lib/fonts: Implement glyph rotation

Move the glyph rotation helpers from fbcon to the font library. Wrap them
behind clean interfaces. Also clear the output memory to zero. Previously,
the implementation relied on the caller to do that.

Go through the fbcon code and callers of the glyph-rotation helpers. In
addition to the font rotation, there's also the cursor code, which uses
the rotation helpers.

The font-rotation relied on a single memset to zero for the whole font.
This is now multiple memsets on each glyph. This will be sorted out when
the font library also implements font rotation.

Building glyph rotation in the font library still depends on
CONFIG_FRAMEBUFFER_CONSOLE_ROTATION=y. If we get more users of the code,
we can still add a dedicated Kconfig symbol to the font library.

No changes have been made to the actual implementation of the rotate_*()
and pattern_*() functions. These will be refactored as separate changes.

v2:
- fix typos

Signed-off-by: Thomas Zimmermann <tzimmermann@suse.de>
Signed-off-by: Helge Deller <deller@gmx.de>

lib/fonts/Makefile

@@ -2,6 +2,7 @@
 # Font handling
 
 font-y := fonts.o
+font-$(CONFIG_FRAMEBUFFER_CONSOLE_ROTATION) += font_rotate.o
 
 # Built-in fonts; sorted by Family-Size in ascending order
 font-$(CONFIG_FONT_6x8)       += font_6x8.o

lib/fonts/font_rotate.c

@@ -0,0 +1,150 @@
+// SPDX-License-Identifier: GPL-2.0-only
+/*
+ * Font rotation
+ *
+ *    Copyright (C) 2005 Antonino Daplas <adaplas @pol.net>
+ *
+ * This file is subject to the terms and conditions of the GNU General Public
+ * License.  See the file COPYING in the main directory of this archive for
+ * more details.
+ */
+
+#include <linux/export.h>
+#include <linux/math.h>
+#include <linux/string.h>
+
+#include "font.h"
+
+static inline int pattern_test_bit(u32 x, u32 y, u32 pitch, const char *pat)
+{
+	u32 tmp = (y * pitch) + x, index = tmp / 8,  bit = tmp % 8;
+
+	pat += index;
+	return (*pat) & (0x80 >> bit);
+}
+
+static inline void pattern_set_bit(u32 x, u32 y, u32 pitch, char *pat)
+{
+	u32 tmp = (y * pitch) + x, index = tmp / 8, bit = tmp % 8;
+
+	pat += index;
+
+	(*pat) |= 0x80 >> bit;
+}
+
+static inline void rotate_cw(const char *in, char *out, u32 width, u32 height)
+{
+	int i, j, h = height, w = width;
+	int shift = (8 - (height % 8)) & 7;
+
+	width = (width + 7) & ~7;
+	height = (height + 7) & ~7;
+
+	for (i = 0; i < h; i++) {
+		for (j = 0; j < w; j++) {
+			if (pattern_test_bit(j, i, width, in))
+				pattern_set_bit(height - 1 - i - shift, j,
+						height, out);
+		}
+	}
+}
+
+/**
+ * font_glyph_rotate_90 - Rotate a glyph pattern by 90° in clockwise direction
+ * @glyph: The glyph to rotate
+ * @width: The glyph width in bits per scanline
+ * @height: The number of scanlines in the glyph
+ * @out: The rotated glyph bitmap
+ *
+ * The parameters @width and @height refer to the input glyph given in @glyph.
+ * The caller has to provide the output buffer @out of sufficient size to hold
+ * the rotated glyph. Rotating by 90° flips the width and height for the output
+ * glyph. Depending on the glyph pitch, the size of the output glyph can be
+ * different than the size of the input. Callers have to take this into account
+ * when allocating the output memory.
+ */
+void font_glyph_rotate_90(const unsigned char *glyph, unsigned int width, unsigned int height,
+			  unsigned char *out)
+{
+	memset(out, 0, font_glyph_size(height, width)); /* flip width/height */
+
+	rotate_cw(glyph, out, width, height);
+}
+EXPORT_SYMBOL_GPL(font_glyph_rotate_90);
+
+static inline void rotate_ud(const char *in, char *out, u32 width, u32 height)
+{
+	int i, j;
+	int shift = (8 - (width % 8)) & 7;
+
+	width = (width + 7) & ~7;
+
+	for (i = 0; i < height; i++) {
+		for (j = 0; j < width - shift; j++) {
+			if (pattern_test_bit(j, i, width, in))
+				pattern_set_bit(width - (1 + j + shift),
+						height - (1 + i),
+						width, out);
+		}
+	}
+}
+
+/**
+ * font_glyph_rotate_180 - Rotate a glyph pattern by 180°
+ * @glyph: The glyph to rotate
+ * @width: The glyph width in bits per scanline
+ * @height: The number of scanlines in the glyph
+ * @out: The rotated glyph bitmap
+ *
+ * The parameters @width and @height refer to the input glyph given in @glyph.
+ * The caller has to provide the output buffer @out of sufficient size to hold
+ * the rotated glyph.
+ */
+void font_glyph_rotate_180(const unsigned char *glyph, unsigned int width, unsigned int height,
+			   unsigned char *out)
+{
+	memset(out, 0, font_glyph_size(width, height));
+
+	rotate_ud(glyph, out, width, height);
+}
+EXPORT_SYMBOL_GPL(font_glyph_rotate_180);
+
+static inline void rotate_ccw(const char *in, char *out, u32 width, u32 height)
+{
+	int i, j, h = height, w = width;
+	int shift = (8 - (width % 8)) & 7;
+
+	width = (width + 7) & ~7;
+	height = (height + 7) & ~7;
+
+	for (i = 0; i < h; i++) {
+		for (j = 0; j < w; j++) {
+			if (pattern_test_bit(j, i, width, in))
+				pattern_set_bit(i, width - 1 - j - shift,
+						height, out);
+		}
+	}
+}
+
+/**
+ * font_glyph_rotate_270 - Rotate a glyph pattern by 270° in clockwise direction
+ * @glyph: The glyph to rotate
+ * @width: The glyph width in bits per scanline
+ * @height: The number of scanlines in the glyph
+ * @out: The rotated glyph bitmap
+ *
+ * The parameters @width and @height refer to the input glyph given in @glyph.
+ * The caller has to provide the output buffer @out of sufficient size to hold
+ * the rotated glyph. Rotating by 270° flips the width and height for the output
+ * glyph. Depending on the glyph pitch, the size of the output glyph can be
+ * different than the size of the input. Callers have to take this into account
+ * when allocating the output memory.
+ */
+void font_glyph_rotate_270(const unsigned char *glyph, unsigned int width, unsigned int height,
+			   unsigned char *out)
+{
+	memset(out, 0, font_glyph_size(height, width)); /* flip width/height */
+
+	rotate_ccw(glyph, out, width, height);
+}
+EXPORT_SYMBOL_GPL(font_glyph_rotate_270);