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: 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>

diff --git a/drivers/video/skeletonfb.c b/drivers/video/skeletonfb.c
index a439159204a8490fe79e2e0bebae3f9b47167481..89158bc71da2b3ea982d355c2e6ee0dfeaee7244 100644 (file)
--- a/drivers/video/skeletonfb.c
+++ b/drivers/video/skeletonfb.c
@@ -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

diff --git a/drivers/video/vfb.c b/drivers/video/vfb.c
index cc919ae465711e17cee1648b61bb679576ed3242..050d432c7d952c3160794e30f22ad5f0cb7d4151 100644 (file)
--- a/drivers/video/vfb.c
+++ b/drivers/video/vfb.c
@@ -318,13 +318,16 @@ static int vfb_setcolreg(u_int regno, u_int red, u_int green, u_int blue,
         *   {hardwarespecific} contains width of RAMDAC
         *   cmap[X] is programmed to (X << red.offset) | (X << green.offset) | (X << blue.offset)
         *   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

diff --git a/include/linux/fb.h b/include/linux/fb.h
index f563c50139325b98c11ec5ea492b36d9aa1b7ee3..330c4b1bfcaa58b32907cd9f050c9cc67b097cb0 100644 (file)
--- a/include/linux/fb.h
+++ b/include/linux/fb.h
@@ -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        */