| 1 |
3 |
xianfeng |
|
| 2 |
|
|
This is a first start for some documentation about frame buffer device
|
| 3 |
|
|
internals.
|
| 4 |
|
|
|
| 5 |
|
|
Geert Uytterhoeven , 21 July 1998
|
| 6 |
|
|
James Simmons , Nov 26 2002
|
| 7 |
|
|
|
| 8 |
|
|
--------------------------------------------------------------------------------
|
| 9 |
|
|
|
| 10 |
|
|
*** STRUCTURES USED BY THE FRAME BUFFER DEVICE API ***
|
| 11 |
|
|
|
| 12 |
|
|
The following structures play a role in the game of frame buffer devices. They
|
| 13 |
|
|
are defined in .
|
| 14 |
|
|
|
| 15 |
|
|
1. Outside the kernel (user space)
|
| 16 |
|
|
|
| 17 |
|
|
- struct fb_fix_screeninfo
|
| 18 |
|
|
|
| 19 |
|
|
Device independent unchangeable information about a frame buffer device and
|
| 20 |
|
|
a specific video mode. This can be obtained using the FBIOGET_FSCREENINFO
|
| 21 |
|
|
ioctl.
|
| 22 |
|
|
|
| 23 |
|
|
- struct fb_var_screeninfo
|
| 24 |
|
|
|
| 25 |
|
|
Device independent changeable information about a frame buffer device and a
|
| 26 |
|
|
specific video mode. This can be obtained using the FBIOGET_VSCREENINFO
|
| 27 |
|
|
ioctl, and updated with the FBIOPUT_VSCREENINFO ioctl. If you want to pan
|
| 28 |
|
|
the screen only, you can use the FBIOPAN_DISPLAY ioctl.
|
| 29 |
|
|
|
| 30 |
|
|
- struct fb_cmap
|
| 31 |
|
|
|
| 32 |
|
|
Device independent colormap information. You can get and set the colormap
|
| 33 |
|
|
using the FBIOGETCMAP and FBIOPUTCMAP ioctls.
|
| 34 |
|
|
|
| 35 |
|
|
|
| 36 |
|
|
2. Inside the kernel
|
| 37 |
|
|
|
| 38 |
|
|
- struct fb_info
|
| 39 |
|
|
|
| 40 |
|
|
Generic information, API and low level information about a specific frame
|
| 41 |
|
|
buffer device instance (slot number, board address, ...).
|
| 42 |
|
|
|
| 43 |
|
|
- struct `par'
|
| 44 |
|
|
|
| 45 |
|
|
Device dependent information that uniquely defines the video mode for this
|
| 46 |
|
|
particular piece of hardware.
|
| 47 |
|
|
|
| 48 |
|
|
|
| 49 |
|
|
--------------------------------------------------------------------------------
|
| 50 |
|
|
|
| 51 |
|
|
*** VISUALS USED BY THE FRAME BUFFER DEVICE API ***
|
| 52 |
|
|
|
| 53 |
|
|
|
| 54 |
|
|
Monochrome (FB_VISUAL_MONO01 and FB_VISUAL_MONO10)
|
| 55 |
|
|
-------------------------------------------------
|
| 56 |
|
|
Each pixel is either black or white.
|
| 57 |
|
|
|
| 58 |
|
|
|
| 59 |
|
|
Pseudo color (FB_VISUAL_PSEUDOCOLOR and FB_VISUAL_STATIC_PSEUDOCOLOR)
|
| 60 |
|
|
---------------------------------------------------------------------
|
| 61 |
|
|
The whole pixel value is fed through a programmable lookup table that has one
|
| 62 |
|
|
color (including red, green, and blue intensities) for each possible pixel
|
| 63 |
|
|
value, and that color is displayed.
|
| 64 |
|
|
|
| 65 |
|
|
|
| 66 |
|
|
True color (FB_VISUAL_TRUECOLOR)
|
| 67 |
|
|
--------------------------------
|
| 68 |
|
|
The pixel value is broken up into red, green, and blue fields.
|
| 69 |
|
|
|
| 70 |
|
|
|
| 71 |
|
|
Direct color (FB_VISUAL_DIRECTCOLOR)
|
| 72 |
|
|
------------------------------------
|
| 73 |
|
|
The pixel value is broken up into red, green, and blue fields, each of which
|
| 74 |
|
|
are looked up in separate red, green, and blue lookup tables.
|
| 75 |
|
|
|
| 76 |
|
|
|
| 77 |
|
|
Grayscale displays
|
| 78 |
|
|
------------------
|
| 79 |
|
|
Grayscale and static grayscale are special variants of pseudo color and static
|
| 80 |
|
|
pseudo color, where the red, green and blue components are always equal to
|
| 81 |
|
|
each other.
|
| 82 |
|
|
|
