93 lines
3.9 KiB
HTML
93 lines
3.9 KiB
HTML
<!DOCTYPE HTML PUBLIC "-//W3C//DTD HTML 3.2 Final//EN">
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<HTML>
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<META NAME="GENERATOR" CONTENT="SGML-Tools 1.0.9">
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<TITLE>The Linux BootPrompt-HowTo: Boot Arguments for Video Frame Buffer Drivers</TITLE>
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<LINK HREF="BootPrompt-HOWTO-6.html" REL=next>
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<LINK HREF="BootPrompt-HOWTO-4.html" REL=previous>
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<LINK HREF="BootPrompt-HOWTO.html#toc5" REL=contents>
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</HEAD>
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<BODY>
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<A HREF="BootPrompt-HOWTO-6.html">Next</A>
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<A HREF="BootPrompt-HOWTO-4.html">Previous</A>
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<A HREF="BootPrompt-HOWTO.html#toc5">Contents</A>
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<HR>
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<H2><A NAME="s5">5. Boot Arguments for Video Frame Buffer Drivers</A></H2>
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<P>The `video=' argument (not avail. in v2.0 kernels)
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is used when the frame buffer device abstraction layer
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is built into the kernel. If that sounds complicated,
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well it isn't really too bad. It basically means that
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instead of having a different
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video program (the X11R6 server) for each brand of video
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card (e.g. XF86_S3, XF86_SVGA, ...), the kernel would have
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a built in driver available for each video card and export
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a single interface for the video program so that only one
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X11R6 server (XF86_FBDev) would be required. This is similar
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to how networking is now - the kernel has drivers available for
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each brand of network card and exports a single network
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interface so that just one version of a network program
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(like Netscape) will work for all systems, regardless of the
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underlying brand of network card.
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<P>The typical format of this argument is
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<CODE>video=name:option1,option2,...</CODE>
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where <CODE>name</CODE> is the name of a generic option or of a
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frame buffer driver.
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The <CODE>video=</CODE> option is passed from <CODE>linux/init/main.c</CODE>
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into <CODE>linux/drivers/video/fbmem.c</CODE> for further processing.
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Here it is checked for some generic options before trying to
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match to a known driver name. Once a driver name match is made,
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the comma separated option list is then passed into that particular
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driver for final processing. The list of valid driver names
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can be found by reading down the <CODE>fb_drivers</CODE> array in the
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file <CODE>fbmem.c</CODE> mentioned above.
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<P>Information on the options that each driver supports will
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eventually be found in <CODE>linux/Documentation/fb/</CODE> but
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currently (v2.2) only a few are described there.
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Unfortunately the number
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of video drivers and the number of options for each one
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is content for another document itself and hence
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too much to list here.
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<P>If there is no Documentation file for your card, you
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will have to get
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the option information directly from the driver. Go to
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<CODE>linux/drivers/video/</CODE> and look in the appropriate
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<CODE>???fb.c</CODE> file (the ??? will be based on the card name).
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In there, search for a function with <CODE>_setup</CODE> in its name
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and you should see what options the driver tries to match,
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such as <CODE>font</CODE> or <CODE>mode</CODE> or...
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<P>
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<H2><A NAME="ss5.1">5.1 The `video=map:...' Argument</A>
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</H2>
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<P>This option is used to set/override the console to frame buffer
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device mapping. A comma separated list of numbers sets the mapping,
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with the value of option N taken to be the frame buffer device
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number for console N.
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<P>
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<H2><A NAME="ss5.2">5.2 The `video=scrollback:...' Argument</A>
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</H2>
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<P>A number after the colon will set the size of memory allocated
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for the scrollback buffer. (Use Shift and Page Up or Page Down
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keys to scroll.) A suffix of `k' or `K' after the number will
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indicate that the number is to be interpreted as kilobytes
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instead of bytes.
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<P>
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<H2><A NAME="ss5.3">5.3 The `video=vc:...' Argument</A>
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</H2>
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<P>
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<P>A number, or a range of numbers (e.g. <CODE>video=vc:2-5</CODE>)
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will specify the first, or the first and last frame
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buffer virtual console(s). The use of this option also
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has the effect of setting the frame buffer console to
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<EM>not</EM> be the default console.
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<P>
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<HR>
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<A HREF="BootPrompt-HOWTO-6.html">Next</A>
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<A HREF="BootPrompt-HOWTO-4.html">Previous</A>
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<A HREF="BootPrompt-HOWTO.html#toc5">Contents</A>
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