vt: Store font in struct vc_font

Replace struct console_font with struct vc_font for the type of the
vc_font field of struct vc_data. Struct console_font is UAPI, which
prevents further changes. Hence a new data type is required.

Struct console_font has a documented vertical pitch of 32 bytes. This
is not the case after the font data has been loaded into the kernel.
Changing the type of vc_font addresses this inconsistency.

The font data is now declared as constant, as it might come from the
kernel's read-only section. There's some fallout throughout the console
code where non-const variables refer to it. Fix them. A later update
will declare the font data to a dedicated data type.

v3:
- fix typos

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

drivers/video/fbdev/core/bitblit.c

@@ -22,8 +22,7 @@
 /*
  * Accelerated handlers.
  */
-static void update_attr(u8 *dst, u8 *src, int attribute,
-			       struct vc_data *vc)
+static void update_attr(u8 *dst, const u8 *src, int attribute, struct vc_data *vc)
 {
 	int i, offset = (vc->vc_font.height < 10) ? 1 : 2;
 	int width = DIV_ROUND_UP(vc->vc_font.width, 8);
@@ -81,7 +80,7 @@ static inline void bit_putcs_aligned(struct vc_data *vc, struct fb_info *info,
 	u16 charmask = vc->vc_hi_font_mask ? 0x1ff : 0xff;
 	unsigned int charcnt = vc->vc_font.charcount;
 	u32 idx = vc->vc_font.width >> 3;
-	u8 *src;
+	const u8 *src;
 
 	while (cnt--) {
 		u16 ch = scr_readw(s++) & charmask;
@@ -120,7 +119,7 @@ static inline void bit_putcs_unaligned(struct vc_data *vc,
 	u32 shift_low = 0, mod = vc->vc_font.width % 8;
 	u32 shift_high = 8;
 	u32 idx = vc->vc_font.width >> 3;
-	u8 *src;
+	const u8 *src;
 
 	while (cnt--) {
 		u16 ch = scr_readw(s++) & charmask;
@@ -267,7 +266,7 @@ static void bit_cursor(struct vc_data *vc, struct fb_info *info, bool enable,
 	int y = real_y(par->p, vc->state.y);
 	int attribute, use_sw = vc->vc_cursor_type & CUR_SW;
 	int err = 1;
-	char *src;
+	const u8 *src;
 
 	cursor.set = 0;
 
@@ -278,7 +277,7 @@ static void bit_cursor(struct vc_data *vc, struct fb_info *info, bool enable,
 	attribute = get_attribute(info, c);
 	src = vc->vc_font.data + ((c & charmask) * (w * vc->vc_font.height));
 
-	if (par->cursor_state.image.data != src ||
+	if (par->cursor_state.image.data != (const char *)src ||
 	    par->cursor_reset) {
 		par->cursor_state.image.data = src;
 		cursor.set |= FB_CUR_SETIMAGE;

drivers/video/fbdev/core/fbcon.c

@@ -2286,7 +2286,7 @@ static bool fbcon_blank(struct vc_data *vc, enum vesa_blank_mode blank,
 
 static int fbcon_get_font(struct vc_data *vc, struct console_font *font, unsigned int vpitch)
 {
-	u8 *fontdata = vc->vc_font.data;
+	const u8 *fontdata = vc->vc_font.data;
 	u8 *data = font->data;
 	int i, j;
 
@@ -2417,7 +2417,7 @@ static int fbcon_do_set_font(struct vc_data *vc, int w, int h, int charcount,
 	struct fbcon_par *par = info->fbcon_par;
 	struct fbcon_display *p = &fb_display[vc->vc_num];
 	int resize, ret, old_userfont, old_width, old_height, old_charcount;
-	u8 *old_data = vc->vc_font.data;
+	const u8 *old_data = vc->vc_font.data;
 
 	resize = (w != vc->vc_font.width) || (h != vc->vc_font.height);
 	vc->vc_font.data = (void *)(p->fontdata = data);

drivers/video/fbdev/core/fbcon.h

@@ -82,8 +82,8 @@ struct fbcon_par {
 	int    rotate;
 	int    cur_rotate;
 	char  *cursor_data;
-	u8    *fontbuffer;
-	u8    *fontdata;
+	u8          *fontbuffer;
+	const u8    *fontdata;
 	u8    *cursor_src;
 	u32    cursor_size;
 	u32    fd_size;

include/linux/console_struct.h

@@ -13,8 +13,9 @@
 #ifndef _LINUX_CONSOLE_STRUCT_H
 #define _LINUX_CONSOLE_STRUCT_H
 
-#include <linux/wait.h>
+#include <linux/math.h>
 #include <linux/vt.h>
+#include <linux/wait.h>
 #include <linux/workqueue.h>
 
 struct uni_pagedict;
@@ -58,6 +59,30 @@ struct vc_state {
 	bool		reverse;
 };
 
+/**
+ * struct vc_font - Describes a font
+ * @width: The width of a single glyph in bits
+ * @height: The height of a single glyph in scanlines
+ * @charcount: The number of glyphs in the font
+ * @data: The raw font data
+ *
+ * Font data is organized as an array of glyphs. Each glyph is a bitmap with
+ * set bits indicating the foreground color. Unset bits indicate background
+ * color. The fields @width and @height store a single glyph's number of
+ * horizontal bits and vertical scanlines. If width is not a multiple of 8,
+ * there are trailing bits to fill up the byte. These bits should not be drawn.
+ *
+ * The field @data points to the first glyph's first byte. The value @charcount
+ * gives the number of glyphs in the font. There are no empty scanlines between
+ * two adjacent glyphs.
+ */
+struct vc_font {
+	unsigned int width;
+	unsigned int height;
+	unsigned int charcount;
+	const unsigned char *data;
+};
+
 /*
  * Example: vc_data of a console that was scrolled 3 lines down.
  *
@@ -122,7 +147,7 @@ struct vc_data {
 	unsigned long	vc_pos;			/* Cursor address */
 	/* fonts */
 	unsigned short	vc_hi_font_mask;	/* [#] Attribute set for upper 256 chars of font or 0 if not supported */
-	struct console_font vc_font;		/* Current VC font set */
+	struct vc_font vc_font;			/* Current VC font set */
 	unsigned short	vc_video_erase_char;	/* Background erase character */
 	/* VT terminal data */
 	unsigned int	vc_state;		/* Escape sequence parser state */