fbdev: fix fillrect for 24bpp modes

The software fillrect routines do not work properly when the number of
pixels per machine word is not an integer.  To see that, run the following
command on a fbdev console with a 24bpp video mode, using a
non-accelerated driver such as (u)vesafb:

  reset ; echo -e '\e[41mtest\e[K'

The expected result is 'test' displayed on a line with red background.
Instead of that, 'test' has a red background, but the rest of the line
(rendered using fillrect()) contains a distored colorful pattern.

This patch fixes the problem by correctly computing rotation shifts.  It
has been tested in a 24bpp mode on 32- and 64-bit little-endian machines.

Signed-off-by: Michal Januszewski <spock@gentoo.org>
Acked-by: Krzysztof Helt <krzysztof.h1@wp.pl>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

1 files changed, 16 insertions, 20 deletions

diff --git a/drivers/video/cfbfillrect.c b/drivers/video/cfbfillrect.c
index 64b3576..ba9f58b 100644
--- a/drivers/video/cfbfillrect.c
+++ b/drivers/video/cfbfillrect.c
@@ -9,10 +9,6 @@
  *
  * NOTES:
  *
- *  The code for depths like 24 that don't have integer number of pixels per
- *  long is broken and needs to be fixed. For now I turned these types of
- *  mode off.
- *
  *  Also need to add code to deal with cards endians that are different than
  *  the native cpu endians. I also need to deal with MSB position in the word.
  *
@@ -139,7 +135,7 @@ bitfill_unaligned(struct fb_info *p, unsigned long __iomem *dst, int dst_idx,
 
 		// Trailing bits
 		if (last)
-			FB_WRITEL(comp(pat, FB_READL(dst), first), dst);
+			FB_WRITEL(comp(pat, FB_READL(dst), last), dst);
 	}
 }
 
@@ -281,7 +277,7 @@ bitfill_unaligned_rev(struct fb_info *p, unsigned long __iomem *dst,
 
 void cfb_fillrect(struct fb_info *p, const struct fb_fillrect *rect)
 {
-	unsigned long pat, fg;
+	unsigned long pat, pat2, fg;
 	unsigned long width = rect->width, height = rect->height;
 	int bits = BITS_PER_LONG, bytes = bits >> 3;
 	u32 bpp = p->var.bits_per_pixel;
@@ -297,7 +293,7 @@ void cfb_fillrect(struct fb_info *p, const struct fb_fillrect *rect)
 	else
 		fg = rect->color;
 
-	pat = pixel_to_pat( bpp, fg);
+	pat = pixel_to_pat(bpp, fg);
 
 	dst = (unsigned long __iomem *)((unsigned long)p->screen_base & ~(bytes-1));
 	dst_idx = ((unsigned long)p->screen_base & (bytes - 1))*8;
@@ -333,17 +329,16 @@ void cfb_fillrect(struct fb_info *p, const struct fb_fillrect *rect)
 			dst_idx += p->fix.line_length*8;
 		}
 	} else {
-		int right;
-		int r;
-		int rot = (left-dst_idx) % bpp;
+		int right, r;
 		void (*fill_op)(struct fb_info *p, unsigned long __iomem *dst,
 				int dst_idx, unsigned long pat, int left,
 				int right, unsigned n, int bits) = NULL;
-
-		/* rotate pattern to correct start position */
-		pat = pat << rot | pat >> (bpp-rot);
-
-		right = bpp-left;
+#ifdef __LITTLE_ENDIAN
+		right = left;
+		left = bpp - right;
+#else
+		right = bpp - left;
+#endif
 		switch (rect->rop) {
 		case ROP_XOR:
 			fill_op = bitfill_unaligned_rev;
@@ -352,17 +347,18 @@ void cfb_fillrect(struct fb_info *p, const struct fb_fillrect *rect)
 			fill_op = bitfill_unaligned;
 			break;
 		default:
-			printk( KERN_ERR "cfb_fillrect(): unknown rop, defaulting to ROP_COPY\n");
+			printk(KERN_ERR "cfb_fillrect(): unknown rop, defaulting to ROP_COPY\n");
 			fill_op = bitfill_unaligned;
 			break;
 		}
 		while (height--) {
-			dst += dst_idx >> (ffs(bits) - 1);
+			dst += dst_idx / bits;
 			dst_idx &= (bits - 1);
-			fill_op(p, dst, dst_idx, pat, left, right,
+			r = dst_idx % bpp;
+			/* rotate pattern to the correct start position */
+			pat2 = le_long_to_cpu(rolx(cpu_to_le_long(pat), r, bpp));
+			fill_op(p, dst, dst_idx, pat2, left, right,
 				width*bpp, bits);
-			r = (p->fix.line_length*8) % bpp;
-			pat = pat << (bpp-r) | pat >> r;
 			dst_idx += p->fix.line_length*8;
 		}
 	}