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author | Jaya Kumar <jayakumar.lkml@gmail.com> | 2008-03-19 17:01:10 -0700 |
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committer | Linus Torvalds <torvalds@linux-foundation.org> | 2008-03-19 18:53:37 -0700 |
commit | de7c6d15e354bc94a846f03749819768c331280a (patch) | |
tree | c917a58576c73d8deb218c1e09858ebaba195697 /Documentation/fb/cmap_xfbdev.txt | |
parent | 9fedc9f1b18f6b931c3b695d7280f17fc308309b (diff) | |
download | op-kernel-dev-de7c6d15e354bc94a846f03749819768c331280a.zip op-kernel-dev-de7c6d15e354bc94a846f03749819768c331280a.tar.gz |
fbdev: defio and Metronomefb
Implement support for the E-Ink Metronome controller. It provides an mmapable
interface to the controller using defio support. It was tested with a gumstix
pxa255 with Vizplex media using Xfbdev and various X clients such as xeyes,
xpdf, xloadimage.
This patch also fixes the following bug: Defio would cause a hang on write
access to the framebuffer as the page fault would be called ad-infinitum. It
fixes fb_defio by setting the mapping to be used by page_mkclean.
Signed-off-by: Jaya Kumar <jayakumar.lkml@gmail.com>
Cc: "Antonino A. Daplas" <adaplas@pol.net>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
Diffstat (limited to 'Documentation/fb/cmap_xfbdev.txt')
-rw-r--r-- | Documentation/fb/cmap_xfbdev.txt | 53 |
1 files changed, 53 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. + |