diff options
Diffstat (limited to 'Documentation/fb')
| -rw-r--r-- | Documentation/fb/cmap_xfbdev.txt | 53 | ||||
| -rw-r--r-- | Documentation/fb/metronomefb.txt | 38 |
2 files changed, 91 insertions, 0 deletions
diff --git a/Documentation/fb/cmap_xfbdev.txt b/Documentation/fb/cmap_xfbdev.txt new file mode 100644 index 0000000..55e1f0a --- /dev/null +++ b/Documentation/fb/cmap_xfbdev.txt @@ -0,0 +1,53 @@ +Understanding fbdev's cmap +-------------------------- + +These notes explain how X's dix layer uses fbdev's cmap structures. + +*. example of relevant structures in fbdev as used for a 3-bit grayscale cmap +struct fb_var_screeninfo { + .bits_per_pixel = 8, + .grayscale = 1, + .red = { 4, 3, 0 }, + .green = { 0, 0, 0 }, + .blue = { 0, 0, 0 }, +} +struct fb_fix_screeninfo { + .visual = FB_VISUAL_STATIC_PSEUDOCOLOR, +} +for (i = 0; i < 8; i++) + info->cmap.red[i] = (((2*i)+1)*(0xFFFF))/16; +memcpy(info->cmap.green, info->cmap.red, sizeof(u16)*8); +memcpy(info->cmap.blue, info->cmap.red, sizeof(u16)*8); + +*. X11 apps do something like the following when trying to use grayscale. +for (i=0; i < 8; i++) { + char colorspec[64]; + memset(colorspec,0,64); + sprintf(colorspec, "rgb:%x/%x/%x", i*36,i*36,i*36); + if (!XParseColor(outputDisplay, testColormap, colorspec, &wantedColor)) + printf("Can't get color %s\n",colorspec); + XAllocColor(outputDisplay, testColormap, &wantedColor); + grays[i] = wantedColor; +} +There's also named equivalents like gray1..x provided you have an rgb.txt. + +Somewhere in X's callchain, this results in a call to X code that handles the +colormap. For example, Xfbdev hits the following: + +xc-011010/programs/Xserver/dix/colormap.c: + +FindBestPixel(pentFirst, size, prgb, channel) + +dr = (long) pent->co.local.red - prgb->red; +dg = (long) pent->co.local.green - prgb->green; +db = (long) pent->co.local.blue - prgb->blue; +sq = dr * dr; +UnsignedToBigNum (sq, &sum); +BigNumAdd (&sum, &temp, &sum); + +co.local.red are entries that were brought in through FBIOGETCMAP which come +directly from the info->cmap.red that was listed above. The prgb is the rgb +that the app wants to match to. The above code is doing what looks like a least +squares matching function. That's why the cmap entries can't be set to the left +hand side boundaries of a color range. + diff --git a/Documentation/fb/metronomefb.txt b/Documentation/fb/metronomefb.txt new file mode 100644 index 0000000..b9a2e7b --- /dev/null +++ b/Documentation/fb/metronomefb.txt @@ -0,0 +1,38 @@ + Metronomefb + ----------- +Maintained by Jaya Kumar <jayakumar.lkml.gmail.com> +Last revised: Nov 20, 2007 + +Metronomefb is a driver for the Metronome display controller. The controller +is from E-Ink Corporation. It is intended to be used to drive the E-Ink +Vizplex display media. E-Ink hosts some details of this controller and the +display media here http://www.e-ink.com/products/matrix/metronome.html . + +Metronome is interfaced to the host CPU through the AMLCD interface. The +host CPU generates the control information and the image in a framebuffer +which is then delivered to the AMLCD interface by a host specific method. +Currently, that's implemented for the PXA's LCDC controller. The display and +error status are each pulled through individual GPIOs. + +Metronomefb was written for the PXA255/gumstix/lyre combination and +therefore currently has board set specific code in it. If other boards based on +other architectures are available, then the host specific code can be separated +and abstracted out. + +Metronomefb requires waveform information which is delivered via the AMLCD +interface to the metronome controller. The waveform information is expected to +be delivered from userspace via the firmware class interface. The waveform file +can be compressed as long as your udev or hotplug script is aware of the need +to uncompress it before delivering it. metronomefb will ask for waveform.wbf +which would typically go into /lib/firmware/waveform.wbf depending on your +udev/hotplug setup. I have only tested with a single waveform file which was +originally labeled 23P01201_60_WT0107_MTC. I do not know what it stands for. +Caution should be exercised when manipulating the waveform as there may be +a possibility that it could have some permanent effects on the display media. +I neither have access to nor know exactly what the waveform does in terms of +the physical media. + +Metronomefb uses the deferred IO interface so that it can provide a memory +mappable frame buffer. It has been tested with tinyx (Xfbdev). It is known +to work at this time with xeyes, xclock, xloadimage, xpdf. + |