--- /dev/null
+CyBlaFB is a framebuffer driver for the Cyberblade/i1 graphics core integrated
+into the VIA Apollo PLE133 (aka vt8601) south bridge. It is developed and
+tested using a VIA EPIA 5000 board.
+
+Cyblafb - compiled into the kernel or as a module?
+==================================================
+
+You might compile cyblafb either as a module or compile it permanently into the
+kernel.
+
+Unless you have a real reason to do so you should not compile both vesafb and
+cyblafb permanently into the kernel. It's possible and it helps during the
+developement cycle, but it's useless and will at least block some otherwise
+usefull memory for ordinary users.
+
+Selecting Modes
+===============
+
+ Startup Mode
+ ============
+
+ First of all, you might use the "vga=???" boot parameter as it is
+ documented in vesafb.txt and svga.txt. Cyblafb will detect the video
+ mode selected and will use the geometry and timings found by
+ inspecting the hardware registers.
+
+ video=cyblafb vga=0x317
+
+ Alternatively you might use a combination of the mode, ref and bpp
+ parameters. If you compiled the driver into the kernel, add something
+ like this to the kernel command line:
+
+ video=cyblafb:1280x1024,bpp=16,ref=50 ...
+
+ If you compiled the driver as a module, the same mode would be
+ selected by the following command:
+
+ modprobe cyblafb mode=1280x1024 bpp=16 ref=50 ...
+
+ None of the modes possible to select as startup modes are affected by
+ the problems described at the end of the next subsection.
+
+ For all startup modes cyblafb chooses a virtual x resolution of 2048,
+ the only exception is mode 1280x1024 in combination with 32 bpp. This
+ allows ywrap scrolling for all those modes if rotation is 0 or 2, and
+ also fast scrolling if rotation is 1 or 3. The default virtual y reso-
+ lution is 4096 for bpp == 8, 2048 for bpp==16 and 1024 for bpp == 32,
+ again with the only exception of 1280x1024 at 32 bpp.
+
+ Please do set your video memory size to 8 Mb in the Bios setup. Other
+ values will work, but performace is decreased for a lot of modes.
+
+ Mode changes using fbset
+ ========================
+
+ You might use fbset to change the video mode, see "man fbset". Cyblafb
+ generally does assume that you know what you are doing. But it does
+ some checks, especially those that are needed to prevent you from
+ damaging your hardware.
+
+ - only 8, 16, 24 and 32 bpp video modes are accepted
+ - interlaced video modes are not accepted
+ - double scan video modes are not accepted
+ - if a flat panel is found, cyblafb does not allow you
+ to program a resolution higher than the physical
+ resolution of the flat panel monitor
+ - cyblafb does not allow vclk to exceed 230 MHz. As 32 bpp
+ and (currently) 24 bit modes use a doubled vclk internally,
+ the dotclock limit as seen by fbset is 115 MHz for those
+ modes and 230 MHz for 8 and 16 bpp modes.
+ - cyblafb will allow you to select very high resolutions as
+ long as the hardware can be programmed to these modes. The
+ documented limit 1600x1200 is not enforced, but don't expect
+ perfect signal quality.
+
+ Any request that violates the rules given above will be either changed
+ to something the hardware supports or an error value will be returned.
+
+ If you program a virtual y resolution higher than the hardware limit,
+ cyblafb will silently decrease that value to the highest possible
+ value. The same is true for a virtual x resolution that is not
+ supported by the hardware. Cyblafb tries to adapt vyres first because
+ vxres decides if ywrap scrolling is possible or not.
+
+ Attempts to disable acceleration are ignored, I believe that this is
+ safe.
+
+ Some video modes that should work do not work as expected. If you use
+ the standard fb.modes, fbset 640x480-60 will program that mode, but
+ you will see a vertical area, about two characters wide, with only
+ much darker characters than the other characters on the screen.
+ Cyblafb does allow that mode to be set, as it does not violate the
+ official specifications. It would need a lot of code to reliably sort
+ out all invalid modes, playing around with the margin values will
+ give a valid mode quickly. And if cyblafb would detect such an invalid
+ mode, should it silently alter the requested values or should it
+ report an error? Both options have some pros and cons. As stated
+ above, none of the startup modes are affected, and if you set
+ verbosity to 1 or higher, cyblafb will print the fbset command that
+ would be needed to program that mode using fbset.
+
+
+Other Parameters
+================
+
+
+crt don't autodetect, assume monitor connected to
+ standard VGA connector
+
+fp don't autodetect, assume flat panel display
+ connected to flat panel monitor interface
+
+nativex inform driver about native x resolution of
+ flat panel monitor connected to special
+ interface (should be autodetected)
+
+stretch stretch image to adapt low resolution modes to
+ higer resolutions of flat panel monitors
+ connected to special interface
+
+center center image to adapt low resolution modes to
+ higer resolutions of flat panel monitors
+ connected to special interface
+
+memsize use if autodetected memsize is wrong ...
+ should never be necessary
+
+nopcirr disable PCI read retry
+nopciwr disable PCI write retry
+nopcirb disable PCI read bursts
+nopciwb disable PCI write bursts
+
+bpp bpp for specified modes
+ valid values: 8 || 16 || 24 || 32
+
+ref refresh rate for specified mode
+ valid values: 50 <= ref <= 85
+
+mode 640x480 or 800x600 or 1024x768 or 1280x1024
+ if not specified, the startup mode will be detected
+ and used, so you might also use the vga=??? parameter
+ described in vesafb.txt. If you do not specify a mode,
+ bpp and ref parameters are ignored.
+
+verbosity 0 is the default, increase to at least 2 for every
+ bug report!
+
+Development hints
+=================
+
+It's much faster do compile a module and to load the new version after
+unloading the old module than to compile a new kernel and to reboot. So if you
+try to work on cyblafb, it might be a good idea to use cyblafb as a module.
+In real life, fast often means dangerous, and that's also the case here. If
+you introduce a serious bug when cyblafb is compiled into the kernel, the
+kernel will lock or oops with a high probability before the file system is
+mounted, and the danger for your data is low. If you load a broken own version
+of cyblafb on a running system, the danger for the integrity of the file
+system is much higher as you might need a hard reset afterwards. Decide
+yourself.
+
+Module unloading, the vfb method
+================================
+
+If you want to unload/reload cyblafb using the virtual framebuffer, you need
+to enable vfb support in the kernel first. After that, load the modules as
+shown below:
+
+ modprobe vfb vfb_enable=1
+ modprobe fbcon
+ modprobe cyblafb
+ fbset -fb /dev/fb1 1280x1024-60 -vyres 2662
+ con2fb /dev/fb1 /dev/tty1
+ ...
+
+If you now made some changes to cyblafb and want to reload it, you might do it
+as show below:
+
+ con2fb /dev/fb0 /dev/tty1
+ ...
+ rmmod cyblafb
+ modprobe cyblafb
+ con2fb /dev/fb1 /dev/tty1
+ ...
+
+Of course, you might choose another mode, and most certainly you also want to
+map some other /dev/tty* to the real framebuffer device. You might also choose
+to compile fbcon as a kernel module or place it permanently in the kernel.
+
+I do not know of any way to unload fbcon, and fbcon will prevent the
+framebuffer device loaded first from unloading. [If there is a way, then
+please add a description here!]
+
+Module unloading, the vesafb method
+===================================
+
+Configure the kernel:
+
+ <*> Support for frame buffer devices
+ [*] VESA VGA graphics support
+ <M> Cyberblade/i1 support
+
+Add e.g. "video=vesafb:ypan vga=0x307" to the kernel parameters. The ypan
+parameter is important, choose any vga parameter you like as long as it is
+a graphics mode.
+
+After booting, load cyblafb without any mode and bpp parameter and assign
+cyblafb to individual ttys using con2fb, e.g.:
+
+ modprobe cyblafb
+ con2fb /dev/fb1 /dev/tty1
+
+Unloading cyblafb works without problems after you assign vesafb to all
+ttys again, e.g.:
+
+ con2fb /dev/fb0 /dev/tty1
+ rmmod cyblafb
git://git.onelab.eu / linux-2.6.git / blobdiff