[PATCH] fbcon: Saner 16-color to 4-color conversion

Currently, the default linux 16-colors are converted to 4-colors by simply
dividing the values by 4.  However, this is not necessarily correct since the
first 4 colors are converted to black, rendering them invisible.

So, for black, no conversion; for light colors, convert to gray, for normal
text color, no conversion, and for bright colors, convert to intense white.

Signed-off-by: Antonino Daplas <adaplas@pol.net>
Signed-off-by: Andrew Morton <akpm@osdl.org>
Signed-off-by: Linus Torvalds <torvalds@osdl.org>

1 files changed, 19 insertions, 2 deletions

diff --git a/drivers/video/console/fbcon.c b/drivers/video/console/fbcon.c
index 88bd8ef56fde..bb4ea50b54a3 100644
--- a/drivers/video/console/fbcon.c
+++ b/drivers/video/console/fbcon.c
@@ -247,9 +247,26 @@ static inline int get_color(struct vc_data *vc, struct fb_info *info,
         case 2:
                 /*
                  * Scale down 16-colors to 4 colors. Default 4-color palette
-                 * is grayscale.
+                 * is grayscale. However, simply dividing the values by 4
+                 * will not work, as colors 1, 2 and 3 will be scaled-down
+                 * to zero rendering them invisible.  So empirically convert
+                 * colors to a sane 4-level grayscale.
                  */
-                color /= 4;
+                switch (color) {
+                case 0:
+                        color = 0; /* black */
+                        break;
+                case 1 ... 6:
+                        color = 2; /* white */
+                        break;
+                case 7 ... 8:
+                        color = 1; /* gray */
+                        break;
+                default:
+                        color = 3; /* intense white */
+                        break;
+                }
+                break;
         case 3:
                 /*
                  * Last 8 entries of default 16-color palette is a more intense