patch-2.3.14 linux/Documentation/fb/modedb.txt

• Lines: 49
• Date: Wed Aug 18 10:10:06 1999
• Orig file: v2.3.13/linux/Documentation/fb/modedb.txt
• Orig date: Wed Dec 31 16:00:00 1969

diff -u --recursive --new-file v2.3.13/linux/Documentation/fb/modedb.txt linux/Documentation/fb/modedb.txt
@@ -0,0 +1,48 @@
+
+
+			modedb default video mode support
+
+
+Currently all frame buffer device drivers have their own video mode databases,
+which is a mess and a waste of resources. The main idea of modedb is to have
+
+  - one routine to probe for video modes, which can be used by all frame buffer
+    devices
+  - one generic video mode database with a fair amount of standard videomodes
+    (taken from XFree86)
+  - the possibility to supply your own mode database for graphics hardware that
+    needs non-standard modes, like amifb and Mac frame buffer drivers (which
+    use macmodes.c)
+
+When a frame buffer device receives a video= option it doesn't know, it should
+consider that to be a video mode option. If no frame buffer device is specified
+in a video= option, fbmem considers that to be a global video mode option.
+
+Valid mode specifiers (mode_option argument):
+
+    <xres>x<yres>[-<bpp>][@<refresh>]
+    <name>[-<bpp>][@<refresh>]
+
+with <xres>, <yres>, <bpp> and <refresh> decimal numbers and <name> a string.
+Things between square brackets are optional.
+
+To find a suitable video mode, you just call
+
+int __init fb_find_mode(struct fb_var_screeninfo *var,
+                        struct fb_info *info, const char *mode_option,
+                        const struct fb_videomode *db, unsigned int dbsize,
+                        const struct fb_videomode *default_mode,
+                        unsigned int default_bpp)
+
+with db/dbsize your non-standard video mode database, or NULL to use the
+standard video mode database.
+
+fb_find_mode() first tries the specified video mode (or any mode that matches,
+e.g. there can be multiple 640x480 modes, each of them is tried). If that
+fails, the default mode is tried. If that fails, it walks over all modes.
+
+BTW, only a few drivers use this at the moment. Others are to follow
+(feel free to send patches).
+
+
+