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/****************************************************************************
**
** Copyright (C) 2011 Nokia Corporation and/or its subsidiary(-ies).
** All rights reserved.
** Contact: Nokia Corporation (qt-info@nokia.com)
**
** This file is part of the documentation of the Qt Toolkit.
**
** $QT_BEGIN_LICENSE:FDL$
** No Commercial Usage
** This file contains pre-release code and may not be distributed.
** You may use this file in accordance with the terms and conditions
** contained in the Technology Preview License Agreement accompanying
** this package.
**
** GNU Free Documentation License
** Alternatively, this file may be used under the terms of the GNU Free
** Documentation License version 1.3 as published by the Free Software
** Foundation and appearing in the file included in the packaging of this
** file.
**
** If you have questions regarding the use of this file, please contact
** Nokia at qt-info@nokia.com.
** $QT_END_LICENSE$
**
****************************************************************************/
/*!
\page qt-embedded-crosscompiling.html
\title Cross-Compiling Qt for Embedded Linux Applications
\ingroup qt-embedded-linux
Cross-compiling is the process of compiling an application on one
machine, producing executable code for a different machine or
device. To cross-compile a \l{Qt for Embedded Linux} application,
use the following approach:
\tableofcontents
\note The cross-compiling procedure has the configuration
process in common with the installation procedure; i.e., you might
not necessarily have to perform all the mentioned actions
depending on your current configuration.
\section1 Step 1: Set the Cross-Compiler's Path
Specify which cross-compiler to use by setting the \c PATH
environment variable. For example, if the current shell is bash,
ksh, zsh or sh:
\snippet doc/src/snippets/code/doc_src_emb-crosscompiling.qdoc 0
\section1 Step 2: Create a Target Specific qmake Specification
The qmake tool requires a platform and compiler specific \c
qmake.conf file describing the various default values, to generate
the appropriate Makefiles. The standard \l{Qt for Embedded Linux}
distribution provides such files for several combinations of
platforms and compilers. These files are located in the
distribution's \c mkspecs/qws subdirectory.
Each platform has a default specification. \l{Qt for Embedded Linux} will
use the default specification for the current platform unless told
otherwise. To override this behavior, you can use the \c configure
script's \c -platform option to change the specification for the host
platform (where compilation will take place).
The \c configure script's \c -xplatform option is used to provide a
specification for the target architecture (where the library will be
deployed).
For example, to cross-compile an application to run on a device with
an ARM architecture, using the GCC toolchain, run the configure
script at the command line in the following way:
\snippet doc/src/snippets/code/doc_src_emb-crosscompiling.qdoc 1
If neither of the provided specifications fits your target device,
you can create your own. To create a custom \c qmake.conf file,
just copy and customize an already existing file. For example:
\snippet doc/src/snippets/code/doc_src_emb-crosscompiling.qdoc 2
\note When defining a mkspec for a Linux target, the directory must
be prefixed with "linux-". We recommend that you copy the entire
directory.
Note also that when providing you own qmake specifcation, you must
use the \c configure script's \c -xplatform option to make
\l{Qt for Embedded Linux} aware of the custom \c qmake.conf file.
\section1 Step 3: Provide Architecture Specific Files
Starting with Qt 4, all of Qt's implicitly shared classes can
safely be copied across threads like any other value classes,
i.e., they are fully reentrant. This is accomplished by
implementing reference counting operations using atomic hardware
instructions on all the different platforms supported by Qt.
To support a new architecture, it is important to ensure that
these platform-specific atomic operations are implemented in a
corresponding header file (\c qatomic_ARCH.h), and that this file
is located in Qt's \c src/corelib/arch directory. For example, the
Intel 80386 implementation is located in \c
src/corelib/arch/qatomic_i386.h.
See the \l {Implementing Atomic Operations} documentation for
details.
\section1 Step 4: Provide Hardware Drivers
Without the proper mouse and keyboard drivers, you will not be
able to give any input to your application when it is installed on
the target device. You must also ensure that the appropriate
screen driver is present to make the server process able to put
the application's widgets on screen.
\l{Qt for Embedded Linux} provides several ready-made mouse, keyboard and
screen drivers, see the \l{Qt for Embedded Linux Pointer Handling}{pointer
handling}, \l{Qt for Embedded Linux Character Input}{character input} and
\l{Qt for Embedded Linux Display Management}{display management}
documentation for details.
In addition, custom drivers can be added by deriving from the
QWSMouseHandler, QWSKeyboardHandler and QScreen classes
respectively, and by creating corresponding plugins to make use of
Qt's plugin mechanism (dynamically loading the drivers into the
server application at runtime). Note that the plugins must be
located in a location where Qt will look for plugins, e.g., the
standard \c plugin directory.
See the \l {How to Create Qt Plugins} documentation and the \l
{tools/plugandpaint}{Plug & Paint} example for details.
\section1 Step 5: Build the Target Specific Executable
Before building the executable, you must specify the target
architecture as well as the target specific hardware drivers by
running the \c configure script:
\snippet doc/src/snippets/code/doc_src_emb-crosscompiling.qdoc 3
It is also important to make sure that all the third party
libraries that the application and the Qt libraries require, are
present in the tool chain. In particular, if the zlib and jpeg
libraries are not available, they must be included by running the
\c configure script with the \c -L and \c -I options. For example:
\snippet doc/src/snippets/code/doc_src_emb-crosscompiling.qdoc 4
The JPEG source can be downloaded from \l http://www.ijg.org/. The
\l{Qt for Embedded Linux} distribution includes a version of the zlib source
that can be compiled into the Qt for Embedded Linux library. If integrators
wish to use a later version of the zlib library, it can be
downloaded from the \l http://www.gzip.org/zlib/ website.
Then build the executable:
\snippet doc/src/snippets/code/doc_src_emb-crosscompiling.qdoc 5
That's all. Your target specific executable is ready for deployment.
\table 100%
\row
\o \bold {See also:}
\l{Qt for Embedded Linux Architecture} and \l{Deploying Qt for Embedded Linux
Applications}.
\endtable
*/
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