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fbdev/efifb: Fix 16 color palette entry calculation 

When using efifb with a 16-bit (5:6:5) visual, fbcon's text is rendered
in the wrong colors - e.g. text gray (#aaaaaa) is rendered as green
(#50bc50) and neighboring pixels have slightly different values
(such as #50bc78).

The reason is that fbcon loads its 16 color palette through
efifb_setcolreg(), which in turn calculates a 32-bit value to write
into memory for each palette index.
Until now, this code could only handle 8-bit visuals and didn't mask
overlapping values when ORing them.

With this patch, fbcon displays the correct colors when a qemu VM is
booted in 16-bit mode (in GRUB: "set gfxpayload=800x600x16").

Fixes: 7c83172b98 ("x86_64 EFI boot support: EFI frame buffer driver")  # v2.6.24+
Signed-off-by: Max Staudt <mstaudt@suse.de>
Acked-By: Peter Jones <pjones@redhat.com>
Cc: stable@vger.kernel.org
Signed-off-by: Tomi Valkeinen <tomi.valkeinen@ti.com>
This commit is contained in:
Max Staudt 2016-06-13 19:15:59 +02:00 committed by Tomi Valkeinen
parent 7166829215
commit d50b3f43db
1 changed files with 3 additions and 3 deletions
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6
drivers/video/fbdev/efifb.c
View File

@ -50,9 +50,9 @@ static int efifb_setcolreg(unsigned regno, unsigned red, unsigned green,
return 1;
if (regno < 16) {
red >>= 8;
green >>= 8;
blue >>= 8;
red >>= 16 - info->var.red.length;
green >>= 16 - info->var.green.length;
blue >>= 16 - info->var.blue.length;
((u32 *)(info->pseudo_palette))[regno] =
(red << info->var.red.offset) |
(green << info->var.green.offset) |