1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
93
94
95
96
97
98
99
100
101
102
103
|
<!DOCTYPE HTML PUBLIC "-//W3C//DTD HTML 4.0 Transitional//EN"><html><head><meta http-equiv="Content-Type" content="text/html; charset=ISO-8859-1"><title>Qt Toolkit - Adding an accelerated graphics driver to Qt/Embedded</title><style type="text/css"><!--
h3.fn,span.fn { margin-left: 1cm; text-indent: -1cm; }
a:link { color: #004faf; text-decoration: none }
a:visited { color: #672967; text-decoration: none }body { background: white; color: black; }
--></style></head><body bgcolor="#ffffff">
<p>
<table width="100%">
<tr><td><a href="index.html">
<img width="100" height="100" src="qtlogo.png"
alt="Home" border="0"><img width="100"
height="100" src="face.png" alt="Home" border="0">
</a><td valign=top><div align=right><img src="dochead.png" width="472" height="27"><br>
<a href="classes.html"><b>Classes</b></a>
-<a href="annotated.html">Annotated</a>
- <a href="hierarchy.html">Tree</a>
-<a href="functions.html">Functions</a>
-<a href="index.html">Home</a>
-<a href="topicals.html"><b>Structure</b></a>
</div>
</table>
<h1 align=center> Adding an accelerated graphics driver to Qt/Embedded</h1><br clear="all">
<p>
Qt/Embedded has the capacity to make use of hardware accelerators.
To do so for a PCI or AGP driver, you need to perform the following steps:
<p>
1) Define an accelerated descendant of QLinuxFbScreen. This
should implement QVoodooScreen::connect to map its registers.
Use qt_probe_bus to get a pointer to PCI config space. This is where
you should check that you're being pointed at the right device
(using PCI device/manufacturer ID information). Then use PCI config
space to locate your device's accelerator registers in physical memory
and mmap the appropriate region in from /dev/mem. There is no need to
map the framebuffer, QLinuxFbScreen will do this for you. Return FALSE
if a problem occurs at any point.
QVoodooScreen::initDevice will be called only by the QWS server and
is guaranteed to be called before any drawing is done (and so is a good place
to set registers to known states). connect will be called by every connecting
client.
<p>
2) Define an accelerated descendant of QGfxRaster. This is where the actual
drawing code goes. Anything not implemented by hardware can be passed
back to QGfxRaster to do in software. Use the optype variable to make
sure that accelerated and unaccelerated operations are synchronised
(if you start drawing via software into an area where the hardware accelerator
is still drawing then your drawing operations will appear to be in the
wrong order). optype is stored in shared memory and is set to 0 by
unaccelerated operations; accelerated operations should set it to 1.
When a software graphics operation is requested and optype is 1,
QGfxRaster::sync() is called; you should provide your own implementation
of this which waits for the graphics engine to go idle. lastop is also
available for optimisation and is stored in the shared space
- this will not be set by the software-only QGfx and can be used to store
the type of your last operation (e.g. drawing a rectangle) so that part
of the setup for the next operation can be avoided when a lot of the same
operations are performed in sequence.
All drawing operations should be protected via a QWSDisplay::grab()
before any registers, lastop or optype are accessed, and ungrabbed() at the
end. This prevents two applications trying to access the accelerator at once
and possibly locking up the machine. It's possible that your source
data is not on the graphics card so you should check in such cases and
fall back to software if necessary. Note that QGfxRaster supports some
features not directly supported by QPainter (for instance, alpha channels
in 32-bit data and stretchBlt's). These features are used by Qt;
stretchBlt speeds up QPixmap::xForm and drawPixmap into a transformed
QPainter, alpha channel acceleration is supported for 32-bit pixmaps.
<p>
3) If you wish, define an accelerated descendant of QScreenCursor.
restoreUnder,saveUnder,drawCursor and draw should be defined as
null operations. Implement set, move, show and hide. 4k is left for your
cursor at the end of the visible part of the framebuffer
(i.e. at (width*height*depth)/8 )
<p>
4) Implement initCursor and createGfx in your QScreen descendant.
Implement useOffscreen and return true if you can make use of offscreen
graphics memory.
<p>
5) Implement a small function qt_get_screen_mychip, which simply
returns a new QMychipScreen
<p>
6) Add your driver to the DriverTable table in qgfxraster_qws.cpp
- e.g.
<p>
{ "MyChip", qt_get_screen_mychip,1 },
<p>
The first parameter is the name used with QWS_DISPLAY to request your
accelerated driver.
<p>
7) To run with your new driver,
export QWS_DISPLAY=MyChip (optionally MyChip:/dev/fb<n> to request a
different Linux framebuffer than /dev/fb0)
run the program
<p>
If your driver is not PCI or AGP you'll need to inherit QScreen instead
of QLinuxFbScreen and implement similar functionality to QLinuxFbScreen,
but otherwise the process should be similar. The most complete example
driver is qgfxmach64_qws.cpp; qgfxvoodoo_qws.cpp may provide a smaller
and more easy to understand driver.
<p><address><hr><div align="center">
<table width="100%" cellspacing="0" border="0"><tr>
<td>Copyright 2000 Trolltech<td><a href="http://www.trolltech.com/trademarks.html">Trademarks</a>
<td align="right"><div align="right">Qt version 2.3.1</div>
</table></div></address></body></html>
|
