fbsplash: support 8bit mode

Fake truecolor support using a RGB:332 palette.

function                                             old     new   delta
fb_setpal                                              -     172    +172
fbsplash_main                                        920     953     +33
fb_pixel_value                                        50      80     +30
fb_write_pixel                                        47      51      +4
------------------------------------------------------------------------------
(add/remove: 1/0 grow/shrink: 3/0 up/down: 239/0)             Total: 239 bytes

Signed-off-by: Peter Korsgaard <jacmet@sunsite.dk>
Signed-off-by: Denys Vlasenko <vda.linux@googlemail.com>

1 files changed, 64 insertions, 5 deletions

diff --git a/miscutils/fbsplash.c b/miscutils/fbsplash.c
index bc9ac8fe1..04d583df6 100644
--- a/miscutils/fbsplash.c
+++ b/miscutils/fbsplash.c
@@ -74,6 +74,43 @@ struct globals {
 #define DEBUG_MESSAGE(...) ((void)0)
 #endif
 
+/**
+ * Configure palette for RGB:332
+ */
+static void fb_setpal(int fd)
+{
+        struct fb_cmap cmap;
+        /* fb colors are 16 bit */
+        unsigned short red[256], green[256], blue[256];
+        unsigned i;
+
+        /* RGB:332 */
+        for (i = 0; i < 256; i++) {
+                /* Color is encoded in pixel value as rrrgggbb.
+                 * 3-bit color is mapped to 16-bit one as:
+                 * 000 -> 00000000 00000000
+                 * 001 -> 00100100 10010010
+                 * ...
+                 * 011 -> 01101101 10110110
+                 * 100 -> 10010010 01001001
+                 * ...
+                 * 111 -> 11111111 11111111
+                 */
+                red[i]   = (( i >> 5       ) * 0x9249) >> 2; // rrr * 00 10010010 01001001 >> 2
+                green[i] = (((i >> 2) & 0x7) * 0x9249) >> 2; // ggg * 00 10010010 01001001 >> 2
+                /* 2-bit color is easier: */
+                blue[i]  =  ( i       & 0x3) * 0x5555; // bb * 01010101 01010101
+        }
+
+        cmap.start = 0;
+        cmap.len   = 256;
+        cmap.red   = red;
+        cmap.green = green;
+        cmap.blue  = blue;
+        cmap.transp = 0;
+
+        xioctl(fd, FBIOPUTCMAP, &cmap);
+}
 
 /**
  * Open and initialize the framebuffer device
@@ -87,8 +124,21 @@ static void fb_open(const char *strfb_device)
         xioctl(fbfd, FBIOGET_VSCREENINFO, &G.scr_var);
         xioctl(fbfd, FBIOGET_FSCREENINFO, &G.scr_fix);
 
-        if (G.scr_var.bits_per_pixel < 16 || G.scr_var.bits_per_pixel > 32)
+        switch (G.scr_var.bits_per_pixel) {
+        case 8:
+                fb_setpal(fbfd);
+                break;
+
+        case 16:
+        case 24:
+        case 32:
+                break;
+
+        default:
                 bb_error_msg_and_die("unsupported %u bpp", (int)G.scr_var.bits_per_pixel);
+                break;
+        }
+
         G.bytes_per_pixel = (G.scr_var.bits_per_pixel + 7) >> 3;
 
         // map the device in memory
@@ -109,11 +159,17 @@ static void fb_open(const char *strfb_device)
  */
 static unsigned fb_pixel_value(unsigned r, unsigned g, unsigned b)
 {
+        if (G.bytes_per_pixel == 1) {
+                r = r        & 0xe0; // 3-bit red
+                g = (g >> 3) & 0x1c; // 3-bit green
+                b =  b >> 6;         // 2-bit blue
+                return r + g + b;
+        }
         if (G.bytes_per_pixel == 2) {
-                r >>= 3;  // 5-bit red
-                g >>= 2;  // 6-bit green
-                b >>= 3;  // 5-bit blue
-                return b + (g << 5) + (r << (5+6));
+                r = (r & 0xf8) << 8; // 5-bit red
+                g = (g & 0xfc) << 3; // 6-bit green
+                b =  b >> 3;         // 5-bit blue
+                return r + g + b;
         }
         // RGB 888
         return b + (g << 8) + (r << 16);
@@ -125,6 +181,9 @@ static unsigned fb_pixel_value(unsigned r, unsigned g, unsigned b)
 static void fb_write_pixel(unsigned char *addr, unsigned pixel)
 {
         switch (G.bytes_per_pixel) {
+        case 1:
+                *addr = pixel;
+                break;
         case 2:
                 *(uint16_t *)addr = pixel;
                 break;