📄 00-index、framebuffer_txt、internals_txt译文 - ～ 悠悠风信子 ～ - csdnblog.htm
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<P
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align=center><SPAN><FONT color=#ff0000
size=5><STRONG> </STRONG><FONT
color=#000000>
</FONT><SPAN><SPAN><STRONG>文件00-INDEX译文</STRONG></SPAN></SPAN></FONT></SPAN>
<P
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align=center><STRONG><SPAN><FONT color=#ff0000
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framebuffer.txt译文</FONT></SPAN></STRONG></P>
<P
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align=left><STRONG><SPAN>1.</SPAN></STRONG><STRONG><SPAN>用户角度的<SPAN>/dev/fb*</SPAN></SPAN></STRONG></P>
<P
style="MARGIN: 0cm 0cm 0pt; TEXT-ALIGN: left; mso-pagination: widow-orphan"
align=left><SPAN>从用户的角度看，帧缓冲设备和其他位于<SPAN>/dev</SPAN>下面的设备类似。他是一个字符设备，通常<SPAN></SPAN></SPAN></P>
<P
style="MARGIN: 0cm 0cm 0pt; TEXT-ALIGN: left; mso-pagination: widow-orphan"
align=left><SPAN>主设备号是<SPAN>29</SPAN>，次设备号定义帧缓冲的个数。<SPAN></SPAN></SPAN></P>
<P
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align=left><SPAN></SPAN> </P>
<P
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align=left><SPAN>通常，使用如下方式（前面的数字代码次设备号）<SPAN></SPAN></SPAN></P>
<P
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align=left><SPAN><SPAN> </SPAN><SPAN> </SPAN>0 = /dev/fb0<SPAN> </SPAN>First frame buffer<BR><SPAN> </SPAN>1 = /dev/fb1<SPAN> </SPAN>Second frame buffer<BR><SPAN> </SPAN><SPAN> </SPAN>...<BR><SPAN> </SPAN>31 = /dev/fb31<SPAN> </SPAN>32nd frame buffer</SPAN></P>
<P
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align=left><SPAN><SPAN> </SPAN></SPAN></P>
<P
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align=left><SPAN>考虑到向下兼容，你可以创建符号链接：<SPAN></SPAN></SPAN></P>
<P
style="MARGIN: 0cm 0cm 0pt; TEXT-ALIGN: left; mso-pagination: widow-orphan"
align=left><SPAN><SPAN> </SPAN>/dev/fb0current -> fb0<BR><SPAN> </SPAN>/dev/fb1current -> fb1<BR><BR>and so on...</SPAN></P>
<P
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align=left><SPAN></SPAN> </P>
<P
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align=left><SPAN>帧缓冲设备也是一种普通的内存设备，你可以读写其内容。例如，对屏幕抓屏：<SPAN></SPAN></SPAN></P>
<P
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align=left><SPAN><SPAN> </SPAN>cp /dev/fb0 myfile<BR><BR></SPAN><SPAN>你也可以同时有多个显示设备，例如你的主板上出了内置的显卡还有另一独立的<SPAN></SPAN></SPAN></P>
<P
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align=left><SPAN>显卡。对应的帧缓冲设备<SPAN>(/dev/fb0 and /dev/fb1 etc.)</SPAN>可以独立工作。<SPAN></SPAN></SPAN></P>
<P
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align=left><SPAN></SPAN> </P>
<P
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align=left><SPAN>应用程序如<SPAN> X server</SPAN>一般使用<SPAN>/dev/fb0</SPAN>作为默认的显示帧缓冲区。你可以自定<SPAN></SPAN></SPAN></P>
<P
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align=left><SPAN>把某个设备作为默认的帧缓冲设备，设置<SPAN>$FRAMEBUFFER</SPAN>环境变量即可。在<SPAN>sh/bash</SPAN>：<SPAN></SPAN></SPAN></P>
<P
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align=left><SPAN><SPAN> </SPAN>export FRAMEBUFFER=/dev/fb1<BR><BR></SPAN><SPAN>在<SPAN>csh</SPAN>中：<SPAN><BR><BR><SPAN> </SPAN>setenv FRAMEBUFFER /dev/fb1</SPAN></SPAN></P>
<P
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align=left><SPAN><SPAN> </SPAN></SPAN></P>
<P
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align=left><SPAN>设定后，<SPAN>X server</SPAN>将使用第二个帧缓冲区设备。<SPAN></SPAN></SPAN></P>
<P
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align=left><SPAN></SPAN> </P>
<P
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align=left><STRONG><SPAN>2.</SPAN></STRONG><STRONG><SPAN>程序员角度看<SPAN>/dev/fb*</SPAN></SPAN></STRONG></P>
<P
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align=left><SPAN>正如你所知，一个帧缓冲设备和内存设备类似<SPAN>/dev/mem</SPAN>，并且有许多共性。你可以<SPAN></SPAN></SPAN></P>
<P
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align=left><SPAN>read,write,seek</SPAN><SPAN>以及<SPAN>mmap()</SPAN>。不同仅仅是帧缓冲的内存不是所有的内存区，而是显卡<SPAN></SPAN></SPAN></P>
<P
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align=left><SPAN>专用的那部分内存。<SPAN></SPAN></SPAN></P>
<P
style="MARGIN: 0cm 0cm 0pt; TEXT-ALIGN: left; mso-pagination: widow-orphan"
align=left><SPAN></SPAN> </P>
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