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>

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;
 		}
 	}

drivers/video/fb_draw.h

@@ -33,11 +33,11 @@ pixel_to_pat( u32 bpp, u32 pixel)
 	case 8:
 		return 0x0101010101010101ul*pixel;
 	case 12:
-		return 0x0001001001001001ul*pixel;
+		return 0x1001001001001001ul*pixel;
 	case 16:
 		return 0x0001000100010001ul*pixel;
 	case 24:
-		return 0x0000000001000001ul*pixel;
+		return 0x0001000001000001ul*pixel;
 	case 32:
 		return 0x0000000100000001ul*pixel;
 	default:
@@ -58,11 +58,11 @@ pixel_to_pat( u32 bpp, u32 pixel)
 	case 8:
 		return 0x01010101ul*pixel;
 	case 12:
-		return 0x00001001ul*pixel;
+		return 0x01001001ul*pixel;
 	case 16:
 		return 0x00010001ul*pixel;
 	case 24:
-		return 0x00000001ul*pixel;
+		return 0x01000001ul*pixel;
 	case 32:
 		return 0x00000001ul*pixel;
 	default:
@@ -167,4 +167,17 @@ static inline unsigned long fb_rev_pixels_in_long(unsigned long val,
 
 #endif  /* CONFIG_FB_CFB_REV_PIXELS_IN_BYTE */
 
+#define cpu_to_le_long _cpu_to_le_long(BITS_PER_LONG)
+#define _cpu_to_le_long(x) __cpu_to_le_long(x)
+#define __cpu_to_le_long(x) cpu_to_le##x
+
+#define le_long_to_cpu _le_long_to_cpu(BITS_PER_LONG)
+#define _le_long_to_cpu(x) __le_long_to_cpu(x)
+#define __le_long_to_cpu(x) le##x##_to_cpu
+
+static inline unsigned long rolx(unsigned long word, unsigned int shift, unsigned int x)
+{
+	return (word << shift) | (word >> (x - shift));
+}
+
 #endif /* FB_DRAW_H */

drivers/video/sysfillrect.c

@@ -124,7 +124,7 @@ bitfill_unaligned(struct fb_info *p, unsigned long *dst, int dst_idx,
 
 		/* Trailing bits */
 		if (last)
-			*dst = comp(pat, *dst, first);
+			*dst = comp(pat, *dst, last);
 	}
 }
 
@@ -242,7 +242,7 @@ bitfill_unaligned_rev(struct fb_info *p, unsigned long *dst, int dst_idx,
 
 void sys_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;
@@ -292,17 +292,16 @@ void sys_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 *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;
@@ -311,18 +310,19 @@ void sys_fillrect(struct fb_info *p, const struct fb_fillrect *rect)
 			fill_op = bitfill_unaligned;
 			break;
 		default:
-			printk(KERN_ERR "cfb_fillrect(): unknown rop, "
+			printk(KERN_ERR "sys_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;
 		}
 	}