offb: Fix setting of the pseudo-palette for >8bpp

When using a >8bpp framebuffer, offb advertises truecolor, not directcolor,
and doesn't touch the color map even if it has a corresponding access method
for the real hardware.

Thus it needs to set the pseudo-palette with all 3 components of the color,
like other truecolor framebuffers, not with copies of the color index like
a directcolor framebuffer would do.

This went unnoticed for a long time because it's pretty hard to get offb
to kick in with anything but 8bpp (old BootX under MacOS will do that and
qemu does it).

Signed-off-by: Benjamin Herrenschmidt <benh@kernel.crashing.org>
CC: stable@kernel.org

1 files changed, 23 insertions, 27 deletions

diff --git a/drivers/video/offb.c b/drivers/video/offb.c
index da7cf7936b24..0c4f34311eda 100644
--- a/drivers/video/offb.c
+++ b/drivers/video/offb.c
@@ -101,36 +101,32 @@ static int offb_setcolreg(u_int regno, u_int red, u_int green, u_int blue,
                           u_int transp, struct fb_info *info)
 {
         struct offb_par *par = (struct offb_par *) info->par;
-        int i, depth;
-        u32 *pal = info->pseudo_palette;
-
-        depth = info->var.bits_per_pixel;
-        if (depth == 16)
-                depth = (info->var.green.length == 5) ? 15 : 16;
-
-        if (regno > 255 ||
-            (depth == 16 && regno > 63) ||
-            (depth == 15 && regno > 31))
-                return 1;
-
-        if (regno < 16) {
-                switch (depth) {
-                case 15:
-                        pal[regno] = (regno << 10) | (regno << 5) | regno;
-                        break;
-                case 16:
-                        pal[regno] = (regno << 11) | (regno << 5) | regno;
-                        break;
-                case 24:
-                        pal[regno] = (regno << 16) | (regno << 8) | regno;
-                        break;
-                case 32:
-                        i = (regno << 8) | regno;
-                        pal[regno] = (i << 16) | i;
-                        break;
+
+        if (info->fix.visual == FB_VISUAL_TRUECOLOR) {
+                u32 *pal = info->pseudo_palette;
+                u32 cr = red >> (16 - info->var.red.length);
+                u32 cg = green >> (16 - info->var.green.length);
+                u32 cb = blue >> (16 - info->var.blue.length);
+                u32 value;
+
+                if (regno >= 16)
+                        return -EINVAL;
+
+                value = (cr << info->var.red.offset) |
+                        (cg << info->var.green.offset) |
+                        (cb << info->var.blue.offset);
+                if (info->var.transp.length > 0) {
+                        u32 mask = (1 << info->var.transp.length) - 1;
+                        mask <<= info->var.transp.offset;
+                        value |= mask;
                 }
+                pal[regno] = value;
+                return 0;
         }
 
+        if (regno > 255)
+                return -EINVAL;
+
         red >>= 8;
         green >>= 8;
         blue >>= 8;