6. Various Aspects of Daily Work

6.1. Using an External Kernel Source Tree

This application note describes how to use an external kernel source tree within a PTXdist project. In this case the external kernel source tree is managed by GIT.

Cloning the Linux Kernel Source Tree

In this example we are using the officially Linux kernel development tree.

jbe@octopus:~$ git clone git://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git
[...]
jbe@octopus:~$ ls -l
[...]
drwxr-xr-x 38 jbe  ptx 4096 2015-06-01 10:21 myprj
drwxr-xr-x 25 jbe  ptx 4096 2015-06-01 10:42 linux
[...]

Configuring the PTXdist Project

Note

assumption is here, the directory /myprj contains a valid PTXdist project.

To make PTXdist use of this kernel source tree, instead of an archive we can simply create a link now:

jbe@octopus:~$ cd myprj
jbe@octopus:~/myprj$ mkdir local_src
jbe@octopus:~/myprj$ ptxdist local-src kernel ~/linux
jbe@octopus:~/myprj$ ls -l local_src
lrwxrwxrwx  1 jbe ptx   36 Nov 14 16:14 kernel.<platformname> -> /home/jbe/linux

Note

The <platformname> in the example above will be replaced by the name of your own platform.

PTXdist will handle it in the same way as a kernel part of the project. Due to this, we must setup:

  • Some kind of kernel version
  • Kernel configuration
  • Image type used on our target architecture
  • If we want to build modules
  • Patches to be used (or not)

Lets setup these topics. We just add the kernel component to it.

jbe@octopus:~/myprj$ ptxdist platformconfig

We must enable the Linux kernel entry first, to enable kernel building as part of the project. After enabling this entry, we must enter it, and:

  • Setting up the kernel version
  • Setting up the MD5 sum of the corresponding archive
  • Selecting the correct image type in the entry Image Type.
  • Configuring the kernel within the menu entry patching & configuration.
    • If no patches should be used on top of the selected kernel source tree, we keep the patch series file entry empty. As GIT should help us to create these patches for deployment, it should be kept empty on default in this first step.
    • Select a name for the kernel configuration file and enter it into the kernel config file entry.

Important

Even if we do not intend to use a kernel archive, we must setup these entries with valid content, else PTXdist will fail. Also the archive must be present on the host, else PTXdist will start a download.

Now we can leave the menu and store the new setup. The only still missing component is a valid kernel config file now. We can use one of the default config files the Linux kernel supports as a starting point. To do so, we copy one to the location, where PTXdist expects it in the current project. In a multi platform project this location is the platform directory usally in configs/<platform-directory>. We must store the file with a name selected in the platform setup menu (kernel config file).

Work Flow

Now its up to ourself working on the GIT based kernel source tree and using PTXdist to include the kernel into the root filesystem.

To configure the kernel source tree, we simply run:

jbe@octopus:~/myprj$ ptxdist kernelconfig

To build the kernel:

jbe@octopus:~/myprj$ ptxdist targetinstall kernel

To rebuild the kernel:

jbe@octopus:~/myprj$ ptxdist drop kernel compile
jbe@octopus:~/myprj$ ptxdist targetinstall kernel

6.2. Discovering Runtime Dependencies

Often it happens that an application on the target fails to run, because one of its dependencies is not fulfilled. This section should give some hints on how to discover these dependencies.

Dependencies on Shared Libraries

Getting the missed shared library for example at run-time is something easily done: The dynamic linker prints the missing library to the console.

To check at build time if all other dependencies are present is easy, too. The architecture specific readelf tool can help us here. It comes with the OSELAS.Toolchain and is called via <target>-readelf.

To test the foo binary from our new package FOO, we simply run:

$ ./selected_toolchain/<target>-readelf -d platform-<platformname>/root/usr/bin/foo | grep NEEDED
 0x00000001 (NEEDED)                     Shared library: [libm.so.6]
 0x00000001 (NEEDED)                     Shared library: [libz.so.1]
 0x00000001 (NEEDED)                     Shared library: [libc.so.6]

We now can check if all of the listed libraries are present in the root filesystem. This works for shared libraries, too. It is also a way to check if various configurations of our package are working as expected (e.g. disabling a feature should also remove the required dependency of this feature).

Dependencies on other Resources

Sometimes a binary fails to run due to missing files, directories or device nodes. Often the error message (if any) which the binary creates in this case is ambiguous. Here the strace tool can help us, namely to observe the binary at run-time. strace shows all the system calls the binary or its shared libraries are performing.

strace is one of the target debugging tools which PTXdist provides in its Debug Tools menu.

After adding strace to the root filesystem, we can use it and observe our foo binary:

$ strace usr/bin/foo
execve("/usr/bin/foo", ["/usr/bin/foo"], [/* 41 vars */]) = 0
brk(0)                                  = 0x8e4b000
access("/etc/ld.so.preload", R_OK)      = -1 ENOENT (No such file or directory)
open("/etc/ld.so.cache", O_RDONLY)      = 3
fstat64(3, {st_mode=S_IFREG|0644, st_size=77488, ...}) = 0
mmap2(NULL, 77488, PROT_READ, MAP_PRIVATE, 3, 0) = 0xb7f87000
close(3)                                = 0
open("/lib//lib/libm-2.5.1.so", O_RDONLY) = 3
read(3, "\177ELF\1\1\1\0\0\0\0\0\0\0\0\0\3\0\3\0\1\0\0\0p%\0\000"..., 512) = 512
mmap2(NULL, 4096, PROT_READ|PROT_WRITE, MAP_PRIVATE|MAP_ANONYMOUS, -1, 0) = 0xb7f86000
fstat64(3, {st_mode=S_IFREG|0555, st_size=48272, ...}) = 0
mmap2(NULL, 124824, PROT_READ|PROT_EXEC, MAP_PRIVATE|MAP_DENYWRITE, 3, 0) = 0xb7f67000
mmap2(0xb7f72000, 4096, PROT_READ|PROT_WRITE, MAP_PRIVATE|MAP_FIXED|MAP_DENYWRITE, 3, 0xb) = 0xb7f72000
mmap2(0xb7f73000, 75672, PROT_READ|PROT_WRITE, MAP_PRIVATE|MAP_FIXED|MAP_ANONYMOUS, -1, 0) = 0xb7f73000
close(3)                                = 0
open("/lib/libc.so.6", O_RDONLY)        = 3
read(3, "\177ELF\1\1\1\0\0\0\0\0\0\0\0\0\3\0\3\0\1\0\0\0\332X\1"..., 512) = 512
fstat64(3, {st_mode=S_IFREG|0755, st_size=1405859, ...}) = 0
[...]

Occasionally the output of strace can be very long and the interesting parts are lost. So, if we assume the binary tries to open a nonexisting file, we can limit the output to all open system calls:

$ strace -e open usr/bin/foo
open("/etc/ld.so.cache", O_RDONLY)      = 3
open("/lib/libm-2.5.1.so", O_RDONLY) = 3
open("/lib/libz.so.1.2.3", O_RDONLY) = 3
open("/lib/libc.so.6", O_RDONLY)        = 3
[...]
open("/etc/foo.conf", O_RDONLY) = -1 ENOENT (No such file or directory)

The binary may fail due to a missing /etc/foo.conf. This could be a hint on what is going wrong (it might not be the final solution).

6.3. Debugging with CPU emulation

If we do not need some target related feature to run our application, we can also debug it through a simple CPU emulation. Thanks to QEMU we can run ELF binaries for other architectures than our build host is.

Running an Application made for a different Architecture

PTXdist creates a fully working root filesystem with all run-time components in root/. Lets assume we made a PTXdist based project for a CPU. Part of this project is our application myapp we are currently working on. PTXdist builds the root filesystem and also compiles our application. It also installs it to usr/bin/myapp in the root filesystem.

With this preparation we can run it on our build host:

$ cd platform-versatilepb/root
platform-versatilepb/root$ qemu-<architecture> -cpu <cpu-core> -L . usr/bin/myapp

This command will run the application usr/bin/myapp built for an <cpu-core> CPU on the build host and is using all library compontents from the current directory.

For the stdin and -out QEMU uses the regular mechanism of the build host’s operating system. Using QEMU in this way let us simply check our programs. There are also QEMU environments for other architectures available.

Debugging an Application made for a different Architecture

Debugging our application is also possible with QEMU. All we need are a root filesystem with debug symbols available, QEMU and an architecture aware debugger.

The root filesystem with debug symbols will be provided by PTXdist, the architecture aware debugger comes with the OSELAS.Toolchain. Two consoles are required for this debug session in this example. We start the QEMU in the first console as:

$ cd ptxdistPlatformDir/root
ptxdistPlatformDir/root$ qemu-<architecture> -g 1234 -cpu <cpu-core> -L . usr/bin/myapp

Note

PTXdist always builds a root filesystems root/. It contains all components without debug information (all binaries are in the same size as used later on on the real target). In addition, each directory that contains binaries also contains a .debug/ directory. It contains a file with only the debug symbols for each binary. These files are ignored while running applications but GDB knows about it and will automatically load the debug files.

The added -g 1234 parameter lets QEMU wait for a GDB connection to run the application.

In the second console we start GDB with the correct architecture support. This GDB comes with the same OSELAS.Toolchain that was also used to build the project:

$ ./selected_toolchain/<target>-gdbtui platform-<platformname>/root/usr/bin/myapp

This will run a curses based GDB. Not so easy to handle (we must enter all the commands and cannot click with a mouse!), but very fast to take a quick look at our application.

At first we tell GDB where to look for debug symbols. The correct directory here is root/.

(gdb) set solib-absolute-prefix platform-<platformname>/root

Next we connect this GDB to the waiting QEMU:

(gdb) target remote localhost:1234
Remote debugging using localhost:1234
[New Thread 1]
0x40096a7c in _start () from root/lib/ld.so.1

As our application is already started, we can’t use the GDB command start to run it until it reaches main(). We set a breakpoint instead at main() and continue the application:

(gdb) break main
Breakpoint 1 at 0x100024e8: file myapp.c, line 644.
(gdb) continue
Continuing.
Breakpoint 1, main (argc=1, argv=0x4007f03c) at myapp.c:644

The top part of the running gdbtui console will always show us the current source line. Due to the root/ directory usage all debug information for GDB is available.

Now we can step through our application by using the commands step, next, stepi, nexti, until and so on.

Note

It might be impossible for GDB to find debug symbols for components like the main C run-time library. In this case they where stripped while building the toolchain. There is a switch in the OSELAS.Toolchain menu to keep the debug symbols also for the C run-time library. But be warned: This will enlarge the OSELAS.Toolchain installation on your harddisk! When the toolchain was built with the debug symbols kept, it will be also possible for GDB to debug C library functions our application calls (so it might worth the disk space).

6.4. Migration between Releases

To migrate an existing project from within one minor release to the next one, we do the following step:

~/my_bsp# ptxdist migrate

PTXdist will ask us for every new configuration entry what to do. We must read and answer these questions carefully. At least we shouldn’t answer blindly with ’Y’ all the time because this could lead into a broken configuration. On the other hand, using ’N’ all to time is more safer. We can still enable interesting new features later on.

6.5. Increasing Build Speed

Modern host systems are providing more than one CPU core. To make use of this additionally computing power recent applications should do their work in parallel.

Using available CPU Cores

PTXdist uses all available CPU cores when building a project by default. But there are some exceptions:

  • the prepare stage of all autotools build system based packages can use only one CPU core. This is due to the fact, the running “configure” is a shell script.
  • some packages have a broken buildsystem regarding parallel build. These kind of packages build successfully only when building on one single CPU core.
  • creating the root filesystem images are also done on a single core only

Manually adjusting CPU Core usage

Manual adjustment of the parallel build behaviour is possible via command line parameters.

-ji<number>
this defines the number of CPU cores to build a package. The default is two times the available CPU cores.
-je<number>
this defines the number of packages to be build in parallel. The default is one package at a time.
-j<number>
this defines the number of CPU cores to be used at the same time. These cores will be used on a package base and file base.
-l<number>
limit the system load to the given value.

Important

using -ji and -je can overload the system immediatley. These settings are very hard.

A much softer setup is to just use the -j<number> parameter. This will run up to <number> tasks at the same time which will be spread over everything to do. This will create a system load which is much user friendly. Even the filesystem load is smoother with this parameter.

Building in Background

To build a project in background PTXdist can be ’niced’.

-n[<number>]
run PTXdist and all of its child processes with the given nicelevel <number>. Without a nicelevel the default is 10.

Building Platforms in Parallel

Due to the fact that more than one platform can exist in a PTXdist project, all these platforms can be built in parallel within the same project directory. As they store their results into different platform subdirectories, they will not conflict. Only PTXdist must be called differently, because each call must be parametrized individually.

The used Platform Configuration

$ ptxdist platform <some-platform-config>

This call will create the soft link selected_platformconfig to the <some-platform-config> in the project’s directory. After this call, PTXdist uses this soft link as the default platform to build for.

It can be overwritten temporarily by the command line parameter --platformconfig=<different-platform-config>.

The used Project Configuration

$ ptxdist select <some-project-config>

This call will create the soft link selected_ptxconfig to the <some-project-config> in the project’s directory. After this call, PTXdist uses this soft link as the default configuration to build the project.

It can be overwritten temporarily by the command line parameter --ptxconfig=<different-project-config>.

The used Toolchain to Build

$ ptxdist toolchain <some-toolchain-path>

This call will create the soft link selected_toolchain to the <some-toolchain-path> in the project’s directory. After this call, PTXdist uses this soft link as the default toolchain to build the project with.

It can be overwritten temporarily by the command line parameter --toolchain=<different-toolchain-path>.

By creating the soft links all further PTXdist commands will use these as the default settings.

By using the three --platformconfig, --ptxconfig and --toolchain parameters, we can switch (temporarily) to a completely different setting. This feature we can use to build everything in one project.

A few Examples

The project contains two individual platforms, sharing the same architecture and same project configuration.

$ ptxdist select <project-config>
$ ptxdist toolchain <architecture-toolchain-path>
$ ptxdist --platformconfig=<architecture-A> --quiet go &
$ ptxdist --platformconfig=<architecture-B> go

The project contains two individual platforms, sharing the same project configuration.

$ ptxdist select <project-config>
$ ptxdist --platformconfig=<architecture-A> --toolchain=<architecture-A-toolchain-path> --quiet go &
$ ptxdist --platformconfig=<architecture-B> --toolchain=<architecture-B-toolchain-path> go

The project contains two individual platforms, but they do not share anything else.

$ ptxdist --select=<project-A-config> --platformconfig=<architecture-A> --toolchain=<architecture-A-toolchain-path> --quiet go &
$ ptxdist --select=<project-B-config> --platformconfig=<architecture-B> --toolchain=<architecture-B-toolchain-path> go

Running one PTXdist in background and one in foreground would render the console output unreadable. That is why the background PTXdist uses the --quiet parameter in the examples above. Its output is still available in the logfile under the platform build directory tree.

By using more than one virtual console, both PTXdists can run with their full output on the console.

6.6. Using a Distributed Compiler

To increase the build speed of a PTXdist project can be done by doing more tasks in parallel. PTXdist itself uses all available CPU cores by default, but is is limited to the local host. For further speedup a distributed compilation can be used. This is the task of ICECC aka icecream. With this feature a PTXdist project can make use of all available hosts and their CPUs in a local network.

Setting-Up the Distributed Compiler

How to setup the distributed compiler can be found on the project’s homepage at GITHUB:

https://github.com/icecc/icecream.

Read their README.md for further details.

Important

as of July 2014 you need at least an ICECC in its version 1.x. Older revisions are known to not work.

Enabling PTXdist for the Distributed Compiler

Since the 2014.07 release, PTXdist supports the usage of ICECC by simply enabling a setup switch.

Run the PTXdist setup and navigate to the new ICECC menu entry:

$ ptxdist setup
   Developer Options   --->
      [*] use icecc
      (/usr/lib/icecc/icecc-create-env) icecc-create-env path

Maybe you must adapt the icecc-create-env path to the setting on your host. Most of the time the default path should work.

How to use the Distributed Compiler with PTXdist

PTXdist still uses two times the count of cores of the local CPU for parallel tasks. But if a faster CPU in the net exists, ICECC will now start to do all compile tasks on this/these faster CPU(s) instead of the local CPU.

To really boost the build speed you must increase the tasks to be done in parallel manually. Use the -ji<x> command line option to start more tasks at the same time. This command line option just effects one package to build at a time. To more increase the build speed use the -je<x> command line option as well. This will build also packages in parallel.

A complete command line could look like this:

$ ptxdist go -ji64 -je8

This command line will run up to 64 tasks in parallel and builds 8 packages at the same time. Never worry again about your local host and how slow it is. With the help of ICECC every host will be a high speed development machine.

6.7. Using Pre-Built Archives

PTXdist is a tool which creates all the required parts of a target’s filesystem to breathe life into it. And it creates these parts from any kind of source files. If a PTXdist project consists of many packages the build may take a huge amount of time.

For internal checks we have a so called “ALL-YES” PTXdist project. It has - like the name suggests - all packages enabled which PTXdist supports. To build this “ALL-YES” PTXdist project our build server needs about 6 hours.

Introduction

While developing a PTXdist project it is necessary to clean and re-build everything from time to time to get a re-synced project result which honors all changes made in the project. But since cleaning and re-building everything from time to time is a very good test case for if some adaptions are still missing or if everything is complete, it can be a real time sink to do so.

To not lose developer’s temper when doing such tests, PTXdist can keep archives from the last run which includes all the files the package’s build system has installed while the PTXdist’s install stage runs for it.

The next time PTXdist shall build a package it can use the results from the last run instead. This feature can drastically reduce the time to re-build the whole project. But also, this PTXdist feature must be handled with care and so it is not enabled and used as default.

This section describes how to make use of this PTXdist feature and what pitfalls exist when doing so.

Creating Pre-Built Archives

To make PTXdist create pre-built archives, enable this feature prior to a build in the menu:

$ ptxdist menuconfig

    Project Name & Version --->
        [*] create pre-built archives

Now run a regular build of the whole project:

$ ptxdist go

When the build is finished, the directory packages contains additional archive files with the name scheme *-dev.tar.gz. These files are the pre-built archives which PTXdist can use later on to re-build the project.

Using Pre-Built Archives

To make PTXdist use pre-built archives, enable this feature prior to a build in the menu:

$ ptxdist menuconfig

    Project Name & Version --->
        [*] use pre-built archives
        (</some/path/to/the/archives>)

During the next build (e.g. ptxdist go) PTXdist will look for a specific package if its corresponding pre-built archive exists. If it exists and the used hash value in the pre-built archive’s filename matches, PTXdist will skip all source archive handling (extract, patch, compile and install) and just extract and use the pre-built archive’s content.

Sufficient conditions for safe application of pre-built archives are:

  • using one pre-built archive pool for one specific PTXdist project.
  • using a constant PTXdist version all the time.
  • using a constant OSELAS.Toolchain() version all the time.
  • no package with a pre-built archive in the project is under development.

The hash as a part of the pre-built archive’s filename only reflects the package’s configuration made in the menu (ptxdist menuconfig). If this package specific configuration changes, a new hash value will be the result and PTXdist can select the matching pre-built archive.

This hash value change is an important fact, as many things outside and inside the package can have a big impact of the binary result but without a hash value change!

Please be careful when using the pre-built archives if you:

  • intend to switch to a different toolchain with the next build.
  • change the patch set applied to the corresponding package, e.g. the package is under development.
  • change the hard coded configure settings in the package’s rule file, e.g. the package is under development.
  • intend to use one pre-built archive pool from different PTXdist projects.
  • change a global PTXdist configuration parameter (e.g. PTXCONF_GLOBAL_IPV6).

To consider all these precautions the generated pre-built archives are not transferred automatically to where the next build expects them. This must be done manually by the user of the PTXdist project. Doing so, we can decide on a package by package basis if its pre-built archive should be used or not.

If you are unsure if your modifications rendered some or all of your pre-built archives invalid you can always delete and build them again to be on the safe side.

Packages without Pre-Built Archives Support

Neither host nor cross related packages support pre-built archives. These kind of packages are always (re-)built.

Only target related packages can be used based on their pre-built archives, but there are a few exceptions:

  • Linux kernel: it has an incomplete install stage, which results in an incomplete pre-built archive. Due to this, it cannot be used as a pre-built archive.
  • Barebox bootloader: it has an incomplete install stage, which results in an incomplete pre-built archive. Due to this, it cannot be used as a pre-built archive.
  • a few somehow broken packages that are all explicitely marked with a <packagename>_DEVPKG := NO in their corresponding rule file.

Workflow with Pre-Built Archives

We are starting with an empty PTXdist project and enabling the pre-built archive feature as mentioned in the previous section. After that a regular build of the project can be made.

When the build is finished it’s time to copy all the pre-built archives of interest to where the next build will expect them. The previous section mentions the step to enable their use. It also allows to define a directory. The default path of this directory is made from various other menu settings to ensure the pre-built archives of the current PTXdist project do not conflict with pre-built archives of different PTXdist projects. To get an idea of what the final path is, we can ask PTXdist.

$ ptxdist print PTXCONF_PROJECT_DEVPKGDIR
/home/jbe/OSELAS.BSP/Pengutronix/OSELAS.BSP-Pengutronix-Generic

If this directory does not exist, we can simply create it:

$ mkdir -p /home/jbe/OSELAS.BSP/Pengutronix/OSELAS.BSP-Pengutronix-Generic

Now it’s time to copy the pre-built archives to this new directory. We could simply copy all pre-built archives from the /packages directory. But we should keep in mind, if any of the related packages are under development, we must omit their corresponding pre-built archives in this step.

$ cp platform-<platformname>/packages/*-dev.tar.gz /home/jbe/OSELAS.BSP/Pengutronix/OSELAS.BSP-Pengutronix-Generic

Use Cases

Some major possible use cases are covered in this section:

  • speed up a re-build of one single project.
  • share pre-built archives between two platforms based on the same architecture.
  • increase reproducibility of binaries.

To simply speed up a re-build of the whole project (without development on any of the used packages) we just can copy all *-dev.tar.gz archives after the first build to the location where PTXdist expects them at the next build time.

If two platforms are sharing the same architecture it is possible to share pre-built archives as well. The best way it can work is, if both platforms are part of the same PTXdist project. They must also share the same toolchain settings, patch series and rule files. If these precautions are handled the whole project can be built for the first platform and these pre-built archives can be used to build the project for the second platform. This can reduce the required time to build the second platform from hours to minutes.

6.8. Downloading Packages from the Web

Sometimes it makes sense to get all required source archives at once. For example prior to a shipment we want to also include all source archives, to free the user from downloading it by him/herself.

PTXdist supports this requirement by the export_src parameter. It collects all required source archives into one given single directory. To do so, the current project must be set up correctly, e.g. the select and platform commands must be ran prior the export_src step.

If everything is set up correctly we can run the following commands to get the full list of required archives to build the project again without an internet connection.

$ mkdir my_archives
$ ptxdist export_src my_archives

PTXdist will now collect all source archives to the my_archives/ directory.

Note

If PTXdist is configured to share one source archive directory for all projects, this step will simply copy the source archives from the shared source archive directory. Otherwise PTXdist will start to download them from the world wide web.

6.9. Creating Autotools based Packages

Developing your own programs and libraries can be one of the required tasks to support an embedded system. PTXdist comes with three autotoolized templates to provide a comfortable buildsystem:

  • a library package template
  • an executable package template
  • a program combined with a library package template

Some template components are shared between all three packages types and described here, some other template componente are indvidual to each package type and described later on.

Shared components

Some files and their content are used in all three packages types. Most of them need your attention and some adaptions and thus listed here.

M4 macros

Autotool based buildsystems use M4 macros for their detection and configuring features. Some of these M4 macros are generic and come with the autotools itself, some other are project specific and must be shipped with your package. The PTXdist autotoolized templates come with a few M4 macro files listed below:

$ tree m4/
m4/
|-- ptx.m4
|-- attributes.m4
|-- ax_code_coverage.m4
|-- pkg.m4
|-- ax_armv4_detection.m4
|-- ax_armv5_detection.m4
|-- ax_armv6_detection.m4
|-- ax_armv7_detection.m4
`-- ax_floating_point.m4

Note: these files contains M4 macros used in configure.ac.

The ptx.m4 file contains a list of tests, handy for many projects. They end up into options of the final configure script. These options are mentioned in the INSTALL file (see below). This file is used like some kind of library to keep the configure.ac small. The configure.ac just call an M4 macro from the ptx.m4 file and all details are handled there.

The attributes.m4 file contains various tests for compiler and linker options and flags. They are used in the ptx.m4 file.

The ax_code_coverage.m4 file provides a comfortable way to add the coverage feature to the buildsystem. It handles all the details how to parametrize the compiler and linker correctly.

The pkg.m4 must be shipped with a package which uses pkg-config to detect the existance of external libraries and query details how to use them. If your package doesn’t use pkg-config, you can remove this file (and remove it from the EXTRA_DIST variable in Makefile.am).

The ax_armv*_detection.m4/ax_floating_point.m4 files provide architecture specific M4 macros. If your code doesn’t depend on the architecture, you can remove these files (don’t forget to remove them from the EXTRA_DIST variable in Makefile.am in this case).

Note: if you use more non-generic M4 macros in your configure.ac file, don’t forget to add their source files to the m4/ directory. This will enable any user of your package to re-generate the autotools based files without providing all dependencies by themself.

Hints for a User of your Package

INSTALL

Prepared with some information about the package you provide. Be kind to the users of your package and write some sentences about basic features and usage of your package, how to configure it and how to build it. It already lists build-time options provided by the ptx.m4 M4 macro file.

Creating a Library Template

This template creates a library only package and can be done by the PTXdist’s newpackage option:

$ ptxdist newpackage src-autoconf-lib

ptxdist: creating a new 'src-autoconf-lib' package:

ptxdist: enter package name...........: foo
ptxdist: enter version number.........: 1
ptxdist: enter package author.........: Juergen Borleis <jbe@pengutronix.de>
ptxdist: enter package section........: project_specific

generating rules/foo.make
generating rules/foo.in

local_src/foo does not exist, create? [Y/n] Y
./
./configure.ac
./Makefile.am
./COPYING
./lib@name@.pc.in
./wizard.sh
./lib@name@.h
./@name@.c
./autogen.sh
mkdir: created directory 'm4'
./
./ax_armv6_detection.m4
./ptx.m4
./internal.h
./pkg.m4
./ax_armv4_detection.m4
./ax_floating_point.m4
./INSTALL
./ax_armv5_detection.m4
./attributes.m4
./ax_armv7_detection.m4
./ax_code_coverage.m4

After this step the new directory local_src/foo exists and contains various template files. All of these files are dedicated to be modified by yourself.

The content of this directory is:

$ tree local_src/foo/
local_src/foo/
|-- COPYING
|-- INSTALL
|-- Makefile.am
|-- autogen.sh
|-- configure.ac
|-- foo.c
|-- internal.h
|-- libfoo.h
|-- libfoo.pc.in
`-- m4/
    |-- ptx.m4
    |-- attributes.m4
    |-- ax_code_coverage.m4
    |-- pkg.m4
    |-- ax_armv4_detection.m4
    |-- ax_armv5_detection.m4
    |-- ax_armv6_detection.m4
    |-- ax_armv7_detection.m4
    `-- ax_floating_point.m4

Most files and their content are already described above. Some files and their content are library specific:

Build system related files

configure.ac

The shared part is already described above. For a library there are some extensions:

LT_CURRENT / LT_REVISION / LT_AGE

define the binary compatibility of your library. The rules how these numbers are defined are:

  • library code was modified: LT_REVISION++
  • interfaces changed/added/removed: LT_CURRENT++ and LT_REVISION = 0
  • interfaces added: LT_AGE++
  • interfaces removed: LT_AGE = 0

You must manually change these numbers whenever you change the code in your library prior a release.

REQUIRES
to enrich the generated *.pc file for easier dependency handling you should also fill the REQUIRES variable. Here you can define from the package management point of view the dependencies of your library. For example if your library depends on the udev library and requires a specific version of it, just add the string udev >= 1.0.0 to the REQUIRES variable. Note: the listed packages must be space-separated.
CONFLICTS
if your library conflicts with a different library, add this different library to the CONFLICTS variable (from the package management point of view).

libfoo.pc.in

This file gets installed to support the pkg-config tool for package management. It contains some important information for users of your package how to use your library and also handles its dependencies. Some TODOs in this file need your attention:

Name
A human-readable name for the library.
Description
add a brief description of your library here
Version
the main revision of the library. Will automatically replaced from your settings in configure.ac.
URL
where to find your library. Will automatically replaced from your settings in configure.ac.
Requires
space-separated list of modules your library itself depends on and managed by pkg-config. The listed modules gets honored for the static linking case and should not be given again in the Libs.private line. This line will be filled by the REQUIRES variable from the configure.ac.
Requires.private
space-separated list of modules your library itself depends on and managed by pkg-config. The listed modules gets honored for the static linking case and should not be given again in the Libs.private line. This line will be filled by the REQUIRES variable from the configure.ac.
Conflicts
list of packages your library conflicts with. Will automatically replaced from your CONFLICTS variable settings in configure.ac.
Libs
defines the linker command line content to use your library and link it against other applications or libraries
Libs.private
defines the linker command line content to use your library and link it against other application or libraries statically. List only libraries here which are not managed by pkg-config (e.g. do not conflict with modules given in the Requires). This line will be filled by the LIBS variable from the configure.ac.
Cflags
required compile flags to make use of your library. Unfortunately you must mix CPPFLAGS and CFLAGS here which is a really bad idea.

It is not easy to fully automate the adaption of the pc file. At least the lines Requires, Requires.private and Libs.private are hardly to fill for packages which are highly configureable.

I nice and helpful description about this kind of configuration file can be found here:

Creating an Executable Template

Creating an executable template works nearly the same like the example above in Creating a Library Template. It just skips the library related stuff.

The command:

$ ptxdist newpackage src-autoconf-prog

Results into the following generated files:

$ tree local_src/foo
|-- COPYING
|-- INSTALL
|-- Makefile.am
|-- autogen.sh
|-- configure.ac
|-- foo.c
|-- internal.h
`-- m4/
    |-- ptx.m4
    |-- attributes.m4
    |-- ax_code_coverage.m4
    |-- pkg.m4
    |-- ax_armv4_detection.m4
    |-- ax_armv5_detection.m4
    |-- ax_armv6_detection.m4
    |-- ax_armv7_detection.m4
    `-- ax_floating_point.m4

Creating an Executable with a Library Template

Creating a library and an executable which makes use of this library is a combination of Creating a Library Template and Creating an Executable Template.

The command:

$ ptxdist newpackage src-autoconf-proglib

Results into the following generated files:

$ tree local_src/foo
|-- COPYING
|-- INSTALL
|-- Makefile.am
|-- autogen.sh
|-- configure.ac
|-- internal.h
|-- libfoo.c
|-- libfoo.h
|-- libfoo.pc.in
|-- foo.c
`-- m4/
    |-- ptx.m4
    |-- attributes.m4
    |-- ax_code_coverage.m4
    |-- pkg.m4
    |-- ax_armv4_detection.m4
    |-- ax_armv5_detection.m4
    |-- ax_armv6_detection.m4
    |-- ax_armv7_detection.m4
    `-- ax_floating_point.m4

The intended purpose of this template is a new tool, which has all its features implemented in the library. And the executable is a shell command frontend to provide the library’s features to an interactive user.

The advantage of this approach is, the library’s features can also be used by a non-interactive user, e.g. a different application.

Note

If you intend to use the GPL license, think about using the LGPL license variant for the library part of your project.

Important

If you want to be able to move code from the executable (and GPL licensed) part into the library (and LGPL licensed) part later on, you should use the LGPL license for both parts from the beginning. Else you may cannot move source code in such a way, because it would require a license change for this specific piece of source code (to be pedantic!).

6.10. Using a userland NFS Server for the Target

To improve the development of software for a target system, it is very exhausting changing files or settings at the target itself.

Or trying the application under development on the target again and again to see if a feature works or a GUI looks nicer now or is more handy to control on a small touchscreen display.

Using the Network File System (NFS) can improve the development speed by grades in this case. Everything filesystem related is still happening on the development host and each modification can be used at the target immediately.

Using PTXdist’s built-in NFS Userland Server

PTXdist can export the BSP’s root filesystem by itself. Since a userspace tool running as a regular user cannot open network ports below 1024, it uses a different network port. The default is port 2049. To make use of this PTXdist feature, run inside the BSP at your development host:

$ ptxdist nfsroot
[...]
Mount rootfs with nfsroot=/root,v3,tcp,port=2049,mountport=2049

At the target side a slighly different configuration must be used to work with the userspace NFS server PTXdist provides instead of a regular kernel space NFS server the Linux kernel provides. When starting PTXdist’s nfsroot feature it outputs the special command line we need to instruct the Linux kernel to use this userland NFS server for its root filesystem to boot its userland from.

What is still to be considered here is the network confiuration. Refer the kernel documentation about the capabilities of the ip= kernel command line option and check, if we need to setup a special IP address at the target side to reach the host running PTXdist and its nfsroot feature.

If we need a special IP address to setup, the kernel command line parameter to use PTXdist’s nfsroot feature, the parameter looks like this:

nfsroot=<host-ip>:/root,v3,tcp,port=2049,mountport=2049

In the case we must replace the <host-ip> part of the line above with the IP address of our host running PTXdist’s nfsroot feature.

If we run a recent Barebox bootloader with bootspec support, booting a target via network only is very easy. In the Barebox prompt just enter:

barebox@target:/ boot nfs://<host-ip>:2049//root

In this case Barebox will mount the defined root filesysem via NFS, loads the included bootspec file, read its information and continues to load the matching kernel and maybe a matching device tree.

6.11. Working with GIT sources

TBD

6.12. The PTXdist User Manual

The HTML based PTXdist user manual can be found in web at

http://www.ptxdist.org/

Requirements to build the Documentation

PTXdist can build its own user manual and supports HTML or PDF as the output formats. PTXdist uses the Sphinx documentaion maker to build both output formats. The host system itself must provide some tools and data:

Fonts:
  • Liberation Sans/Liberation Sans Bold or DejaVu Sans/DejaVu Sans Bold (for the “Portable Document Format”, e.g. PDF)
  • Inconsolata, DejaVu Sans Mono or Liberation Sans Mono (for the “Portable Document Format”, e.g. PDF)
Tools:
  • Sphinx version 1.3.4, better 1.4.2…1.4.9 or >= 1.6.5 (for all kind of document formats)
  • Sphinx theme from https://readthedocs.org/
  • TeX Live 2016 (for the “Portable Document Format”, e.g. PDF)

Using a Python virtual environment

Sphinx is Python based and thus can be installed via a virtual environment when not globally present in the host system.

$ pip3 install --upgrade --user pip virtualenv
$ source env/bin/activate
$ pip3 install sphinx
$ pip3 install sphinx_rtd_theme

Note

Whenever you want to create the PTXdist user manual, you must first source the env/bin/activate file if not already done or do each PTXdist call with the –virtualenv=<dir> parameter.

Building the Documentation

PTXdist comes with support to generate HTML or Portable Document Format based documentation from the sources.

The command:

$ ptxdist docs-html

will build the HTML based documentation into Documentation/html and the entry file for this kind of documentation is Documentation/html/index.html.

The command:

$ ptxdist docs-latex

will build the Latex based documentation which results into the final Portable Document Format document. This result can be found in Documentation/latex/OSELAS.BSP-Pengutronix-Example-Quickstart.pdf.

Both commands can be executed in the BSP or the toplevel PTXdist directory to create the BSP specific or generic documentation respectively.

6.13. Integrate project specific Documentation into the Manual

PTXdist supports the ability to integrate project specific documentation into the final PTXdist manual. To do so, PTXdist handles file replacements and additions, while generating the documentation.

File replacement is working in the same manner like for all other files in a PTXdist based project: a local file with the same name superseds a global file from PTXdist.

With this mechanism we can replace existing PTXdist documentation or add new one.

If we want to add a new global section to the manual we can copy the global PTXdist doc/index.rst file into our local doc/ directory and adapt it accordingly.

To change or add things less intrusive we can do it on the various *.inc files in the PTXdist’s doc/ directory which define the content of the sections.

For example to change the image createn section’s content, we can copy the global PTXdist doc/user_images.inc into our local doc/ directory and adapt it to the behaviour of our project.

In the generic documentation source many text uses variables instead of fixed content. These variables are filled with values extracted from the current PTXdist project prior building the final documentation. Since PTXdist projects are bound to a defined PTXdist version and toolchain version, this kind of information is extracted from the current settings and substituted in the documentation. This behaviour ensures the documentaiton includes the project’s exact definition to external dependencies.

Refer the PTXdist file doc/conf.py for more information on variable substitution. This PTXdist global file can be superseded by a local copy as well.