[PATCH 08/10] lib/fonts: Implement font rotation

@@ -86,7 +86,7 @@ struct fbcon_par {
 	const u8    *fontdata;
 	u8    *cursor_src;
 	u32    cursor_size;
-	u32    fd_size;
+	size_t fd_size;
 
 	const struct fbcon_bitops *bitops;
 };

@@ -8,84 +8,44 @@
  *  more details.
  */
 
-#include <linux/module.h>
-#include <linux/slab.h>
-#include <linux/string.h>
+#include <linux/errno.h>
 #include <linux/fb.h>
 #include <linux/font.h>
-#include <linux/vt_kern.h>
-#include <linux/console.h>
-#include <asm/types.h>
+
 #include "fbcon.h"
 #include "fbcon_rotate.h"
 
 int fbcon_rotate_font(struct fb_info *info, struct vc_data *vc)
 {
 	struct fbcon_par *par = info->fbcon_par;
-	int len, err = 0;
-	int s_cellsize, d_cellsize, i;
-	const u8 *src;
-	u8 *dst;
+	unsigned char *fontbuffer;
+	int ret;
 
 	if (vc->vc_font.data == par->fontdata &&
 	    par->p->con_rotate == par->cur_rotate)
-		goto finished;
+		return 0;
 
-	src = par->fontdata = vc->vc_font.data;
+	par->fontdata = vc->vc_font.data;
 	par->cur_rotate = par->p->con_rotate;
-	len = vc->vc_font.charcount;
-	s_cellsize = font_glyph_size(vc->vc_font.width, vc->vc_font.height);
-	d_cellsize = s_cellsize;
-
-	if (par->rotate == FB_ROTATE_CW ||
-	    par->rotate == FB_ROTATE_CCW)
-		d_cellsize = font_glyph_size(vc->vc_font.height, vc->vc_font.width);
 
 	if (info->fbops->fb_sync)
 		info->fbops->fb_sync(info);
 
-	if (par->fd_size < d_cellsize * len) {
-		kfree(par->fontbuffer);
-		par->fontbuffer = NULL;
-		par->fd_size = 0;
-
-		dst = kmalloc_array(len, d_cellsize, GFP_KERNEL);
-
-		if (dst == NULL) {
-			err = -ENOMEM;
-			goto finished;
-		}
-
-		par->fd_size = d_cellsize * len;
-		par->fontbuffer = dst;
+	fontbuffer = font_data_rotate(par->p->fontdata, vc->vc_font.width,
+				      vc->vc_font.height, vc->vc_font.charcount,
+				      par->rotate, par->fontbuffer, &par->fd_size);
+	if (IS_ERR(fontbuffer)) {
+		ret = PTR_ERR(fontbuffer);
+		goto err_kfree;
 	}
 
-	dst = par->fontbuffer;
+	par->fontbuffer = fontbuffer;
 
-	switch (par->rotate) {
-	case FB_ROTATE_UD:
-		for (i = len; i--; ) {
-			font_glyph_rotate_180(src, vc->vc_font.width, vc->vc_font.height, dst);
-			src += s_cellsize;
-			dst += d_cellsize;
-		}
-		break;
-	case FB_ROTATE_CW:
-		for (i = len; i--; ) {
-			font_glyph_rotate_90(src, vc->vc_font.width, vc->vc_font.height, dst);
-			src += s_cellsize;
-			dst += d_cellsize;
-		}
-		break;
-	case FB_ROTATE_CCW:
-		for (i = len; i--; ) {
-			font_glyph_rotate_270(src, vc->vc_font.width, vc->vc_font.height, dst);
-			src += s_cellsize;
-			dst += d_cellsize;
-		}
-		break;
-	}
+	return 0;
+
+err_kfree:
+	kfree(par->fontbuffer);
+	par->fontbuffer = NULL; /* clear here to avoid output */
 
-finished:
-	return err;
+	return ret;
 }

@@ -111,6 +111,9 @@ void font_glyph_rotate_180(const unsigned char *glyph, unsigned int width, unsig
 			   unsigned char *out);
 void font_glyph_rotate_270(const unsigned char *glyph, unsigned int width, unsigned int height,
 			   unsigned char *out);
+unsigned char *font_data_rotate(font_data_t *fd, unsigned int width, unsigned int height,
+				unsigned int charcount, unsigned int steps,
+				unsigned char *buf, size_t *bufsize);
 
 /*
  * Font description

@@ -9,8 +9,11 @@
  * more details.
  */
 
+#include <linux/errno.h>
 #include <linux/export.h>
 #include <linux/math.h>
+#include <linux/overflow.h>
+#include <linux/slab.h>
 #include <linux/string.h>
 
 #include "font.h"

@@ -170,3 +173,103 @@ void font_glyph_rotate_270(const unsigned char *glyph, unsigned int width, unsig
 	__font_glyph_rotate_270(glyph, width, height, out);
 }
 EXPORT_SYMBOL_GPL(font_glyph_rotate_270);
+
+/**
+ * font_data_rotate - Rotate font data by multiples of 90°
+ * @fd: The font data to rotate
+ * @width: The glyph width in bits per scanline
+ * @height: The number of scanlines in the glyph
+ * @charcount: The number of glyphs in the font
+ * @steps: Number of rotation steps of 90°
+ * @buf: Preallocated output buffer; can be NULL
+ * @bufsize: The size of @buf in bytes; can be NULL
+ *
+ * The parameters @width and @height refer to the visible number of pixels
+ * and scanlines in a single glyph. The number of glyphs is given in @charcount.
+ * Rotation happens in steps of 90°. The @steps parameter can have any value,
+ * but only 0 to 3 produce distinct results. With 4 or higher, a full rotation
+ * has been performed. You can pass any value for @steps and the helper will
+ * perform the appropriate rotation. Note that the returned buffer is not
+ * compatible with font_data_t. It only contains glphy data in the same format
+ * as returned by font_data_buf(). Callers are responsible to free the returned
+ * buffer with kfree(). Font rotation typically happens when displays get
+ * re-oriented. To avoid unnecessary re-allocation of the memory buffer, the
+ * caller can pass in an earlier result buffer in @buf for reuse. The buffer
+ * size of given and returned in @bufsize. The allocation semantics are compatible
+ * with krealloc().
+ *
+ * Returns:
+ * A buffer with rotated glyphs on success, or an error pointer otherwise
+ */
+unsigned char *font_data_rotate(font_data_t *fd, unsigned int width, unsigned int height,
+				unsigned int charcount, unsigned int steps,
+				unsigned char *buf, size_t *bufsize)
+{
+	const unsigned char *src = font_data_buf(fd);
+	unsigned int s_cellsize = font_glyph_size(width, height);
+	unsigned int d_cellsize, i;
+	unsigned char *dst;
+	size_t size;
+
+	steps %= 4;
+
+	switch (steps) {
+	case 0:
+	case 2:
+		d_cellsize = s_cellsize;
+		break;
+	case 1:
+	case 3:
+		d_cellsize = font_glyph_size(height, width); /* flip width/height */
+		break;
+	}
+
+	if (check_mul_overflow(charcount, d_cellsize, &size))
+		return ERR_PTR(-EINVAL);
+
+	if (!buf || !bufsize || size > *bufsize) {
+		dst = kmalloc_array(charcount, d_cellsize, GFP_KERNEL);
+		if (!dst)
+			return ERR_PTR(-ENOMEM);
+
+		kfree(buf);
+		buf = dst;
+		if (bufsize)
+			*bufsize = size;
+	} else {
+		dst = buf;
+	}
+
+	switch (steps) {
+	case 0:
+		memcpy(dst, src, size);
+		break;
+	case 1:
+		memset(dst, 0, size);
+		for (i = 0; i < charcount; ++i) {
+			__font_glyph_rotate_90(src, width, height, dst);
+			src += s_cellsize;
+			dst += d_cellsize;
+		}
+		break;
+	case 2:
+		memset(dst, 0, size);
+		for (i = 0; i < charcount; ++i) {
+			__font_glyph_rotate_180(src, width, height, dst);
+			src += s_cellsize;
+			dst += d_cellsize;
+		}
+		break;
+	case 3:
+		memset(dst, 0, size);
+		for (i = 0; i < charcount; ++i) {
+			__font_glyph_rotate_270(src, width, height, dst);
+			src += s_cellsize;
+			dst += d_cellsize;
+		}
+		break;
+	}
+
+	return buf;
+}
+EXPORT_SYMBOL_GPL(font_data_rotate);