[PATCH 03/10] lib/fonts: Provide helpers for calculating glyph pitch and size

Thomas Zimmermann
2026-03-27T13:04:43Z

Implement pitch and size calculation for a single font glyph in the
new helpers font_glyph_pitch() and font_glyph_size(). Replace the
instances where the calculations are opencoded.

Note that in the case of fbcon console rotation, the parameters for
a glyph's width and height might be reversed. This is intentionally.

Signed-off-by: Thomas Zimmermann <tzimmermann@suse.de>
---
drivers/tty/vt/vt.c | 5 ++--
drivers/video/fbdev/core/fbcon_ccw.c | 11 +++----
drivers/video/fbdev/core/fbcon_cw.c | 11 +++----
drivers/video/fbdev/core/fbcon_rotate.c | 6 ++--
drivers/video/fbdev/core/fbcon_ud.c | 7 +++--
include/linux/font.h | 40 +++++++++++++++++++++++++
lib/fonts/fonts.c | 2 +-
7 files changed, 61 insertions(+), 21 deletions(-)

diff --git a/drivers/tty/vt/vt.c b/drivers/tty/vt/vt.c
index 3d89d30c9596..23b9683b52a5 100644
--- a/drivers/tty/vt/vt.c
+++ b/drivers/tty/vt/vt.c
@@ -71,7 +71,6 @@
* by Adam Tla/lka <atlka@pg.gda.pl>, Aug 2006
*/

-#include <linux/math.h>
#include <linux/module.h>
#include <linux/types.h>
#include <linux/sched/signal.h>
@@ -244,7 +243,7 @@ enum {
*/
unsigned int vc_font_pitch(const struct vc_font *font)
{
- return DIV_ROUND_UP(font->width, 8);
+ return font_glyph_pitch(font->width);
}
EXPORT_SYMBOL_GPL(vc_font_pitch);

@@ -261,7 +260,7 @@ EXPORT_SYMBOL_GPL(vc_font_pitch);
*/
unsigned int vc_font_size(const struct vc_font *font)
{
- return font->height * vc_font_pitch(font) * font->charcount;
+ return font_glyph_size(font->width, font->height) * font->charcount;
}
EXPORT_SYMBOL_GPL(vc_font_size);

diff --git a/drivers/video/fbdev/core/fbcon_ccw.c b/drivers/video/fbdev/core/fbcon_ccw.c
index 2f394b5a17f7..96ef449ee6ac 100644
--- a/drivers/video/fbdev/core/fbcon_ccw.c
+++ b/drivers/video/fbdev/core/fbcon_ccw.c
@@ -26,7 +26,7 @@ static void ccw_update_attr(u8 *dst, u8 *src, int attribute,
struct vc_data *vc)
{
int i, j, offset = (vc->vc_font.height < 10) ? 1 : 2;
- int width = (vc->vc_font.height + 7) >> 3;
+ int width = font_glyph_pitch(vc->vc_font.height);
int mod = vc->vc_font.height % 8;
u8 c, msk = ~(0xff << offset), msk1 = 0;

@@ -101,7 +101,7 @@ static inline void ccw_putcs_aligned(struct vc_data *vc, struct fb_info *info,
{
struct fbcon_par *par = info->fbcon_par;
u16 charmask = vc->vc_hi_font_mask ? 0x1ff : 0xff;
- u32 idx = (vc->vc_font.height + 7) >> 3;
+ u32 idx = font_glyph_pitch(vc->vc_font.height);
u8 *src;

while (cnt--) {
@@ -131,7 +131,7 @@ static void ccw_putcs(struct vc_data *vc, struct fb_info *info,
{
struct fb_image image;
struct fbcon_par *par = info->fbcon_par;
- u32 width = (vc->vc_font.height + 7)/8;
+ u32 width = font_glyph_pitch(vc->vc_font.height);
u32 cellsize = width * vc->vc_font.width;
u32 maxcnt = info->pixmap.size/cellsize;
u32 scan_align = info->pixmap.scan_align - 1;
@@ -223,7 +223,8 @@ static void ccw_cursor(struct vc_data *vc, struct fb_info *info, bool enable,
struct fb_cursor cursor;
struct fbcon_par *par = info->fbcon_par;
unsigned short charmask = vc->vc_hi_font_mask ? 0x1ff : 0xff;
- int w = (vc->vc_font.height + 7) >> 3, c;
+ int w = font_glyph_pitch(vc->vc_font.height);
+ int c;
int y = real_y(par->p, vc->state.y);
int attribute, use_sw = vc->vc_cursor_type & CUR_SW;
int err = 1, dx, dy;
@@ -297,7 +298,7 @@ static void ccw_cursor(struct vc_data *vc, struct fb_info *info, bool enable,
char *tmp, *mask = kmalloc_array(w, vc->vc_font.width,
GFP_ATOMIC);
int cur_height, size, i = 0;
- int width = (vc->vc_font.width + 7)/8;
+ int width = font_glyph_pitch(vc->vc_font.width);

if (!mask)
return;
diff --git a/drivers/video/fbdev/core/fbcon_cw.c b/drivers/video/fbdev/core/fbcon_cw.c
index 3c3ad3471ec4..ea712654edae 100644
--- a/drivers/video/fbdev/core/fbcon_cw.c
+++ b/drivers/video/fbdev/core/fbcon_cw.c
@@ -26,7 +26,7 @@ static void cw_update_attr(u8 *dst, u8 *src, int attribute,
struct vc_data *vc)
{
int i, j, offset = (vc->vc_font.height < 10) ? 1 : 2;
- int width = (vc->vc_font.height + 7) >> 3;
+ int width = font_glyph_pitch(vc->vc_font.height);
u8 c, msk = ~(0xff >> offset);

for (i = 0; i < vc->vc_font.width; i++) {
@@ -86,7 +86,7 @@ static inline void cw_putcs_aligned(struct vc_data *vc, struct fb_info *info,
{
struct fbcon_par *par = info->fbcon_par;
u16 charmask = vc->vc_hi_font_mask ? 0x1ff : 0xff;
- u32 idx = (vc->vc_font.height + 7) >> 3;
+ u32 idx = font_glyph_pitch(vc->vc_font.height);
u8 *src;

while (cnt--) {
@@ -116,7 +116,7 @@ static void cw_putcs(struct vc_data *vc, struct fb_info *info,
{
struct fb_image image;
struct fbcon_par *par = info->fbcon_par;
- u32 width = (vc->vc_font.height + 7)/8;
+ u32 width = font_glyph_pitch(vc->vc_font.height);
u32 cellsize = width * vc->vc_font.width;
u32 maxcnt = info->pixmap.size/cellsize;
u32 scan_align = info->pixmap.scan_align - 1;
@@ -206,7 +206,8 @@ static void cw_cursor(struct vc_data *vc, struct fb_info *info, bool enable,
struct fb_cursor cursor;
struct fbcon_par *par = info->fbcon_par;
unsigned short charmask = vc->vc_hi_font_mask ? 0x1ff : 0xff;
- int w = (vc->vc_font.height + 7) >> 3, c;
+ int w = font_glyph_pitch(vc->vc_font.height);
+ int c;
int y = real_y(par->p, vc->state.y);
int attribute, use_sw = vc->vc_cursor_type & CUR_SW;
int err = 1, dx, dy;
@@ -280,7 +281,7 @@ static void cw_cursor(struct vc_data *vc, struct fb_info *info, bool enable,
char *tmp, *mask = kmalloc_array(w, vc->vc_font.width,
GFP_ATOMIC);
int cur_height, size, i = 0;
- int width = (vc->vc_font.width + 7)/8;
+ int width = font_glyph_pitch(vc->vc_font.width);

if (!mask)
return;
diff --git a/drivers/video/fbdev/core/fbcon_rotate.c b/drivers/video/fbdev/core/fbcon_rotate.c
index 5348f6c6f57c..18575c5182db 100644
--- a/drivers/video/fbdev/core/fbcon_rotate.c
+++ b/drivers/video/fbdev/core/fbcon_rotate.c
@@ -33,14 +33,12 @@ int fbcon_rotate_font(struct fb_info *info, struct vc_data *vc)
src = par->fontdata = vc->vc_font.data;
par->cur_rotate = par->p->con_rotate;
len = vc->vc_font.charcount;
- s_cellsize = ((vc->vc_font.width + 7)/8) *
- vc->vc_font.height;
+ 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 = ((vc->vc_font.height + 7)/8) *
- vc->vc_font.width;
+ d_cellsize = font_glyph_size(vc->vc_font.height, vc->vc_font.width);

if (info->fbops->fb_sync)
info->fbops->fb_sync(info);
diff --git a/drivers/video/fbdev/core/fbcon_ud.c b/drivers/video/fbdev/core/fbcon_ud.c
index 6fc30cad5b19..f7cd89c42b01 100644
--- a/drivers/video/fbdev/core/fbcon_ud.c
+++ b/drivers/video/fbdev/core/fbcon_ud.c
@@ -26,7 +26,7 @@ static void ud_update_attr(u8 *dst, u8 *src, int attribute,
struct vc_data *vc)
{
int i, offset = (vc->vc_font.height < 10) ? 1 : 2;
- int width = (vc->vc_font.width + 7) >> 3;
+ int width = font_glyph_pitch(vc->vc_font.width);
unsigned int cellsize = vc->vc_font.height * width;
u8 c;

@@ -153,7 +153,7 @@ static void ud_putcs(struct vc_data *vc, struct fb_info *info,
{
struct fb_image image;
struct fbcon_par *par = info->fbcon_par;
- u32 width = (vc->vc_font.width + 7)/8;
+ u32 width = font_glyph_pitch(vc->vc_font.width);
u32 cellsize = width * vc->vc_font.height;
u32 maxcnt = info->pixmap.size/cellsize;
u32 scan_align = info->pixmap.scan_align - 1;
@@ -253,7 +253,8 @@ static void ud_cursor(struct vc_data *vc, struct fb_info *info, bool enable,
struct fb_cursor cursor;
struct fbcon_par *par = info->fbcon_par;
unsigned short charmask = vc->vc_hi_font_mask ? 0x1ff : 0xff;
- int w = (vc->vc_font.width + 7) >> 3, c;
+ int w = font_glyph_pitch(vc->vc_font.width);
+ int c;
int y = real_y(par->p, vc->state.y);
int attribute, use_sw = vc->vc_cursor_type & CUR_SW;
int err = 1, dx, dy;
diff --git a/include/linux/font.h b/include/linux/font.h
index 5401f07dd6ce..3bd49d914b22 100644
--- a/include/linux/font.h
+++ b/include/linux/font.h
@@ -11,10 +11,50 @@
#ifndef _VIDEO_FONT_H
#define _VIDEO_FONT_H

+#include <linux/math.h>
#include <linux/types.h>

struct console_font;

+/*
+ * Glyphs
+ */
+
+/**
+ * font_glyph_pitch - Calculates the number of bytes per scanline
+ * @width: The glyph width in bits per scanline
+ *
+ * A glyph's pitch is the number of bytes in a single scanline, rounded
+ * up to the next full byte. The parameter @width receives the number
+ * of visible bits per scanline. For example, if width is 14 bytes per
+ * scanline, the pitch is 2 bytes per scanline. If width is 8 bits per
+ * scanline, the pitch is 1 byte per scanline.
+ *
+ * Returns:
+ * The number of bytes in a single scanline of the glyph
+ */
+static inline unsigned int font_glyph_pitch(unsigned int width)
+{
+ return DIV_ROUND_UP(width, 8);
+}
+
+/**
+ * font_glyph_size - Calculates the number of bytes per glyph
+ * @width: The glyph width in bits per scanline
+ * @vpitch: The number of scanlines in the glyph
+ *
+ * The number of bytes in a glyph depends on the pitch and the number
+ * of scanlines. font_glyph_size automatically calculates the pitch
+ * from the given width. The parameter @vpitch gives the number of
+ * scanlines, which is usually the glyph's height in scanlines. Fonts
+ * coming from user space can sometimes have a different vertical pitch
+ * with empty scanlines between two adjacent glyphs.
+ */
+static inline unsigned int font_glyph_size(unsigned int width, unsigned int vpitch)
+{
+ return font_glyph_pitch(width) * vpitch;
+}
+
/*
* font_data_t and helpers
*/
diff --git a/lib/fonts/fonts.c b/lib/fonts/fonts.c
index 5938f542906b..f5d5333450a0 100644
--- a/lib/fonts/fonts.c
+++ b/lib/fonts/fonts.c
@@ -26,7 +26,7 @@

#include "font.h"

-#define console_font_pitch(font) DIV_ROUND_UP((font)->width, 8)
+#define console_font_pitch(font) font_glyph_pitch((font)->width)

/*
* Helpers for font_data_t
--
2.53.0