[PATCH] framebuffer: new driver for cyberblade/i1 graphics core

This is a framebuffer driver for the Cyberblade/i1 graphics core.

Currently tridenfb claims to support the cyberblade/i1 graphics core.  This
is of very limited truth.  Even vesafb is faster and provides more working
modes and a much better quality of the video signal.  There is a great
number of bugs in tridentfb ...  but most often it is impossible to decide
if these bugs are real bugs or if fixing them for the cyberblade/i1 core
would break support for one of the other supported chips.

Tridentfb seems to be unmaintained,and documentation for most of the
supported chips is not available.  So "fixing" cyberblade/i1 support inside
of tridentfb was not an option, it would have caused numerous
if(CYBERBLADEi1) else ...  cases and would have rendered the code to be
almost unmaintainable.

A first version of this driver was published on 2005-07-31.  A fix for a
bug reported by Jochen Hein was integrated as well as some changes
requested by Antonino A.  Daplas.

A message has been added to tridentfb to inform current users of tridentfb
to switch to cyblafb if the cyberblade/i1 graphics core is detected.

This patch is one logical change, but because of the included documentation
it is bigger than 70kb.  Therefore it is not sent to lkml and
linux-fbdev-devel,

Signed-off-by: Knut Petersen <Knut_Petersen@t-online.de>
Cc: Muli Ben-Yehuda <mulix@mulix.org>
Acked-by: Antonino Daplas <adaplas@pol.net>
Signed-off-by: Andrew Morton <akpm@osdl.org>
Signed-off-by: Linus Torvalds <torvalds@osdl.org>

8 files changed, 596 insertions, 0 deletions

diff --git a/Documentation/fb/cyblafb/bugs b/Documentation/fb/cyblafb/bugs
new file mode 100644
index 000000000000..f90cc66ea919
--- /dev/null
+++ b/Documentation/fb/cyblafb/bugs
@@ -0,0 +1,14 @@
+Bugs
+====
+
+I currently don't know of any bug. Please do send reports to:
+ - linux-fbdev-devel@lists.sourceforge.net
+ - Knut_Petersen@t-online.de.
+
+
+Untested features
+=================
+
+All LCD stuff is untested. If it worked in tridentfb, it should work in
+cyblafb. Please test and report the results to Knut_Petersen@t-online.de.
+
diff --git a/Documentation/fb/cyblafb/credits b/Documentation/fb/cyblafb/credits
new file mode 100644
index 000000000000..0eb3b443dc2b
--- /dev/null
+++ b/Documentation/fb/cyblafb/credits
@@ -0,0 +1,7 @@
+Thanks to
+=========
+   *    Alan Hourihane, for writing the X trident driver
+   *    Jani Monoses, for writing the tridentfb driver
+   *    Antonino A. Daplas, for review of the first published
+        version of cyblafb and some code
+   *    Jochen Hein, for testing and a helpfull bug report
diff --git a/Documentation/fb/cyblafb/documentation b/Documentation/fb/cyblafb/documentation
new file mode 100644
index 000000000000..bb1aac048425
--- /dev/null
+++ b/Documentation/fb/cyblafb/documentation
@@ -0,0 +1,17 @@
+Available Documentation
+=======================
+
+Apollo PLE 133 Chipset VT8601A North Bridge Datasheet, Rev. 1.82, October 22,
+2001, available from VIA:
+
+        http://www.viavpsd.com/product/6/15/DS8601A182.pdf
+
+The datasheet is incomplete, some registers that need to be programmed are not
+explained at all and important bits are listed as "reserved". But you really
+need the datasheet to understand the code.  "p. xxx" comments refer to page
+numbers of this document.
+
+XFree/XOrg drivers are available and of good quality, looking at the code
+there is a good idea if the datasheet does not provide enough information
+or if the datasheet seems to be wrong.
+
diff --git a/Documentation/fb/cyblafb/fb.modes b/Documentation/fb/cyblafb/fb.modes
new file mode 100644
index 000000000000..cf4351fc32ff
--- /dev/null
+++ b/Documentation/fb/cyblafb/fb.modes
@@ -0,0 +1,155 @@
+#
+#   Sample fb.modes file
+#
+#       Provides an incomplete list of working modes for
+#       the cyberblade/i1 graphics core.
+#
+#       The value 4294967256 is used instead of -40. Of course, -40 is not
+#       a really reasonable value, but chip design does not always follow
+#       logic. Believe me, it's ok, and it's the way the BIOS does it.
+#
+#       fbset requires 4294967256 in fb.modes and -40 as an argument to
+#       the -t parameter. That's also not too reasonable, and it might change
+#       in the future or might even be differt for your current version.
+#
+
+mode "640x480-50"
+    geometry 640 480 640 3756 8
+    timings 47619 4294967256 24 17 0 216 3
+endmode
+
+mode "640x480-60"
+    geometry 640 480 640 3756 8
+    timings 39682 4294967256 24 17 0 216 3
+endmode
+
+mode "640x480-70"
+    geometry 640 480 640 3756 8
+    timings 34013 4294967256 24 17 0 216 3
+endmode
+
+mode "640x480-72"
+    geometry 640 480 640 3756 8
+    timings 33068 4294967256 24 17 0 216 3
+endmode
+
+mode "640x480-75"
+    geometry 640 480 640 3756 8
+    timings 31746 4294967256 24 17 0 216 3
+endmode
+
+mode "640x480-80"
+    geometry 640 480 640 3756 8
+    timings 29761 4294967256 24 17 0 216 3
+endmode
+
+mode "640x480-85"
+    geometry 640 480 640 3756 8
+    timings 28011 4294967256 24 17 0 216 3
+endmode
+
+mode "800x600-50"
+    geometry 800 600 800 3221 8
+    timings 30303 96 24 14 0 136 11
+endmode
+
+mode "800x600-60"
+    geometry 800 600 800 3221 8
+    timings 25252 96 24 14 0 136 11
+endmode
+
+mode "800x600-70"
+    geometry 800 600 800 3221 8
+    timings 21645 96 24 14 0 136 11
+endmode
+
+mode "800x600-72"
+    geometry 800 600 800 3221 8
+    timings 21043 96 24 14 0 136 11
+endmode
+
+mode "800x600-75"
+    geometry 800 600 800 3221 8
+    timings 20202 96 24 14 0 136 11
+endmode
+
+mode "800x600-80"
+    geometry 800 600 800 3221 8
+    timings 18939 96 24 14 0 136 11
+endmode
+
+mode "800x600-85"
+    geometry 800 600 800 3221 8
+    timings 17825 96 24 14 0 136 11
+endmode
+
+mode "1024x768-50"
+    geometry 1024 768 1024 2815 8
+    timings 19054 144 24 29 0 120 3
+endmode
+
+mode "1024x768-60"
+    geometry 1024 768 1024 2815 8
+    timings 15880 144 24 29 0 120 3
+endmode
+
+mode "1024x768-70"
+    geometry 1024 768 1024 2815 8
+    timings 13610 144 24 29 0 120 3
+endmode
+
+mode "1024x768-72"
+    geometry 1024 768 1024 2815 8
+    timings 13232 144 24 29 0 120 3
+endmode
+
+mode "1024x768-75"
+    geometry 1024 768 1024 2815 8
+    timings 12703 144 24 29 0 120 3
+endmode
+
+mode "1024x768-80"
+    geometry 1024 768 1024 2815 8
+    timings 11910 144 24 29 0 120 3
+endmode
+
+mode "1024x768-85"
+    geometry 1024 768 1024 2815 8
+    timings 11209 144 24 29 0 120 3
+endmode
+
+mode "1280x1024-50"
+    geometry 1280 1024 1280 2662 8
+    timings 11114 232 16 39 0 160 3
+endmode
+
+mode "1280x1024-60"
+    geometry 1280 1024 1280 2662 8
+    timings 9262 232 16 39 0 160 3
+endmode
+
+mode "1280x1024-70"
+    geometry 1280 1024 1280 2662 8
+    timings 7939 232 16 39 0 160 3
+endmode
+
+mode "1280x1024-72"
+    geometry 1280 1024 1280 2662 8
+    timings 7719 232 16 39 0 160 3
+endmode
+
+mode "1280x1024-75"
+    geometry 1280 1024 1280 2662 8
+    timings 7410 232 16 39 0 160 3
+endmode
+
+mode "1280x1024-80"
+    geometry 1280 1024 1280 2662 8
+    timings 6946 232 16 39 0 160 3
+endmode
+
+mode "1280x1024-85"
+    geometry 1280 1024 1280 2662 8
+    timings 6538 232 16 39 0 160 3
+endmode
+
diff --git a/Documentation/fb/cyblafb/performance b/Documentation/fb/cyblafb/performance
new file mode 100644
index 000000000000..eb4e47a9cea6
--- /dev/null
+++ b/Documentation/fb/cyblafb/performance
@@ -0,0 +1,80 @@
+Speed
+=====
+
+CyBlaFB is much faster than tridentfb and vesafb. Compare the performance data
+for mode 1280x1024-[8,16,32]@61 Hz.
+
+Test 1: Cat a file with 2000 lines of 0 characters.
+Test 2: Cat a file with 2000 lines of 80 characters.
+Test 3: Cat a file with 2000 lines of 160 characters.
+
+All values show system time use in seconds, kernel 2.6.12 was used for
+the measurements. 2.6.13 is a bit slower, 2.6.14 hopefully will include a
+patch that speeds up kernel bitblitting a lot ( > 20%).
+
++-----------+-----------------------------------------------------+
+|           |                   not accelerated                   |
+| TRIDENTFB +-----------------+-----------------+-----------------+
+| of 2.6.12 |      8 bpp      |     16 bpp      |     32 bpp      |
+|           | noypan |   ypan | noypan |   ypan | noypan |   ypan |
++-----------+--------+--------+--------+--------+--------+--------+
+|    Test 1 |   4.31 |   4.33 |   6.05 |  12.81 |  ----  |  ----  |
+|    Test 2 |  67.94 |   5.44 | 123.16 |  14.79 |  ----  |  ----  |
+|    Test 3 | 131.36 |   6.55 | 240.12 |  16.76 |  ----  |  ----  |
++-----------+--------+--------+--------+--------+--------+--------+
+|  Comments |                 |                 | completely bro- |
+|           |                 |                 | ken, monitor    |
+|           |                 |                 | switches off    |
++-----------+-----------------+-----------------+-----------------+
+
+
++-----------+-----------------------------------------------------+
+|           |                     accelerated                     |
+| TRIDENTFB +-----------------+-----------------+-----------------+
+| of 2.6.12 |      8 bpp      |     16 bpp      |     32 bpp      |
+|           | noypan |   ypan | noypan |   ypan | noypan |   ypan |
++-----------+--------+--------+--------+--------+--------+--------+
+|    Test 1 |  ----  |  ----  |  20.62 |   1.22 |  ----  |  ----  |
+|    Test 2 |  ----  |  ----  |  22.61 |   3.19 |  ----  |  ----  |
+|    Test 3 |  ----  |  ----  |  24.59 |   5.16 |  ----  |  ----  |
++-----------+--------+--------+--------+--------+--------+--------+
+|  Comments | broken, writing | broken, ok only | completely bro- |
+|           | to wrong places | if bgcolor is   | ken, monitor    |
+|           | on screen + bug | black, bug in   | switches off    |
+|           | in fillrect()   | fillrect()      |                 |
++-----------+-----------------+-----------------+-----------------+
+
+
++-----------+-----------------------------------------------------+
+|           |                   not accelerated                   |
+|   VESAFB  +-----------------+-----------------+-----------------+
+| of 2.6.12 |      8 bpp      |     16 bpp      |     32 bpp      |
+|           | noypan |   ypan | noypan |   ypan | noypan |   ypan |
++-----------+--------+--------+--------+--------+--------+--------+
+|    Test 1 |   4.26 |   3.76 |   5.99 |   7.23 |  ----  |  ----  |
+|    Test 2 |  65.65 |   4.89 | 120.88 |   9.08 |  ----  |  ----  |
+|    Test 3 | 126.91 |   5.94 | 235.77 |  11.03 |  ----  |  ----  |
++-----------+--------+--------+--------+--------+--------+--------+
+|  Comments | vga=0x307       | vga=0x31a       | vga=0x31b not   |
+|           | fh=80kHz        | fh=80kHz        | supported by    |
+|           | fv=75kHz        | fv=75kHz        | video BIOS and  |
+|           |                 |                 | hardware        |
++-----------+-----------------+-----------------+-----------------+
+
+
++-----------+-----------------------------------------------------+
+|           |                     accelerated                     |
+|  CYBLAFB  +-----------------+-----------------+-----------------+
+|           |      8 bpp      |     16 bpp      |     32 bpp      |
+|           | noypan |   ypan | noypan |   ypan | noypan |   ypan |
++-----------+--------+--------+--------+--------+--------+--------+
+|    Test 1 |   8.02 |   0.23 |  19.04 |   0.61 |  57.12 |   2.74 |
+|    Test 2 |   8.38 |   0.55 |  19.39 |   0.92 |  57.54 |   3.13 |
+|    Test 3 |   8.73 |   0.86 |  19.74 |   1.24 |  57.95 |   3.51 |
++-----------+--------+--------+--------+--------+--------+--------+
+|  Comments |                 |                 |                 |
+|           |                 |                 |                 |
+|           |                 |                 |                 |
+|           |                 |                 |                 |
++-----------+-----------------+-----------------+-----------------+
+
diff --git a/Documentation/fb/cyblafb/todo b/Documentation/fb/cyblafb/todo
new file mode 100644
index 000000000000..80fb2f89b6c1
--- /dev/null
+++ b/Documentation/fb/cyblafb/todo
@@ -0,0 +1,32 @@
+TODO / Missing features
+=======================
+
+Verify LCD stuff                "stretch" and "center" options are
+                                completely untested ... this code needs to be
+                                verified. As I don't have access to such
+                                hardware, please contact me if you are
+                                willing run some tests.
+
+Interlaced video modes          The reason that interleaved
+                                modes are disabled is that I do not know
+                                the meaning of the vertical interlace
+                                parameter. Also the datasheet mentions a
+                                bit d8 of a horizontal interlace parameter,
+                                but nowhere the lower 8 bits. Please help
+                                if you can.
+
+low-res double scan modes       Who needs it?
+
+accelerated color blitting      Who needs it? The console driver does use color
+                                blitting for nothing but drawing the penguine,
+                                everything else is done using color expanding
+                                blitting of 1bpp character bitmaps.
+
+xpanning                        Who needs it?
+
+ioctls                          Who needs it?
+
+TV-out                          Will be done later
+
+???                             Feel free to contact me if you have any
+                                feature requests
diff --git a/Documentation/fb/cyblafb/usage b/Documentation/fb/cyblafb/usage
new file mode 100644
index 000000000000..e627c8f54211
--- /dev/null
+++ b/Documentation/fb/cyblafb/usage
@@ -0,0 +1,206 @@
+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.
+
+        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 xres to differ from xres_virtual
+                - 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.
+
+        Any request that violates the rules given above will be ignored and
+        fbset will return an error.
+
+        If you program a virtual y resolution higher than the hardware limit,
+        cyblafb will silently decrease that value to the highest possible
+        value.
+
+        Attempts to disable acceleration are ignored.
+
+        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!
+
+vesafb          allows cyblafb to be loaded after vesafb has been
+                loaded. See sections "Module unloading ...".
+
+
+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 vesafb=1
+        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
+
diff --git a/Documentation/fb/cyblafb/whycyblafb b/Documentation/fb/cyblafb/whycyblafb
new file mode 100644
index 000000000000..a123bc11e698
--- /dev/null
+++ b/Documentation/fb/cyblafb/whycyblafb
@@ -0,0 +1,85 @@
+I tried the following framebuffer drivers:
+
+        - TRIDENTFB is full of bugs. Acceleration is broken for Blade3D
+          graphics cores like the cyberblade/i1. It claims to support a great
+          number of devices, but documentation for most of these devices is
+          unfortunately not available. There is _no_ reason to use tridentfb
+          for cyberblade/i1 + CRT users. VESAFB is faster, and the one
+          advantage, mode switching, is broken in tridentfb.
+
+        - VESAFB is used by many distributions as a standard. Vesafb does
+          not support mode switching. VESAFB is a bit faster than the working
+          configurations of TRIDENTFB, but it is still too slow, even if you
+          use ypan.
+
+        - EPIAFB (you'll find it on sourceforge) supports the Cyberblade/i1
+          graphics core, but it still has serious bugs and developement seems
+          to have stopped. This is the one driver with TV-out support. If you
+          do need this feature, try epiafb.
+
+None of these drivers was a real option for me.
+
+I believe that is unreasonable to change code that announces to support 20
+devices if I only have more or less sufficient documentation for exactly one
+of these. The risk of breaking device foo while fixing device bar is too high.
+
+So I decided to start CyBlaFB as a stripped down tridentfb.
+
+All code specific to other Trident chips has been removed. After that there
+were a lot of cosmetic changes to increase the readability of the code. All
+register names were changed to those mnemonics used in the datasheet. Function
+and macro names were changed if they hindered easy understanding of the code.
+
+After that I debugged the code and implemented some new features. I'll try to
+give a little summary of the main changes:
+
+        - calculation of vertical and horizontal timings was fixed
+
+        - video signal quality has been improved dramatically
+
+        - acceleration:
+
+                - fillrect and copyarea were fixed and reenabled
+
+                - color expanding imageblit was newly implemented, color
+                  imageblit (only used to draw the penguine) still uses the
+                  generic code.
+
+                - init of the acceleration engine was improved and moved to a
+                  place where it really works ...
+
+                - sync function has a timeout now and tries to reset and
+                  reinit the accel engine if necessary
+
+                - fewer slow copyarea calls when doing ypan scrolling by using
+                  undocumented bit d21 of screen start address stored in
+                  CR2B[5]. BIOS does use it also, so this should be safe.
+
+        - cyblafb rejects any attempt to set modes that would cause vclk
+          values above reasonable 230 MHz. 32bit modes use a clock
+          multiplicator of 2, so fbset does show the correct values for
+          pixclock but not for vclk in this case. The fbset limit is 115 MHz
+          for 32 bpp modes.
+
+        - cyblafb rejects modes known to be broken or unimplemented (all
+          interlaced modes, all doublescan modes for now)
+
+        - cyblafb now works independant of the video mode in effect at startup
+          time (tridentfb does not init all needed registers to reasonable
+          values)
+
+        - switching between video modes does work reliably now
+
+        - the first video mode now is the one selected on startup using the
+          vga=???? mechanism or any of
+                - 640x480, 800x600, 1024x768, 1280x1024
+                - 8, 16, 24 or 32 bpp
+                - refresh between 50 Hz and 85 Hz, 1 Hz steps (1280x1024-32
+                  is limited to 63Hz)
+
+        - pci retry and pci burst mode are settable (try to disable if you
+          experience latency problems)
+
+        - built as a module cyblafb might be unloaded and reloaded using
+          the vfb module and con2vt or might be used together with vesafb
+