readme.makerules

一个linux下rs485驱动程序的源代码

Description of OCERA Make System for CAN Components (OMK)
=========================================================

Important notice:
This make system uses features found in recent versions of GNU Make
program. If you encounter problems with package building,
check, that you use correct version of Make program.
The Make older than version 3.80, could not be used.
Even Make version 3.80 has annoying bug which causes
building fail with misleading message "virtual memory exhausted".
Please, upgrade to last version of Make (3.81beta1).
You can take it from GNU CVS or from our local copy

http://cmp.felk.cvut.cz/~pisa/can/make-3.81beta1.tar.gz


There is list of features which we want to solve with our makesystem:
 - central Makefile.rules for most of subcomponents and components
  (our CAN framework includes more libraries common with our other projects,
   we need to separate some utility libraries etc.)
 - the rules in more spread Makefiles are way to the hell,
  (update for different kernel, RT-Linux etc would be nightmare in other case)
 - make system should allow to freely move with cross-dependant components
   without need to update users of moved component
  (I hate somethink like -I../../sched/rtlshwq/include in CAN makefiles
   for example. Component could be renamed to different name or version
   could be added to name and all Makefiles in CAN would require to
   be updated)
 - make system should be able to compile mutually cross-dependant libraries
   and should ensure, that change in one component sources or headers
   would result in relink or rebuild in components linked against that library
   or including modified header file
 - make system has to enable compilation out of OCERA full source tree
  (we would lost many users of particular components in other case)
 - compile should be able to do all above work without need to install
   any files before successful finish of build.
 - because we use some libraries for RT-Linux build and userspace
   build, we need to solve how to compile from same sources to both targets.
 - the build system should allow to call make for particular source
   subdirectory. Time of recursive make through all subdirectories is
   unacceptable.
 - make system should enable to build out of sources tree
  (else clean or working with CVS sandbox gets fussy and simultaneous
   multiple targets gets problematic)
 - it would be good, if there would be possibility to make from read-only
   media sources
 - make system should store results of build in some separate directory
   structure to simple install and testing
 - Makefiles in sources directories should be simple

There is probably only one alternative fully supporting above requirements
and it is GNU Autoheader...Automake...Autoconf... system.
But it is complicated and requires big amount of support files.
It would be acceptable if it could be easily used for OCERA framework.
But there are important show stopper for that system:
 - it would require deep revision of all OCERA CVS contents and agreement
   on this would be problematic
 - this system is not well prepared for dual compilation for Linux
   and RT-Linux sub-targets. It would mean many changes in default
   autoconf setup to support this. Probably simplest way would be
   to rebuild GCC tool chain for something like i586-elf-rtlinux.
   This would require even more space for OCERA development.

The problem calls for same solution, which would have minimal impact
on other components and would be elegant and would be maintainable
and small, because our main goal is components development and not
make systems development.

There is result of our trial. It is OMK make system.
The Makefile and Makefile.omk files should be in all source
directories. Common Makefile.rules file is required in the toplevel
sources directory. Alternatively this file could be moved
to link tree pointing into readonly media or can be anywhere
else if MAKERULES_DIR and SOURCES_DIR are specified.

Syntax of Makefile.omk files is for usual cases compatible
to Automake's Makefile.am descriptions. There are specific targets
for RT-Linux and Linux kernel related stuff

Makefile.omk user defined variables
# SUBDIRS          .. list of subdirectories intended for make from actual directory
# lib_LIBRARIES    .. list of the user-space libraries
# shared_LIBRARIES .. list of the user-space shared libraries
# kernel_LIBRARIES .. list of the kernel-space libraries
# rtlinux_LIBRARIES.. list of the RT-Linux kernel-space libraries
# include_HEADERS  .. list of the user-space header files
# nobase_include_HEADERS .. headers copied even with directory part
# kernel_HEADERS   .. list of the kernel-space  header files
# rtlinux_HEADERS  .. list of the RT-Linux kernel-space  header files
# bin_PROGRAMS     .. list of the require binary programs
# utils_PROGRAMS   .. list of the development utility programs
# kernel_MODULES   .. list of the kernel side modules/applications
# rtlinux_MODULES  .. list of RT-Linux the kernel side modules/applications
# xxx_SOURCES      .. list of specific target sources
# INCLUDES         .. additional include directories and defines for user-space
# kernel_INCLUDES  .. additional include directories and defines for kernel-space
# rtlinux_INCLUDES .. additional include directories and defines for RT-Linux
# default_CONFIG   .. list of default config assignments CONFIG_XXX=y/n ...

The Makefile is same for all sources directories and is only 14 lines long.
It is there only for convenience reasons to enable call "make" from
local directory. It contains code which locates Makefile.rules in actual
or any parent directory. With standard BASH environment it works such way,
that if you get into sources directory over symbolic links, it is able to
unwind yours steps back => you can make links to readonly media component
directories, copy Makefile.rules, Makefile and toplevel Makefile.omk,
adjust Makefile.omk to contain only required components and then call
make in top or even directories after crossing from your tree
to readonly media.

The system compiles all files out of source directories.
The actual version of system is adapted even for OCERA tree mode
if OCERA_DIR variable is defined in Makefile.rules

There are next predefined directory name components,
which can be adapted if required

BUILD_DIR_NAME = _build
	prefix of directory, where temporary build files are stored
COMPILED_DIR_NAME = _compiled
	prefix of directory, where final compilation results are stored
GROUP_DIR_NAME = yyy
	this is used for separation of build sub-trees in OCERA environment
	where more Makefile.rules is spread in the tree

Next directories are used:

KERN_BUILD_DIR   := $(MAKERULES_DIR)/$(BUILD_DIR_NAME)/kern
        directory to store intermediate files for kernel-space targets
USER_BUILD_DIR   := $(MAKERULES_DIR)/$(BUILD_DIR_NAME)/user
        directory to store intermediate files for user-space targets

USER_INCLUDE_DIR := $(MAKERULES_DIR)/$(COMPILED_DIR_NAME)/include
        directory to store exported include files which should be installed later
        on user-space include path
USER_LIB_DIR     := $(MAKERULES_DIR)/$(COMPILED_DIR_NAME)/lib
        same for user-pace libraries
USER_UTILS_DIR   := $(MAKERULES_DIR)/$(COMPILED_DIR_NAME)/bin-utils
        utilities for testing, which would not probably be installed
USER_BIN_DIR     := $(MAKERULES_DIR)/$(COMPILED_DIR_NAME)/bin
        binaries, which should go into directory on standard system PATH
        (/usr/local/bin, /usr/bin or $(prefix)/bin)

KERN_INCLUDE_DIR := $(MAKERULES_DIR)/$(COMPILED_DIR_NAME)/include-kern
        directory to store exported include files which should be installed later
        on kernel-space include path
KERN_LIB_DIR     := $(MAKERULES_DIR)/$(COMPILED_DIR_NAME)/lib-kern
        same for kernel-pace libraries
KERN_MODULES_DIR := $(MAKERULES_DIR)/$(COMPILED_DIR_NAME)/modules
        builded modules for Linux kernel or RT-Linux system

There is more recursive passes through directories to enable
mutual dependant libraries and binaries to compile.
Next passes are defined

default-config .. generates config.omk-default or xxx-default configuration file
check-dir      .. checks and creates required build directories
include-pass   .. copyes header files to USER_INCLUDE_DIR and KERN_INCLUDE_DIR
library-pass   .. builds objects in USER_BUILD_DIR/<relative path> and creates
                  libraries in USER_LIB_DIR
binary-pass and utils-pass .. links respective binaries
                in USER_{BIN,UTILS}_DIR directory. If some object file is missing
                it compiles it in  USER_BUILD_DIR/<relative path>
kernel-lib-pass .. builds libraries for kernel space targets
kernel-pass    .. builds kernel modules

The amount of passes is relatively high and consumes some time.
But only other way to support all required features is to assemble
one big toplevel Makefile, which would contain all components
and targets cross-dependencies.

Drawbacks of designed make system
 - the system is not as fast as we would like
 - it lacks Autoconf and configure extensive support for many systems
   from UNIX to DOS and WINDOWS
 - it does not contain support for checking existence of target libraries
   and functionalities as GNU Autoconf
 - it is heavily dependant on GNU MAKE program. But it would not be big
   problem, because even many commercial applications distribute GNU
   MAKE with them to be able to work in non-friendly systems
 - the key drawback is dependence on recent MAKE version 3.80 and better
   and even version 3.80 of MAKE has important bug, which has been
   corrected in newer sources

The last point is critical. I have not noticed it first, because
I use Slackware-9.2 and it contains latest released version 
of MAKE (version 3.80).
The problem appears when I have tried to build bigger libraries.
There is bug in version 3.80, which results in misleading
error "Virtual memory exhausted". It is known bug with ID 1517

    * long prerequisite inside eval(call()) => vm exhausted, Paul D. Smith

I have optimized some rules to not push memory to the edge,
but there could be still issues with 3.80 version.

I have downloaded latest MAKE CVS sources. The compilation required
separate lookup and download for .po files and full Autoheader... cycle.
I have put together package similar to release. Only ./configure --prefix=...
and make is required. CVS sources contains version 3.81beta1.
You can download prepared sources archive from

  http://cmp.felk.cvut.cz/~pisa/can/make-3.81beta1.tar.gz

The archive contains even "make" binary build by me, which should work
on other Linux distributions as well. 
Older version of MAKE (3.79.x released about year 2000) found
on Mandrake and RedHat are not sufficient and do not support eval feature.
I do not expect, that Debian would be more up-to-date or contain fixes
to MAKE vm exhausted bug.

The local CTU archive with our CAN components prepared for inclusion
into OCERA SF CVS could be found in my "can" directory

  http://cmp.felk.cvut.cz/~pisa/can/ocera-can-031212.tar.gz

The code should build for user-space with new make on most of Linux distros
when make is updated.

If you want to test compile for RT-Linux targets, line

#RTL_DIR := /home/cvs/ocera/ocera-build/kernel/rtlinux

in "Makefile.rules" has to be activated and updated
to point RT-Linux directory containing "rtl.mk".
There is only one library ("ulutrtl") and test utility compiled for RT-Linux
("can/utils/ulut/ul_rtlchk.c").

The next line ,if enabled, controls compilation in OCERA project tree

#OCERA_DIR := $(shell ( cd -L $(MAKERULES_DIR)/../../.. ; pwd -L ) )

The LinCAN driver has been updated to compile out of source directories.

Please, check, if you could compile CAN package and help us with integration
into OCERA SF CVS. Send your comments and objections. 

The OMK system has been adapted to support actual OCERA configuration process.
I am not happy with ocera.mk mix of defines and poor two or three rules,
but OMK is able to overcome that.

The OMK system has integrated rules (default-config) to build default configuration
file. The file is named "config.omk-default" for the stand-alone compilation.
The name corresponds to OCERA config + "-default" if OCERA_DIR is defined.
This file contains statements from all default_CONFIG lines in all Makefile.omk.
The file should be used for building of own "config.omk" file, or as list
for all options if Kconfig is used.