Adding upstream version 4.19.249.upstream/4.19.249upstream

Signed-off-by: Daniel Baumann <daniel.baumann@progress-linux.org>

1 files changed, 181 insertions, 0 deletions

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+
+What is vesafb?
+===============
+
+This is a generic driver for a graphic framebuffer on intel boxes.
+
+The idea is simple:  Turn on graphics mode at boot time with the help
+of the BIOS, and use this as framebuffer device /dev/fb0, like the m68k
+(and other) ports do.
+
+This means we decide at boot time whenever we want to run in text or
+graphics mode.  Switching mode later on (in protected mode) is
+impossible; BIOS calls work in real mode only.  VESA BIOS Extensions
+Version 2.0 are required, because we need a linear frame buffer.
+
+Advantages:
+
+ * It provides a nice large console (128 cols + 48 lines with 1024x768)
+   without using tiny, unreadable fonts.
+ * You can run XF68_FBDev on top of /dev/fb0 (=> non-accelerated X11
+   support for every VBE 2.0 compliant graphics board).
+ * Most important: boot logo :-)
+
+Disadvantages:
+
+ * graphic mode is slower than text mode...
+
+
+How to use it?
+==============
+
+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   
+32k |  0x110    0x113    0x116    0x119   
+64k |  0x111    0x114    0x117    0x11A   
+16M |  0x112    0x115    0x118    0x11B   
+
+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   
+32k |  0x310    0x313    0x316    0x319   
+64k |  0x311    0x314    0x317    0x31A   
+16M |  0x312    0x315    0x318    0x31B   
+
+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.
+
+X11
+===
+
+XF68_FBDev should work just fine, but it is non-accelerated.  Running
+another (accelerated) X-Server like XF86_SVGA might or might not work.
+It depends on X-Server and graphics board.
+
+The X-Server must restore the video mode correctly, else you end up
+with a broken console (and vesafb cannot do anything about this).
+
+
+Refresh rates
+=============
+
+There is no way to change the vesafb video mode and/or timings after
+booting linux.  If you are not happy with the 60 Hz refresh rate, you
+have these options:
+
+ * configure and load the DOS-Tools for the graphics board (if
+   available) and boot linux with loadlin.
+ * use a native driver (matroxfb/atyfb) instead if vesafb.  If none
+   is available, write a new one!
+ * VBE 3.0 might work too.  I have neither a gfx board with VBE 3.0
+   support nor the specs, so I have not checked this yet.
+
+
+Configuration
+=============
+
+The VESA BIOS provides protected mode interface for changing
+some parameters.  vesafb can use it for palette changes and
+to pan the display.  It is turned off by default because it
+seems not to work with some BIOS versions, but there are options
+to turn it on.
+
+You can pass options to vesafb using "video=vesafb:option" on
+the kernel command line.  Multiple options should be separated
+by comma, like this: "video=vesafb:ypan,invers"
+
+Accepted options:
+
+invers	no comment...
+
+ypan	enable display panning using the VESA protected mode 
+	interface.  The visible screen is just a window of the
+	video memory, console scrolling is done by changing the
+	start of the window.
+	pro:	* scrolling (fullscreen) is fast, because there is
+		  no need to copy around data.
+		* You'll get scrollback (the Shift-PgUp thing),
+		  the video memory can be used as scrollback buffer
+	kontra: * scrolling only parts of the screen causes some
+		  ugly flicker effects (boot logo flickers for
+		  example).
+
+ywrap	Same as ypan, but assumes your gfx board can wrap-around 
+	the video memory (i.e. starts reading from top if it
+	reaches the end of video memory).  Faster than ypan.
+
+redraw	scroll by redrawing the affected part of the screen, this
+	is the safe (and slow) default.
+
+
+vgapal	Use the standard vga registers for palette changes.
+	This is the default.
+pmipal	Use the protected mode interface for palette changes.
+
+mtrr:n	setup memory type range registers for the vesafb framebuffer
+	where n:
+	      0 - disabled (equivalent to nomtrr) (default)
+	      1 - uncachable
+	      2 - write-back
+	      3 - write-combining
+	      4 - write-through
+
+	If you see the following in dmesg, choose the type that matches the
+	old one. In this example, use "mtrr:2".
+...
+mtrr: type mismatch for e0000000,8000000 old: write-back new: write-combining
+...
+
+nomtrr  disable mtrr
+
+vremap:n
+        remap 'n' MiB of video RAM. If 0 or not specified, remap memory
+	according to video mode. (2.5.66 patch/idea by Antonino Daplas
+	reversed to give override possibility (allocate more fb memory
+	than the kernel would) to 2.4 by tmb@iki.fi)
+
+vtotal:n
+        if the video BIOS of your card incorrectly determines the total
+        amount of video RAM, use this option to override the BIOS (in MiB).
+
+Have fun!
+
+  Gerd
+
+--
+Gerd Knorr <kraxel@goldbach.in-berlin.de>
+
+Minor (mostly typo) changes 
+by Nico Schmoigl <schmoigl@rumms.uni-mannheim.de>