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62 lines
2.4 KiB
Text
62 lines
2.4 KiB
Text
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modedb default video mode support
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Currently all frame buffer device drivers have their own video mode databases,
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which is a mess and a waste of resources. The main idea of modedb is to have
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- one routine to probe for video modes, which can be used by all frame buffer
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devices
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- one generic video mode database with a fair amount of standard videomodes
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(taken from XFree86)
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- the possibility to supply your own mode database for graphics hardware that
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needs non-standard modes, like amifb and Mac frame buffer drivers (which
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use macmodes.c)
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When a frame buffer device receives a video= option it doesn't know, it should
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consider that to be a video mode option. If no frame buffer device is specified
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in a video= option, fbmem considers that to be a global video mode option.
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Valid mode specifiers (mode_option argument):
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<xres>x<yres>[-<bpp>][@<refresh>]
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<name>[-<bpp>][@<refresh>]
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with <xres>, <yres>, <bpp> and <refresh> decimal numbers and <name> a string.
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Things between square brackets are optional.
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To find a suitable video mode, you just call
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int __init fb_find_mode(struct fb_var_screeninfo *var,
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struct fb_info *info, const char *mode_option,
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const struct fb_videomode *db, unsigned int dbsize,
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const struct fb_videomode *default_mode,
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unsigned int default_bpp)
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with db/dbsize your non-standard video mode database, or NULL to use the
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standard video mode database.
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fb_find_mode() first tries the specified video mode (or any mode that matches,
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e.g. there can be multiple 640x480 modes, each of them is tried). If that
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fails, the default mode is tried. If that fails, it walks over all modes.
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To specify a video mode at bootup, use the following boot options:
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video=<driver>:<xres>x<yres>[-<bpp>][@refresh]
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where <driver> is a name from the table below. Valid default modes can be
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found in linux/drivers/video/modedb.c. Check your driver's documentation.
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There may be more modes.
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Drivers that support modedb boot options
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Boot Name Cards Supported
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amifb - Amiga chipset frame buffer
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aty128fb - ATI Rage128 / Pro frame buffer
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atyfb - ATI Mach64 frame buffer
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tdfxfb - 3D Fx frame buffer
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tridentfb - Trident (Cyber)blade chipset frame buffer
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BTW, only a few drivers use this at the moment. Others are to follow
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(feel free to send patches).
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