linux-kernel - [PATCH 5.16 0152/1017] video: fbdev: atari: Atari 2 bpp (STe) palette bugfix

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Message-Id: <20220405070358.721540908@linuxfoundation.org>
Date:   Tue,  5 Apr 2022 09:17:45 +0200
From:   Greg Kroah-Hartman <gregkh@...uxfoundation.org>
To:     linux-kernel@...r.kernel.org
Cc:     Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        stable@...r.kernel.org, Geert Uytterhoeven <geert@...ux-m68k.org>,
        Michael Schmitz <schmitzmic@...il.com>,
        Helge Deller <deller@....de>
Subject: [PATCH 5.16 0152/1017] video: fbdev: atari: Atari 2 bpp (STe) palette bugfix

From: Michael Schmitz <schmitzmic@...il.com>

commit c8be5edbd36ceed2ff3d6b8f8e40643c3f396ea3 upstream.

The code to set the shifter STe palette registers has a long
standing operator precedence bug, manifesting as colors set
on a 2 bits per pixel frame buffer coming up with a distinctive
blue tint.

Add parentheses around the calculation of the per-color palette
data before shifting those into their respective bit field position.

This bug goes back a long way (2.4 days at the very least) so there
won't be a Fixes: tag.

Tested on ARAnyM as well on Falcon030 hardware.

Cc: stable@...r.kernel.org
Reported-by: Geert Uytterhoeven <geert@...ux-m68k.org>
Link: https://lore.kernel.org/all/CAMuHMdU3ievhXxKR_xi_v3aumnYW7UNUO6qMdhgfyWTyVSsCkQ@mail.gmail.com
Tested-by: Michael Schmitz <schmitzmic@...il.com>
Tested-by: Geert Uytterhoeven <geert@...ux-m68k.org>
Signed-off-by: Michael Schmitz <schmitzmic@...il.com>
Signed-off-by: Helge Deller <deller@....de>
Signed-off-by: Greg Kroah-Hartman <gregkh@...uxfoundation.org>
---
 drivers/video/fbdev/atafb.c |   12 ++++++------
 1 file changed, 6 insertions(+), 6 deletions(-)

--- a/drivers/video/fbdev/atafb.c
+++ b/drivers/video/fbdev/atafb.c
@@ -1683,9 +1683,9 @@ static int falcon_setcolreg(unsigned int
 			   ((blue & 0xfc00) >> 8));
 	if (regno < 16) {
 		shifter_tt.color_reg[regno] =
-			(((red & 0xe000) >> 13) | ((red & 0x1000) >> 12) << 8) |
-			(((green & 0xe000) >> 13) | ((green & 0x1000) >> 12) << 4) |
-			((blue & 0xe000) >> 13) | ((blue & 0x1000) >> 12);
+			((((red & 0xe000) >> 13)   | ((red & 0x1000) >> 12)) << 8)   |
+			((((green & 0xe000) >> 13) | ((green & 0x1000) >> 12)) << 4) |
+			   ((blue & 0xe000) >> 13) | ((blue & 0x1000) >> 12);
 		((u32 *)info->pseudo_palette)[regno] = ((red & 0xf800) |
 						       ((green & 0xfc00) >> 5) |
 						       ((blue & 0xf800) >> 11));
@@ -1971,9 +1971,9 @@ static int stste_setcolreg(unsigned int
 	green >>= 12;
 	if (ATARIHW_PRESENT(EXTD_SHIFTER))
 		shifter_tt.color_reg[regno] =
-			(((red & 0xe) >> 1) | ((red & 1) << 3) << 8) |
-			(((green & 0xe) >> 1) | ((green & 1) << 3) << 4) |
-			((blue & 0xe) >> 1) | ((blue & 1) << 3);
+			((((red & 0xe)   >> 1) | ((red & 1)   << 3)) << 8) |
+			((((green & 0xe) >> 1) | ((green & 1) << 3)) << 4) |
+			  ((blue & 0xe)  >> 1) | ((blue & 1)  << 3);
 	else
 		shifter_tt.color_reg[regno] =
 			((red & 0xe) << 7) |