Changes between Initial Version and Version 1 of BuildSystemDev

Timestamp:

Mar 21, 2010, 12:57:38 AM (16 years ago)

Author:

becoulet

Comment:

--

BuildSystemDev

@@ +1 @@
+
+= Introduction =
+
+This document describes the MutekH build system configuration files and is intended for kernel developers.
+
+Be sure to first read the BuildSystem page which contains more basic information.
+
+MutekH has a component-based architecture where each module declares its configuration tokens.
+
+Tokens are declared in '''configuration description files''' which are located at various places in the MutekH source tree.
+These constraints configuration files have a different syntax from the build configuration files.
+They are designed to declare configuration tokens, express relationships between available tokens and describe associated constraints.
+
+Declared tokens may be assigned in build configuration files to build with a given configuration.
+Their values can later be tested from source code and `Makefile` files using C macros and `make` variables.
+
+= The `.config` files syntax =
+
+Their are several types of configuration tokens:
+ * normal features enabling tokens which can be either defined or undefined in build configuration files.
+ * meta tokens which can only get defined through definition of other tokens.
+ * value tokens which can have any value.
+
+== Configuration token declaration ==
+
+=== Token flags ===
+
+Several flags can be attached to tokens, most important ones are:
+ `value`::
+   Indicate the token is a value token. Value tokens can not have dependencies but can take values other than `defined` and `undefined`
+ `meta`::
+   Indicate the token is a meta token which may only be defined by an other token using the `provide` tag.
+ `auto`::
+   Indicate the token may be automatically defined to satisfy dependencies.
+
+Other flags can be attached to tokens:
+ `harddep`::
+   Indicate the token can not be safely undefined due to a unsatisfied dependency.
+ `mandatory`::
+   Indicate the token can not be undefined at all. Useful to enforce requirements on other tokens, mainly for mandatory modules.
+ `root`::
+   Indicate the token has no parent.
+ `internal`::
+   Indicate the token is for internal use and can not be defined in build configuration file directly.
+ `noexport`::
+   Indicate the token should not be written out in generated files.
+ `private`::
+   Indicate the token can not be used with `parent`, `depend` or `provide` tag from an other `.config` file.
+
+=== Constraint tags ===
+
+For each configuration token, one may use the following tags:
+ `desc Description string without quotes`::
+   Short description about the token, multiple `desc` tags will be concatenated.
+ `flags FLAGS […]`::
+   Set some flags with special meaning for the token (see above).
+ `parent TOKEN`::
+   Hierarchical dependency, it ensures all token with a parent gets silently undefined if the parent is undefined. This prevents options enabled by default to stay enabled if the parent is disabled; this way it avoids errors due to unneeded requirements. This is also used to hide irrelevant tokens from the help screen if the parent token is undefined.
+ `default value`::
+   Set the token default value. `defined` and `undefined` values act as booleans. default value is `undefined` if this line is omitted.
+ `module name [long name]`::
+   The feature token is associated with a module name. A module with the given name and the actual config file directory will be considered for building when the token gets defined.
+
+The following tags may be used to specify features constraints:
+ `depend TOKEN […]`::
+   The tag must be used to express feature dependencies, at least one of the given feature tokens is required. Unsatisfied dependency undefine the current token and emit a notice, unless flags modify this behavior.
+ `single TOKEN […]`::
+   Same as depend with the additional constraint that only one of the given tokens may be defined.
+ `exclude TOKEN`::
+   Specify excluded tokens, the current token must not be defined at the same time as any given token.
+ `when TOKEN_CONDITION […]`::
+   The current feature token will be automatically defined if all specified conditions are met. Missing dependencies will emit a notice as if it was defined in the build configuration file.
+ `provide TOKEN`::
+   Define a meta token if the current token is defined.
+
+Some tags may be used to deals with values tokens. Value tokens must have the `value` flag set:
+
+ `require TOKEN_CONDITION […]`::
+   Requirements on value tokens, having at least one condition evaluates to true on the line is mandatory if the current token is defined.
+ `provide TOKEN=value`::
+   Set a value token to the specified value if the current token is defined.
+
+Some tags can be used to give some configurations advice to the user when building MutekH:
+
+ `suggest TOKEN_CONDITION`::
+   Defining the current feature token suggest the given condition to the user.
+ `suggest_when TOKEN_CONDITION […]`::
+   The current token will be suggested to the user if dependencies are actually satisfied and all given conditions are met.
+
+The `TOKEN_CONDITION` might check different conditions:
+
+ * Token definition check: `TOKEN` or `TOKEN!`
+ * Token value equality check: `TOKEN=value`
+ * Token numerical value magnitude check: `TOKEN<value` or `TOKEN>value`
+
+The configuration tool will check both constraint rules consistency and build configuration file respect of the rules when building MutekH.
+
+Configuration constraints example:
+{{{
+%config CONFIG_FEATURE
+  desc This is a great module for MutekH
+  depend CONFIG_MUTEK_SCHEDULER
+  module great The great library
+  require CONFIG_CPU_MAXCOUNT>1
+%config end
+
+%config CONFIG_FEATURE_DEBUG
+  desc Enable debug mode for the great feature
+  parent CONFIG_FEATURE
+  provide CONFIG_FEATURE_STACK_SIZE=4096
+  when CONFIG_DEBUG
+%config end
+
+%config CONFIG_FEATURE_STACK_SIZE
+  desc This is the thread stack size for the great feature
+  parent CONFIG_FEATURE
+  flags value
+  default 512
+%config end
+
+}}}
+
+= Source tree `Makefile` syntax and rules =
+
+Makefiles in source directories may use the following variables:
+ `objs`::
+   A list of .o files compiled from `.c`, `.s` or `.S` files
+ `meta`::
+   A list of files that may be translated from `.m4`, `.cpp` or `.def` files
+ `copy`::
+   A list of files that must be copied verbatim from source directory to object directory
+ `subdirs`::
+   A list of subdirectories where more files are to be processed. These directories must exist and contain a `Makefile`.
+ `doc_headers`::
+   A list of header files which must be parsed to generate the [http://www.mutekh.org/www/mutekh_api/ MutekH API reference manual], see [wiki:HeaderDoc header documentation] for details.
+
+`Makefiles` may contain optional flags that may be used for compilation:
+ `file.o_CFLAGS=…`::
+   CFLAGS to use for a given object
+ `DIR_CFLAGS=…`::
+   CFLAGS to use for all the objects compiled by the current Makefile. Flags added by this setting add-up with the object-specific ones above.
+
+Moreover, one may use `ifeq (…,…)` make constructs to conditionally compile different things. Configuration tokens are usable.
+
+Example:
+{{{
+objs = main.o
+
+ifeq ($(CONFIG_SRL_SOCLIB),defined)
+objs += barrier.o sched_wait.o srl_log.o hw_init.o
+else
+objs += posix_wait_cycles.o
+endif
+
+main.o_CFLAGS = -O0 -ggdb
+}}}
+
+= The `arch/` and `cpu/` specific parts =
+
+Architecture and CPU directories have some special files which are injected in the building process:
+ * config.mk, included by make. It can define some compilation flags
+ * ldscript, invoked at link-time.
+  * Architecture ldscript must create a loadable binary
+  * CPU ldscript usually only specifies the entry point name
+
+== The `config.mk` file ==
+
+The arch `config.mk`  may override the following variables:
+ `ARCHCFLAGS`::
+   C-compiler flags
+ `ARCHLDFLAGS`::
+   Linker flags
+ `LD_NO_Q`::
+   Linker for the current architecture does not support -q switch, this slightly changes the linking process.
+ `HOSTCPPFLAGS`::
+   Flags to give to host's cpp (HOSTCPP) program. This is only used for expansion of `.def` files.
+
+The cpu `config.mk`  may override the following variables:
+
+ `CPUCFLAGS`::
+   C-compiler flags
+ `CPULDFLAGS`::
+   Linker flags
+
+== The `ldscript` file ==
+
+Try `info ld` for a guide through ldscripts…
+
+This ldscript is taken from architecture's object directory, thus it may be obtained from either:
+ * copy
+ * m4 processing
+ * cpp processing
+
+See
+[source:trunk/mutekh/arch/emu/ldscript arch/emu/ldscript],
+[source:trunk/mutekh/arch/soclib/ldscript.m4 arch/soclib/ldscript.m4], and
+[source:trunk/mutekh/arch/simple/ldscript.cpp arch/simple/ldscript.cpp] for the three flavors !
+
+= Notes =
+== Prerequisites ==
+
+The MutekH build-system is based on GNU Make features. It makes intensive use of:
+ * includes
+ * $(foreach) $(subst) $(eval) $(call) macros
+ * macro definitions
+Therefore, a Make-3.81 at least is mandatory.
+
+The configuration script requires perl >= 5.8.