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fbdev: fix color component field length documentation

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The documentation about the meaning of the color component bitfield
lengths in pseudocolor modes is inconsistent.  Fix it, so that it
indicates the correct interpretation everywhere, i.e.  that 1 << length is
the number of palette entries.

Signed-off-by: Michal Januszewski <spock@gentoo.org>
Acked-by: Krzysztof Helt <krzysztof.h1@poczta.fm>
Cc: <syrjala@sci.fi>
Acked-by: Geert Uytterhoeven <geert.uytterhoeven@gmail.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
This commit is contained in:
Michal Januszewski 2009-04-13 14:39:41 -07:00 committed by Linus Torvalds
parent 513adb5868
commit ebde441177
3 changed files with 18 additions and 9 deletions
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8
drivers/video/skeletonfb.c
View File

@ -308,9 +308,11 @@ static int xxxfb_setcolreg(unsigned regno, unsigned red, unsigned green,
* color depth = SUM(var->{color}.length)
*
* Pseudocolor:
* var->{color}.offset is 0
* var->{color}.length contains width of DAC or the number of unique
* colors available (color depth)
* var->{color}.offset is 0 unless the palette index takes less than
* bits_per_pixel bits and is stored in the upper
* bits of the pixel value
* var->{color}.length is set so that 1 << length is the number of
* available palette entries
* pseudo_palette is not used
* RAMDAC[X] is programmed to (red, green, blue)
* color depth = var->{color}.length

9
drivers/video/vfb.c
View File

@ -320,11 +320,14 @@ static int vfb_setcolreg(u_int regno, u_int red, u_int green, u_int blue,
* RAMDAC[X] is programmed to (red, green, blue)
*
* Pseudocolor:
* uses offset = 0 && length = RAMDAC register width.
* var->{color}.offset is 0
* var->{color}.length contains widht of DAC
* var->{color}.offset is 0 unless the palette index takes less than
* bits_per_pixel bits and is stored in the upper
* bits of the pixel value
* var->{color}.length is set so that 1 << length is the number of available
* palette entries
* cmap is not used
* RAMDAC[X] is programmed to (red, green, blue)
*
* Truecolor:
* does not use DAC. Usually 3 are present.
* var->{color}.offset contains start of bitfield

8
include/linux/fb.h
View File

@ -173,8 +173,12 @@ struct fb_fix_screeninfo {
/* Interpretation of offset for color fields: All offsets are from the right,
* inside a "pixel" value, which is exactly 'bits_per_pixel' wide (means: you
* can use the offset as right argument to <<). A pixel afterwards is a bit
* stream and is written to video memory as that unmodified. This implies
* big-endian byte order if bits_per_pixel is greater than 8.
* stream and is written to video memory as that unmodified.
*
* For pseudocolor: offset and length should be the same for all color
* components. Offset specifies the position of the least significant bit
* of the pallette index in a pixel value. Length indicates the number
* of available palette entries (i.e. # of entries = 1 << length).
*/
struct fb_bitfield {
__u32 offset; /* beginning of bitfield */