:
-
- foreach WHO { US0 US1 US2 US3 US4 .... } {
-
- }
-
-In this case, I'm trying to figure out what USARTs exist.
-
-Step 1 - is to determine if the NAME has been defined.
-ie: Does AT91C_BASE_USx - where X is some number exist?
-
-The "info exists VARNAME" tells you if the variable exists. Then -
-inside the IF statement... There is another loop. This loop is the
-name of various "sub-registers" within the USART.
-
-Some more trick are played with the [set VAR] backtick evaluation stuff.
-And we create two variables
-
-We calculate and create the global variable name for every subregister in the USART.
-And - declare that variable as GLOBAL so the world can find it.
-
-Then - we dynamically create a function - based on the register name.
-
-Look carefully at how that is done. You'll notice the FUNCTION BODY is
-a string - not something in {braces}. Why? This is because we need TCL
-to evaluate the contents of that string "*NOW*" - when $vn exists not
-later, when the function "show_FOO" is invoked.
-
-Lastly - we build a "str" of commands - and create a single function -
-with the generated list of commands for the entire USART.
-
-With that little bit of code - I now have a bunch of functions like:
-
- show_US0, show_US1, show_US2, .... etc ...
-
- And show_US0_MR, show_US0_IMR ... etc...
-
-And - I have this for every USART... without having to create tons of
-boiler plate yucky code.
-
-****************************************
-****************************************
-END of the Tcl Intro and Walk Through
-****************************************
-****************************************
-
-FUTURE PLANS
-
- Some "GPIO" functions...