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141 lines
5.9 KiB
141 lines
5.9 KiB
/****************************************************************************
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**
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** Help with writing Qt/Embedded accelerated drivers
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**
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** Copyright (C) 1992-2008 Trolltech ASA. All rights reserved.
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**
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** This file is part of the Qt GUI Toolkit.
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**
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** This file may be used under the terms of the GNU General
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** Public License versions 2.0 or 3.0 as published by the Free
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** Software Foundation and appearing in the files LICENSE.GPL2
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** and LICENSE.GPL3 included in the packaging of this file.
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** Alternatively you may (at your option) use any later version
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** of the GNU General Public License if such license has been
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** publicly approved by Trolltech ASA (or its successors, if any)
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** and the KDE Free Qt Foundation.
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**
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** Please review the following information to ensure GNU General
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** Public Licensing requirements will be met:
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** http://trolltech.com/products/qt/licenses/licensing/opensource/.
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** If you are unsure which license is appropriate for your use, please
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** review the following information:
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** http://trolltech.com/products/qt/licenses/licensing/licensingoverview
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** or contact the sales department at sales@trolltech.com.
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**
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** This file may be used under the terms of the Q Public License as
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** defined by Trolltech ASA and appearing in the file LICENSE.QPL
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** included in the packaging of this file. Licensees holding valid Qt
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** Commercial licenses may use this file in accordance with the Qt
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** Commercial License Agreement provided with the Software.
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**
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** This file is provided "AS IS" with NO WARRANTY OF ANY KIND,
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** INCLUDING THE WARRANTIES OF DESIGN, MERCHANTABILITY AND FITNESS FOR
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** A PARTICULAR PURPOSE. Trolltech reserves all rights not granted
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** herein.
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**
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**********************************************************************/
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/*!
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\page emb-accel.html
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\title Adding an accelerated graphics driver to Qt/Embedded
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Qt/Embedded has the capacity to make use of hardware accelerators.
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To use a hardware accelerator for a PCI or AGP driver, you must
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perform the following steps:
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\list 1
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\i
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Define an accelerated descendant of QLinuxFbScreen.
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This should implement \c QVoodooScreen::connect() to map its
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registers. Use \c qt_probe_bus to get a pointer to the PCI config
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space. This is where you should check that you're being pointed to the
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right device (using the PCI device/manufacturer ID information). Then
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use PCI config space to locate your device's accelerator registers in
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physical memory and mmap the appropriate region from \c /dev/mem.
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There is no need to map the framebuffer, \c QLinuxFbScreen will do
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this for you. Return \c FALSE if a problem occurs at any point. \c
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QVoodooScreen::initDevice() will be called only by the QWS server and
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is guaranteed to be called before any drawing is done (and so is a
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good place to set registers to known states). \c connect() will be called
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by every connecting client.
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\i
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Define an accelerated descendant of QGfxRaster.
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This is where the actual drawing code goes. Anything not implemented
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in hardware can be passed back to \c QGfxRaster to do in software. Use
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the optype variable to make sure that accelerated and unaccelerated
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operations are synchronised (if you start drawing via software into an
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area where the hardware accelerator is still drawing then your drawing
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operations will appear to be in the wrong order). optype is stored in
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shared memory and is set to 0 by unaccelerated operations; accelerated
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operations should set it to 1. When a software graphics operation is
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requested and optype is 1, \c QGfxRaster::sync() is called; you should
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provide your own implementation of this that waits for the graphics
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engine to go idle. lastop is also available for optimisation and is
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stored in the shared space: this will not be set by the software-only
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\c QGfx and can be used to store the type of your last operation (e.g.
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drawing a rectangle) so that part of the setup for the next operation
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can be avoided when many of the same operations are performed in
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sequence.
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All drawing operations should be protected via a \c QWSDisplay::grab()
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before any registers, lastop or optype are accessed, and \c
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ungrabbed() at the end. This prevents two applications trying to
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access the accelerator at once and possibly locking up the machine.
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It's possible that your source data is not on the graphics card so you
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should check in such cases and fall back to software if necessary.
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Note that \c QGfxRaster supports some features not directly supported
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by QPainter (for instance, alpha channels in 32-bit data and
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stretchBlt's). These features are used by Qt; stretchBlt speeds up \c
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QPixmap::xForm() and \c drawPixmap() into a transformed \c QPainter,
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alpha channel acceleration is supported for 32-bit pixmaps.
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\i
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If you wish, define an accelerated descendant of \c QScreenCursor. \c
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restoreUnder(), \c saveUnder(), \c drawCursor() and \c draw() should
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be defined as null operations. Implement \c set(), \c move(), \c
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show() and \c hide(). 4KB is left for your cursor at the end of the
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visible part of the framebuffer (i.e. at (width*height*depth)/8 )
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\i
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Implement \c initCursor() and \c createGfx() in your \c QScreen
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descendant. Implement \c useOffscreen() and return \c TRUE if you can
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make use of offscreen graphics memory.
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\i
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Implement a small function \c qt_get_screen_mychip(), which simply
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returns a new \c QMychipScreen
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\i
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Add your driver to the DriverTable table in \c qgfxraster_qws.cpp,
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e.g.
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\code
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{ "MyChip", qt_get_screen_mychip,1 },
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\endcode
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The first parameter is the name used with QWS_DISPLAY to request your
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accelerated driver.
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\i
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To run with your new driver,
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\code
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export QWS_DISPLAY=MyChip
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\endcode
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(optionally MyChip:/dev/fb\<n\> to request a different Linux
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framebuffer than \c /dev/fb0), then run the program
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\endlist
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If your driver is not PCI or AGP you'll need to inherit \c QScreen
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instead of \c QLinuxFbScreen and implement similar functionality to \c
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QLinuxFbScreen, but otherwise the process should be similar. The most
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complete example driver is \c qgfxmach64_qws.cpp; \c
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qgfxvoodoo_qws.cpp may provide a smaller and easier-to-understand
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driver.
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*/
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