lib/fonts: Add font_glyph_cursor() helper

The new helper font_glyph_cursor() fills a glyph with a cursor pattern.
As with the font_glyph_rotate_*() helpers, the caller has to provide the
output memory.

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

include/linux/font.h

@@ -109,6 +109,10 @@ const unsigned char *font_data_glyph_buf(font_data_t *fd,
 bool font_data_is_equal(font_data_t *lhs, font_data_t *rhs);
 int font_data_export(font_data_t *fd, struct console_font *font, unsigned int vpitch);
 
+/* font_cursor.c */
+void font_glyph_cursor(unsigned int width, unsigned int height,
+		       unsigned int from, unsigned int to, unsigned char *out);
+
 /* font_rotate.c */
 void font_glyph_rotate_90(const unsigned char *glyph, unsigned int width, unsigned int height,
 			  unsigned char *out);

lib/fonts/Makefile

@@ -1,7 +1,8 @@
 # SPDX-License-Identifier: GPL-2.0
 # Font handling
 
-font-y := fonts.o
+font-y := fonts.o \
+	  font_cursor.o
 font-$(CONFIG_FRAMEBUFFER_CONSOLE_ROTATION) += font_rotate.o
 
 # Built-in fonts; sorted by Family-Size in ascending order

lib/fonts/font_cursor.c

@@ -0,0 +1,56 @@
+// SPDX-License-Identifier: GPL-2.0-only
+
+#include <linux/bug.h>
+#include <linux/export.h>
+#include <linux/string.h>
+
+#include "font.h"
+
+/**
+ * font_glyph_cursor - Create a cursor glyph
+ * @width: The glyph width in bits per scanline
+ * @height: The number of scanlines in the glyph
+ * @start: The first scanline of the cursor block
+ * @end: The first scanline after the cursor block
+ * @out: The cursor-glyph bitmap
+ *
+ * The parameters @width and @height refer to the glyph size. The caller
+ * has to provide the output buffer @out of sufficient size to hold the
+ * cursor glyph. The arguments in @start and @end describe the number of
+ * scanlines occupied by the cursor block; counting from the top of the
+ * glyph. The helper fills these scanlines with a pattern and clears the
+ * remaining scanlines.
+ */
+void font_glyph_cursor(unsigned int width, unsigned int height,
+		       unsigned int start, unsigned int end, unsigned char *out)
+{
+	unsigned int pitch = font_glyph_pitch(width);
+	const unsigned char *out_end = out + height * pitch;
+	unsigned int size;
+
+	if (WARN_ON_ONCE(start > height))
+		start = height;
+	if (WARN_ON_ONCE(end > height))
+		end = height;
+
+	if (end < start)
+		end = start;
+
+	/* clear scanlines before cursor block */
+	size = start * pitch;
+	memset(out, 0x00, size);
+	out += size;
+
+	/* set cursor block */
+	size = (end - start) * pitch;
+	memset(out, 0xff, size);
+	out += size;
+
+	/* clear scanlines below cursor block */
+	size = (height - end) * pitch;
+	memset(out, 0x00, size);
+	out += size;
+
+	WARN_ON_ONCE(out != out_end);
+}
+EXPORT_SYMBOL_GPL(font_glyph_cursor);