Fix off-by-one error in xf86SetWeight(); ffs(3) returns one-based index,
but most drivers expect zero-based one. Few drivers work around this bug
by themselves. So, remove these codes simultanemously.

Index: xsrc/external/mit/xf86-video-geode/dist/src/gx_video.c
===================================================================
RCS file: /home/netbsd/xsrc/external/mit/xf86-video-geode/dist/src/gx_video.c,v
retrieving revision 1.2
diff -p -u -r1.2 gx_video.c
--- xsrc/external/mit/xf86-video-geode/dist/src/gx_video.c	30 May 2017 15:54:38 -0000	1.2
+++ xsrc/external/mit/xf86-video-geode/dist/src/gx_video.c	28 May 2021 09:21:47 -0000
@@ -300,7 +300,7 @@ GXSetColorkey(ScrnInfoPtr pScrni, GeodeP
         green = ((key >> 8) & 0xFF);
         blue = (key & 0xFF);
         break;
-    case 16:
+    default:
         red = (pPriv->colorKey & pScrni->mask.red) >>
             pScrni->offset.red << (8 - pScrni->weight.red);
         green = (pPriv->colorKey & pScrni->mask.green) >>
@@ -308,18 +308,6 @@ GXSetColorkey(ScrnInfoPtr pScrni, GeodeP
         blue = (pPriv->colorKey & pScrni->mask.blue) >>
             pScrni->offset.blue << (8 - pScrni->weight.blue);
         break;
-    default:
-        /* for > 16 bpp we send in the mask in xf86SetWeight. This
-         * function is providing the offset by 1 more. So we take
-         * this as a special case and subtract 1 for > 16
-         */
-        red = (pPriv->colorKey & pScrni->mask.red) >>
-            (pScrni->offset.red - 1) << (8 - pScrni->weight.red);
-        green = (pPriv->colorKey & pScrni->mask.green) >>
-            (pScrni->offset.green - 1) << (8 - pScrni->weight.green);
-        blue = (pPriv->colorKey & pScrni->mask.blue) >>
-            (pScrni->offset.blue - 1) << (8 - pScrni->weight.blue);
-        break;
     }
 
     GFX(set_video_color_key((blue | (green << 8) | (red << 16)), 0xFFFFFF,
Index: xsrc/external/mit/xf86-video-geode/dist/src/lx_video.c
===================================================================
RCS file: /home/netbsd/xsrc/external/mit/xf86-video-geode/dist/src/lx_video.c,v
retrieving revision 1.2
diff -p -u -r1.2 lx_video.c
--- xsrc/external/mit/xf86-video-geode/dist/src/lx_video.c	30 May 2017 15:54:38 -0000	1.2
+++ xsrc/external/mit/xf86-video-geode/dist/src/lx_video.c	28 May 2021 09:22:14 -0000
@@ -146,7 +146,7 @@ LXSetColorkey(ScrnInfoPtr pScrni, GeodeP
         green = ((key >> 8) & 0xFF);
         blue = (key & 0xFF);
         break;
-    case 16:
+    default:
         red = (pPriv->colorKey & pScrni->mask.red) >>
             pScrni->offset.red << (8 - pScrni->weight.red);
         green = (pPriv->colorKey & pScrni->mask.green) >>
@@ -154,19 +154,6 @@ LXSetColorkey(ScrnInfoPtr pScrni, GeodeP
         blue = (pPriv->colorKey & pScrni->mask.blue) >>
             pScrni->offset.blue << (8 - pScrni->weight.blue);
         break;
-    default:
-        /* for > 16 bpp we send in the mask in xf86SetWeight. This
-         * function is providing the offset by 1 more. So we take
-         * this as a special case and subtract 1 for > 16
-         */
-
-        red = (pPriv->colorKey & pScrni->mask.red) >>
-            (pScrni->offset.red - 1) << (8 - pScrni->weight.red);
-        green = (pPriv->colorKey & pScrni->mask.green) >>
-            (pScrni->offset.green - 1) << (8 - pScrni->weight.green);
-        blue = (pPriv->colorKey & pScrni->mask.blue) >>
-            (pScrni->offset.blue - 1) << (8 - pScrni->weight.blue);
-        break;
     }
 
     df_set_video_color_key((blue | (green << 8) | (red << 16)),
Index: xsrc/external/mit/xf86-video-nouveau/dist/src/nv_driver.c
===================================================================
RCS file: /home/netbsd/xsrc/external/mit/xf86-video-nouveau/dist/src/nv_driver.c,v
retrieving revision 1.4
diff -p -u -r1.4 nv_driver.c
--- xsrc/external/mit/xf86-video-nouveau/dist/src/nv_driver.c	27 Apr 2021 01:22:55 -0000	1.4
+++ xsrc/external/mit/xf86-video-nouveau/dist/src/nv_driver.c	28 May 2021 09:23:39 -0000
@@ -1002,11 +1002,6 @@ NVPreInit(ScrnInfoPtr pScrn, int flags)
 		rgbmask.blue  = 0x3ff00000;
 		if (!xf86SetWeight(pScrn, rgbzeros, rgbmask))
 			NVPreInitFail("\n");
-
-		/* xf86SetWeight() seems to think ffs(1) == 0... */
-		pScrn->offset.red--;
-		pScrn->offset.green--;
-		pScrn->offset.blue--;
 	} else {
 		if (!xf86SetWeight(pScrn, rgbzeros, rgbzeros))
 			NVPreInitFail("\n");
Index: xsrc/external/mit/xf86-video-nsc/dist/src/nsc_gx2_video.c
===================================================================
RCS file: /home/netbsd/xsrc/external/mit/xf86-video-nsc/dist/src/nsc_gx2_video.c,v
retrieving revision 1.1.1.1
diff -p -u -r1.1.1.1 nsc_gx2_video.c
--- xsrc/external/mit/xf86-video-nsc/dist/src/nsc_gx2_video.c	2 Aug 2008 05:13:44 -0000	1.1.1.1
+++ xsrc/external/mit/xf86-video-nsc/dist/src/nsc_gx2_video.c	28 May 2021 09:23:59 -0000
@@ -368,7 +368,7 @@ GX2SetColorkey(ScrnInfoPtr pScrn, GeodeP
       green = ((key >> 8) & 0xFF);
       blue = (key & 0xFF);
       break;
-   case 16:
+   default:
       red = (pPriv->colorKey & pScrn->mask.red) >>
 	    pScrn->offset.red << (8 - pScrn->weight.red);
       green = (pPriv->colorKey & pScrn->mask.green) >>
@@ -376,18 +376,6 @@ GX2SetColorkey(ScrnInfoPtr pScrn, GeodeP
       blue = (pPriv->colorKey & pScrn->mask.blue) >>
 	    pScrn->offset.blue << (8 - pScrn->weight.blue);
       break;
-   default:
-      /* for > 16 bpp we send in the mask in xf86SetWeight. This
-       * function is providing the offset by 1 more. So we take 
-       * this as a special case and subtract 1 for > 16
-       */
-      red = (pPriv->colorKey & pScrn->mask.red) >>
-	    (pScrn->offset.red - 1) << (8 - pScrn->weight.red);
-      green = (pPriv->colorKey & pScrn->mask.green) >>
-	    (pScrn->offset.green - 1) << (8 - pScrn->weight.green);
-      blue = (pPriv->colorKey & pScrn->mask.blue) >>
-	    (pScrn->offset.blue - 1) << (8 - pScrn->weight.blue);
-      break;
    }
 
    GFX(set_video_color_key((blue | (green << 8) | (red << 16)), 0xFFFFFF,
Index: xsrc/external/mit/xorg-server/dist/hw/xfree86/common/xf86Helper.c
===================================================================
RCS file: /home/netbsd/xsrc/external/mit/xorg-server/dist/hw/xfree86/common/xf86Helper.c,v
retrieving revision 1.4
diff -p -u -r1.4 xf86Helper.c
--- xsrc/external/mit/xorg-server/dist/hw/xfree86/common/xf86Helper.c	31 Dec 2018 09:50:00 -0000	1.4
+++ xsrc/external/mit/xorg-server/dist/hw/xfree86/common/xf86Helper.c	28 May 2021 09:25:18 -0000
@@ -728,9 +728,9 @@ xf86SetWeight(ScrnInfoPtr scrp, rgb weig
         scrp->mask.red = mask.red;
         scrp->mask.green = mask.green;
         scrp->mask.blue = mask.blue;
-        scrp->offset.red = ffs(mask.red);
-        scrp->offset.green = ffs(mask.green);
-        scrp->offset.blue = ffs(mask.blue);
+        scrp->offset.red = ffs(mask.red) - 1;
+        scrp->offset.green = ffs(mask.green) - 1;
+        scrp->offset.blue = ffs(mask.blue) - 1;
     }
     return TRUE;
 }
Index: xsrc/external/mit/xorg-server.old/dist/hw/xfree86/common/xf86Helper.c
===================================================================
RCS file: /home/netbsd/xsrc/external/mit/xorg-server.old/dist/hw/xfree86/common/xf86Helper.c,v
retrieving revision 1.1.1.1
diff -p -u -r1.1.1.1 xf86Helper.c
--- xsrc/external/mit/xorg-server.old/dist/hw/xfree86/common/xf86Helper.c	9 Jun 2016 09:07:58 -0000	1.1.1.1
+++ xsrc/external/mit/xorg-server.old/dist/hw/xfree86/common/xf86Helper.c	28 May 2021 09:25:44 -0000
@@ -760,9 +760,9 @@ xf86SetWeight(ScrnInfoPtr scrp, rgb weig
 	scrp->mask.red = mask.red;
 	scrp->mask.green = mask.green;
 	scrp->mask.blue = mask.blue;
-	scrp->offset.red = ffs(mask.red);
-	scrp->offset.green = ffs(mask.green);
-	scrp->offset.blue = ffs(mask.blue);
+	scrp->offset.red = ffs(mask.red) - 1;
+	scrp->offset.green = ffs(mask.green) - 1;
+	scrp->offset.blue = ffs(mask.blue) - 1;
     }
     return TRUE;
 }