These are the installation instruction for the i2c package. There are three ways in which you can compile and install this package. Each has its own strong points. They are: 1. Complete separate from kernel compilation This will generate a set of modules which can be inserted and removed as needed; nothing will be written into the kernel tree; 2. Semi-integrated into the kernel This will add some files to your kernel tree, but has the advantage that module symbols are supported; the end result is functionally very like the previous way; 3. Patching of the kernel This will patch your kernel source tree. You must recompile your kernel to take advantage of this. But it makes it possible to compile drivers into the kernel itself, instead of having to add them as modules. Each of these ways will be described below in detail. We recommend using either method 1 or 3; method 2 is less well maintained. NOTE: OPTION 3 WILL CURRENTLY NOT WORK FOR 2.0 AND OLDER 2.1 KERNELS! Having a proper kernel tree (compilation options 1 and 2) ========================================================= Usually, if you compile a user-space application, you can get away with having a different version of the kernel running than the version of the kernel header files against which you compiled it. But a perfect match is needed for the first two compilation options above. Let's say you want to use the i2c modules with the kernel 2.1.12 you are running now. What you need, is the original tree in which you compiled that 2.1.12 kernel. A freshly unpacked 2.1.12 kernel will not cut it, because `make *config dep' creates some files that are needed. And even then, you will run into trouble, because you may not have selected the exact same configuration variables. Plain advise: if you do not have your original kernel tree anymore, recompile your kernel first. Note that there is no need for a perfect match at compilation time, just at run-time. This means you can cross-compile against a different kernel version, and the Makefile does not check for this. Usually problems if the match is imperfect, is that either this package won't compile at all (because it was a freshly unpacked tree without some files generated by `make *config dep'), or that you can't insert modules because of either a `kernel-module version mismatch' or because of `unresolved kernel symbols'. If you get either of these messages, check your kernel tree! Note that some distributions are notably bad at this. To offset this somewhat, not the files in /usr/include/{linux,asm} are used, but instead those in /usr/src/linux/include/{linux,asm}. It is also possible to tell the Makefile the kernel is somewhere else than at /usr/src/linux. Separate from kernel compilation (compilation option 1) ======================================================= This will compile and install the complete i2c package. Though nothing is written to your kernel tree, a proper tree is still needed for this. See earlier for what a proper kernel tree is. At the top of the Makefile are a couple of configuration variables that you may want to change. As far as possible, the Makefile tries to figure out by itself their settings, but it is possible to overrule them. A list is found below. Most important are the variables that determine where your kernel is located (LINUX=/usr/src/linux) and where you want to install your modules (MODDIR=/lib/modules/KERNELVERSION/extra/misc) and header files (LINUX_INCLUDE_DIR=/usr/local/include/linux). You can see that the installation locations are choosen in such a way that they are separate from the true kernel. Compilation is done by `make all'; `make install' installs the package. You will get a lot of warnings about files which are not found, all ending on `.d'. You can safely ignore this; they contain dependency information, which is regenerated on the spot. Please continue reading this file before you start compiling. Semi-integrated into the kernel compilation (compilation option 2) ================================================================== Please reconsider first whether you truly want to use this compilation option. Often, it is better to use the previous compilation technique. This will compile and install the complete i2c package, by using the kernel build system. Some file will be written to your kernel tree for this. At the top of the Makefile are a couple of configuration variables that you may want to change. Not all of those variables are used if you use this compilation option, though. A list of them is found below. Compilation is done by `make all'; `make install' installs the package. Please continue reading this file before you start compiling. Makefile configuration variables (compilation options 1 and 2) ============================================================== BUILD_SYSTEM (both) default: lm_sensors The build system which is used. lm_sensors corresponds with compilation option 1; i2c with compilatin option 2. SHELL (both) (default: /bin/sh) You may have to specify the full path to Bash here, if /bin/sh is some other shell. There have been conflicting reports on whether this is needed. LINUX (both) default: /usr/src/linux The location of your kernel tree. COMPILE_KERNEL (both) default: 1 Determine whether you want to consider the kernel modules for compilation at all. By default, compilation option 1 will only compile and install those modules which are not built into the kernel; compilation option 2 will compile and install all of them. If some modules are built into your kernel, and this package is much newer, you may find you can not insert the newly compiled modules. Sorry. You may want to set this to 0 if you have just patched and compiled your kernel using the same version of this package, and just want to compile the user-space tools. SMP (compilation option 1 only) This must be set to 1 for a SMP kernel. The magic invocation should determine this automatically, so you should not have to bother with this. MODVER (compilation option 1 only) This must be set to 1 if CONFIG_MODVERSIONS is defined. The magic invocation should determine this automatically, so you should not have to bother with this. MODDIR (both) default: /lib/modules/KERNELVERSION/extra/misc) The location where the kernel modules will be installed. LINUX_INCLUDE_DIR (compilation option 1 only) default: /usr/local/include/linux The location where the i2c header files will be installed WARN (compilation option 1 only) default: 0 Generate additional compilation warnings; mainly interesting for developers. Handling the modules (compilation option 2) =========================================== Once you have installed the kernel modules, you will have to make sure they are found. First, check whether your modutils will look in the right directory at all. If you used build system 1, you will probably have to add lines to /etc/conf.modules or /etc/modules.conf (use the one that exists, or take your pick): (modules-2.0.0): path[misc]=/lib/modules/current/extra/misc (modutils-2.1.x): path=/lib/modules/current/extra This assumes /lib/modules/current will always be linked to the correct modules tree. If not, you will have to change it as appropriate for your system. Next, you will have to run `depmod -a' to have them recognised. Most distributions run this command when you boot, so if you were cross- compiling, you can skip this step. Patching the kernel (compilation option 3) ========================================== There is a special script which should be able to generate diffs against any 2.0, 2.1, 2.2 and 2.3 kernel. Please report any problems to our mailinglist. Note that it may fail, and probably silently, if you have applied other patches to your kernel tree, or for very new kernels. It *is* safe to run it if your kernel already has the i2c drivers, or if it was patched with the lm_sensors drivers. The kernel diffs are generated by the program `mkpatch.pl' in the mkpatch subdirectory. It needs two arguments: the first one is the root of the i2c package, the second one is the root of the kernel tree against which the diffs will be generated. For example: cd /tmp/i2c-2.0.3 mkpatch/mkpatch.pl . /usr/src/linux > /tmp/i2c-patch You can apply the diffs as usual: cd /usr/src/linux patch -p1 -E < /tmp/i2c-patch Genearation and application can easily be done in one step: mkpatch/mkpatch.pl . /usr/src/linux | patch -p1 -E -d /usr/src/linux The generated diffs are of course only valid for the kernel version against which mkpatch.pl was run. Once you have applied the patches, you can configure and compile your kernel as usual. You will see the I2C configuration screen under the `Character Devices' menu in menuconfig. Using the I2C package ===================== You can now load the modules by using `modprobe'. For example, `modprobe i2c-elv' will load the i2c-elv modules, and all i2c modules on which it depends. You can not use demand-loading; you will have to issue explicit modprobe instructions. The one exception is the `i2c-dev' module. You can automatically load it by adding the following line to etc/conf.modules or /etc/modules.conf (use the one that exists): alias char-major-89 i2c-dev Note that there are no client drivers in this package; you will have to get them from somewhere else (for example, download the lm_sensors package at http://www.lm-sensors.nu). Without additional drivers and programs, this package is of very limited use to you. Old and new I2C drivers ======================= In the current 2.2 and 2.3 kernels, there are already I2C drivers, but they are not the same ones as in this package. They are much older, and have a very limited functionality compared with the drivers included here. Fortunately, they can co-exist peacefully, so you should not worry about it. Except for one thing: `#include ' can cause the wrong header file to be included. If you patched the kernel (compilation option 3), you will have to use `#include ' to include the old ones; in all other cases, including the old ones will probably be impossible without copying them explicitly to some place that will be checked first.