linux中Framebuffer的配置及應(yīng)用

借助于framebuffer，我們能夠在console下面作很多事情。首先下載framebuffer的配置工具fbset:
# apt-get install fbset 下載完畢后，配置文件/etc/fb.modes隨之產(chǎn)生。

比較簡(jiǎn)單的作法是用萬(wàn)能的vesafb，如果它被編譯進(jìn)了內(nèi)核，如：
Device Drivers -> Graphics support ->

?VESA VGA graphics support
那么在grub內(nèi)核引導(dǎo)那一行的后面加上vga=791 它的含義是VESA framebuffer console @ 1024x768x64k，進(jìn)入系統(tǒng)后可以直接使用framebuffer，看一下這種情況下的各項(xiàng)數(shù)據(jù)：
# fbset -s
mode "1024x768-76"
??? # D: 78.653 MHz, H: 59.949 kHz, V: 75.694 Hz
??? geometry 1024 768 1024 768 16
??? timings 12714 128 32 16 4 128 4
??? rgba 5/11,6/5,5/0,0/0
endmode

用具體顯卡的framebuffer驅(qū)動(dòng)是另一種選擇，拿Nvidia顯卡為例，Nvidia顯卡的xorg驅(qū)動(dòng)模塊與其framebuffer的驅(qū)動(dòng)模塊是互相排斥的，如果要用一個(gè)就必須清除另一個(gè)：
# rmmod nvidia
裝載nvidia的framebuffer驅(qū)動(dòng)：
# modprobe nvidiafb
裝載成功的時(shí)候，會(huì)產(chǎn)生/dev/fb0設(shè)備，console屏幕上的字體會(huì)有變化。
看一下當(dāng)前的配置：
# fbset -s
mode "1024x768-85"
??? # D: 94.500 MHz, H: 68.677 kHz, V: 84.997 Hz
??? geometry 1024 768 1024 32767 8
??? timings 10582 208 48 36 1 96 3
??? hsync high
??? vsync high
??? accel true
??? rgba 8/0,8/0,8/0,0/0
endmode

需要改變一下geometry及色深：
# fbset -g 1024 768 1024 768 32
# fbset -s
mode "1024x768-85"
??? # D: 94.500 MHz, H: 68.677 kHz, V: 84.997 Hz
??? geometry 1024 768 1024 768 32
??? timings 10582 208 48 36 1 96 3
??? hsync high
??? vsync high
??? accel true
??? rgba 8/16,8/8,8/0,8/24
endmode

我們把它與使用VESA ramebuffer后的數(shù)據(jù)比較一下,顯然，根據(jù)具體的顯卡來(lái)驅(qū)動(dòng)framebuffer可以在顏色上達(dá)到最佳值，好，現(xiàn)在我們?cè)赾onsole下面能夠作的事情：
一、視頻播放，可以用mplayer 或者 fbxine：
# mplayer -vo fbdev -vf scale=1024:768 video_file.avi
-vo fbdev 是告訴mplayer用framebuffer作視頻驅(qū)動(dòng).
-vf scale=1024:768 是全屏的方法，可按屏幕的具體情況作調(diào)整
用fbxine的話需要下載：
# apt-get install xine-console
二、圖片文件與pdf文件瀏覽：
# apt-get install fbi
用這個(gè)軟件包里的fbi可以瀏覽圖片，fbgs可以觀看pdf文件：
# fbi -a *jpg
# fbgs -c *pdf
三、中文顯示：
# apt-get install jfbterm
# jfbterm
中文顯示的效果完美。

?

在內(nèi)核Documentation/fb/vesafb.txt文件中,有如下vesa-framebuffer的說(shuō)明
Switching modes is done using the vga=... boot parameter. Read
Documentation/svga.txt for details.
You should compile in both vgacon (for text mode) and vesafb (for
graphics mode). Which of them takes over the console depends on
whenever the specified mode is text or graphics.
The graphic modes are NOT in the list which you get if you boot with
vga=ask and hit return. The mode you wish to use is derived from the
VESA mode number. Here are those VESA mode numbers:
| 640x480 800x600 1024x768 1280x1024
----+-------------------------------------
256 | 0x101 0x103 0x105 0x107 8位色
32k | 0x110 0x113 0x116 0x119 15位色
64k | 0x111 0x114 0x117 0x11A 16位色
16M | 0x112 0x115 0x118 0x11B 24位色
The video mode number of the Linux kernel is the VESA mode number plus
0x200.
Linux_kernel_mode_number = VESA_mode_number + 0x200
So the table for the Kernel mode numbers are:
| 640x480 800x600 1024x768 1280x1024
----+-------------------------------------
256 | 0x301 0x303 0x305 0x307 8位色
32k | 0x310 0x313 0x316 0x319 15位色
64k | 0x311 0x314 0x317 0x31A 16位色
16M | 0x312 0x315 0x318 0x31B 24位色
To enable one of those modes you have to specify "vga=ask" in the
lilo.conf file and rerun LILO. Then you can type in the desired
mode at the "vga=ask" prompt. For example if you like to use
1024x768x256 colors you have to say "305" at this prompt.
If this does not work, this might be because your BIOS does not support
linear framebuffers or because it does not support this mode at all.
Even if your board does, it might be the BIOS which does not. VESA BIOS
Extensions v2.0 are required, 1.2 is NOT sufficient. You will get a
"bad mode number" message if something goes wrong.
1. Note: LILO cannot handle hex, for booting directly with
"vga=mode-number" you have to transform the numbers to decimal.
2. Note: Some newer versions of LILO appear to work with those hex values,
if you set the 0x in front of the numbers.