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Commit ebde4411 authored by Michal Januszewski's avatar Michal Januszewski Committed by Linus Torvalds
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fbdev: fix color component field length documentation 



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: default avatarMichal Januszewski <spock@gentoo.org>
Acked-by: default avatarKrzysztof Helt <krzysztof.h1@poczta.fm>
Cc: <syrjala@sci.fi>
Acked-by: default avatarGeert Uytterhoeven <geert.uytterhoeven@gmail.com>
Signed-off-by: default avatarAndrew Morton <akpm@linux-foundation.org>
Signed-off-by: default avatarLinus Torvalds <torvalds@linux-foundation.org>
parent 513adb58

drivers/video/skeletonfb.c

+5 −3
Original line number Diff line number Diff line
@@ -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

drivers/video/vfb.c

+7 −4
Original line number Diff line number Diff line
@@ -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

include/linux/fb.h

+6 −2
Original line number Diff line number Diff line
@@ -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	*/