[PATCH v3 RFC 5/5] fbcon: Avoid using FNTCHARCNT() and hard-coded built-in font charcount

From: Peilin Ye
Date: Thu Nov 12 2020 - 07:16:15 EST

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For user-provided fonts, the framebuffer layer is using a magic
negative-indexing macro, FNTCHARCNT(), to keep track of their number of
characters:

#define FNTCHARCNT(fd) (((int *)(fd))[-3])

For built-in fonts, it is using hard-coded values (256). This results in
something like the following:

map.length = (ops->p->userfont) ?
FNTCHARCNT(ops->p->fontdata) : 256;

This is unsatisfactory. In fact, there is already a `charcount` field in
our virtual console descriptor (see `struct console_font` inside `struct
vc_data`), let us use it:

map.length = vc->vc_font.charcount;

Recently we added a `charcount` field to `struct font_desc`. Use it to set
`vc->vc_font.charcount` properly. The idea is:

- We only use FNTCHARCNT() on `vc->vc_font.data` and `p->fontdata`.
Assume FNTCHARCNT() is working as intended;
- Whenever `vc->vc_font.data` is set, also set `vc->vc_font.charcount`
properly;
- We can now replace `FNTCHARCNT(vc->vc_font.data)` with
`vc->vc_font.charcount`;
- Since `p->fontdata` always point to the same font data buffer with
`vc->vc_font.data`, we can also replace `FNTCHARCNT(p->fontdata)` with
`vc->vc_font.charcount`.

In conclusion, set `vc->vc_font.charcount` properly in fbcon_startup(),
fbcon_init(), fbcon_set_disp() and fbcon_do_set_font(), then replace
FNTCHARCNT() with `vc->vc_font.charcount`. No more if-else between
negative-indexing macros and hard-coded values.

Do not include <linux/font.h> in fbcon_rotate.c and tileblit.c, since they
no longer need it.

Depends on patch "Fonts: Add charcount field to font_desc".

Suggested-by: Daniel Vetter <daniel@xxxxxxxx>
Signed-off-by: Peilin Ye <yepeilin.cs@xxxxxxxxx>
---
v2: https://lore.kernel.org/lkml/20201028155139.1220549-1-yepeilin.cs@xxxxxxxxx/

Boot-tested only, thus the "RFC". Looking forward to suggestions about how
to test this properly. Thank you!

I am not very sure about the statement "`p->fontdata` always point to the
same font data buffer with `vc->vc_font.data`". It is concluded from code
reading.

Change in v3:
- Do not touch fbcon_copy_font() since we removed it in patch "console:
Delete unused con_font_copy() callback implementations"

Changes in v2:
- Try avoid using FNTCHARCNT() altogether, instead of only changing a
little bit (Daniel)
- Set `vc->vc_font.charcount` properly, in fbcon_startup(),
fbcon_init(), fbcon_set_disp() and fbcon_do_set_font()
- Replace hard-coded 256 whenever possible

drivers/video/fbdev/core/fbcon.c | 57 +++++++++----------------
drivers/video/fbdev/core/fbcon_rotate.c | 3 +-
drivers/video/fbdev/core/tileblit.c | 4 +-
3 files changed, 23 insertions(+), 41 deletions(-)

diff --git a/drivers/video/fbdev/core/fbcon.c b/drivers/video/fbdev/core/fbcon.c
index 26d1b0916692..06520667fc07 100644
--- a/drivers/video/fbdev/core/fbcon.c
+++ b/drivers/video/fbdev/core/fbcon.c
@@ -1004,7 +1004,7 @@ static const char *fbcon_startup(void)
vc->vc_font.width = font->width;
vc->vc_font.height = font->height;
vc->vc_font.data = (void *)(p->fontdata = font->data);
- vc->vc_font.charcount = 256; /* FIXME Need to support more fonts */
+ vc->vc_font.charcount = font->charcount;
} else {
p->fontdata = vc->vc_font.data;
}
@@ -1032,7 +1032,7 @@ static void fbcon_init(struct vc_data *vc, int init)
struct vc_data **default_mode = vc->vc_display_fg;
struct vc_data *svc = *default_mode;
struct fbcon_display *t, *p = &fb_display[vc->vc_num];
- int logo = 1, new_rows, new_cols, rows, cols, charcnt = 256;
+ int logo = 1, new_rows, new_cols, rows, cols;
int cap, ret;

if (WARN_ON(info_idx == -1))
@@ -1068,6 +1068,7 @@ static void fbcon_init(struct vc_data *vc, int init)
fvc->vc_font.data);
vc->vc_font.width = fvc->vc_font.width;
vc->vc_font.height = fvc->vc_font.height;
+ vc->vc_font.charcount = fvc->vc_font.charcount;
p->userfont = t->userfont;

if (p->userfont)
@@ -1083,17 +1084,13 @@ static void fbcon_init(struct vc_data *vc, int init)
vc->vc_font.width = font->width;
vc->vc_font.height = font->height;
vc->vc_font.data = (void *)(p->fontdata = font->data);
- vc->vc_font.charcount = 256; /* FIXME Need to
- support more fonts */
+ vc->vc_font.charcount = font->charcount;
}
}

- if (p->userfont)
- charcnt = FNTCHARCNT(p->fontdata);
-
vc->vc_can_do_color = (fb_get_color_depth(&info->var, &info->fix)!=1);
vc->vc_complement_mask = vc->vc_can_do_color ? 0x7700 : 0x0800;
- if (charcnt == 256) {
+ if (vc->vc_font.charcount == 256) {
vc->vc_hi_font_mask = 0;
} else {
vc->vc_hi_font_mask = 0x100;
@@ -1358,7 +1355,7 @@ static void fbcon_set_disp(struct fb_info *info, struct fb_var_screeninfo *var,
struct vc_data **default_mode, *vc;
struct vc_data *svc;
struct fbcon_ops *ops = info->fbcon_par;
- int rows, cols, charcnt = 256;
+ int rows, cols;

p = &fb_display[unit];

@@ -1378,12 +1375,11 @@ static void fbcon_set_disp(struct fb_info *info, struct fb_var_screeninfo *var,
vc->vc_font.data = (void *)(p->fontdata = t->fontdata);
vc->vc_font.width = (*default_mode)->vc_font.width;
vc->vc_font.height = (*default_mode)->vc_font.height;
+ vc->vc_font.charcount = (*default_mode)->vc_font.charcount;
p->userfont = t->userfont;
if (p->userfont)
REFCOUNT(p->fontdata)++;
}
- if (p->userfont)
- charcnt = FNTCHARCNT(p->fontdata);

var->activate = FB_ACTIVATE_NOW;
info->var.activate = var->activate;
@@ -1393,7 +1389,7 @@ static void fbcon_set_disp(struct fb_info *info, struct fb_var_screeninfo *var,
ops->var = info->var;
vc->vc_can_do_color = (fb_get_color_depth(&info->var, &info->fix)!=1);
vc->vc_complement_mask = vc->vc_can_do_color ? 0x7700 : 0x0800;
- if (charcnt == 256) {
+ if (vc->vc_font.charcount == 256) {
vc->vc_hi_font_mask = 0;
} else {
vc->vc_hi_font_mask = 0x100;
@@ -2027,7 +2023,7 @@ static int fbcon_resize(struct vc_data *vc, unsigned int width,
*/
if (pitch <= 0)
return -EINVAL;
- size = CALC_FONTSZ(vc->vc_font.height, pitch, FNTCHARCNT(vc->vc_font.data));
+ size = CALC_FONTSZ(vc->vc_font.height, pitch, vc->vc_font.charcount);
if (size > FNTSIZE(vc->vc_font.data))
return -EINVAL;
}
@@ -2075,7 +2071,7 @@ static int fbcon_switch(struct vc_data *vc)
struct fbcon_ops *ops;
struct fbcon_display *p = &fb_display[vc->vc_num];
struct fb_var_screeninfo var;
- int i, ret, prev_console, charcnt = 256;
+ int i, ret, prev_console;

info = registered_fb[con2fb_map[vc->vc_num]];
ops = info->fbcon_par;
@@ -2152,10 +2148,7 @@ static int fbcon_switch(struct vc_data *vc)
vc->vc_can_do_color = (fb_get_color_depth(&info->var, &info->fix)!=1);
vc->vc_complement_mask = vc->vc_can_do_color ? 0x7700 : 0x0800;

- if (p->userfont)
- charcnt = FNTCHARCNT(vc->vc_font.data);
-
- if (charcnt > 256)
+ if (vc->vc_font.charcount > 256)
vc->vc_complement_mask <<= 1;

updatescrollmode(p, info, vc);
@@ -2405,31 +2398,27 @@ static void set_vc_hi_font(struct vc_data *vc, bool set)
}
}

-static int fbcon_do_set_font(struct vc_data *vc, int w, int h,
+static int fbcon_do_set_font(struct vc_data *vc, int w, int h, int charcount,
const u8 * data, int userfont)
{
struct fb_info *info = registered_fb[con2fb_map[vc->vc_num]];
struct fbcon_ops *ops = info->fbcon_par;
struct fbcon_display *p = &fb_display[vc->vc_num];
int resize;
- int cnt;
char *old_data = NULL;

resize = (w != vc->vc_font.width) || (h != vc->vc_font.height);
if (p->userfont)
old_data = vc->vc_font.data;
- if (userfont)
- cnt = FNTCHARCNT(data);
- else
- cnt = 256;
vc->vc_font.data = (void *)(p->fontdata = data);
if ((p->userfont = userfont))
REFCOUNT(data)++;
vc->vc_font.width = w;
vc->vc_font.height = h;
- if (vc->vc_hi_font_mask && cnt == 256)
+ vc->vc_font.charcount = charcount;
+ if (vc->vc_hi_font_mask && charcount == 256)
set_vc_hi_font(vc, false);
- else if (!vc->vc_hi_font_mask && cnt == 512)
+ else if (!vc->vc_hi_font_mask && charcount == 512)
set_vc_hi_font(vc, true);

if (resize) {
@@ -2496,9 +2485,10 @@ static int fbcon_set_font(struct vc_data *vc, struct console_font *font,
if (!new_data)
return -ENOMEM;

+ memset(new_data, 0, FONT_EXTRA_WORDS * sizeof(int));
+
new_data += FONT_EXTRA_WORDS * sizeof(int);
FNTSIZE(new_data) = size;
- FNTCHARCNT(new_data) = charcount;
REFCOUNT(new_data) = 0; /* usage counter */
for (i=0; i< charcount; i++) {
memcpy(new_data + i*h*pitch, data + i*32*pitch, h*pitch);
@@ -2524,7 +2514,7 @@ static int fbcon_set_font(struct vc_data *vc, struct console_font *font,
break;
}
}
- return fbcon_do_set_font(vc, font->width, font->height, new_data, 1);
+ return fbcon_do_set_font(vc, font->width, font->height, charcount, new_data, 1);
}

static int fbcon_set_def_font(struct vc_data *vc, struct console_font *font, char *name)
@@ -2540,7 +2530,7 @@ static int fbcon_set_def_font(struct vc_data *vc, struct console_font *font, cha

font->width = f->width;
font->height = f->height;
- return fbcon_do_set_font(vc, f->width, f->height, f->data, 0);
+ return fbcon_do_set_font(vc, f->width, f->height, f->charcount, f->data, 0);
}

static u16 palette_red[16];
@@ -3009,7 +2999,6 @@ void fbcon_get_requirement(struct fb_info *info,
struct fb_blit_caps *caps)
{
struct vc_data *vc;
- struct fbcon_display *p;

if (caps->flags) {
int i, charcnt;
@@ -3018,11 +3007,9 @@ void fbcon_get_requirement(struct fb_info *info,
vc = vc_cons[i].d;
if (vc && vc->vc_mode == KD_TEXT &&
info->node == con2fb_map[i]) {
- p = &fb_display[i];
caps->x |= 1 << (vc->vc_font.width - 1);
caps->y |= 1 << (vc->vc_font.height - 1);
- charcnt = (p->userfont) ?
- FNTCHARCNT(p->fontdata) : 256;
+ charcnt = vc->vc_font.charcount;
if (caps->len < charcnt)
caps->len = charcnt;
}
@@ -3032,11 +3019,9 @@ void fbcon_get_requirement(struct fb_info *info,

if (vc && vc->vc_mode == KD_TEXT &&
info->node == con2fb_map[fg_console]) {
- p = &fb_display[fg_console];
caps->x = 1 << (vc->vc_font.width - 1);
caps->y = 1 << (vc->vc_font.height - 1);
- caps->len = (p->userfont) ?
- FNTCHARCNT(p->fontdata) : 256;
+ caps->len = vc->vc_font.charcount;
}
}
}
diff --git a/drivers/video/fbdev/core/fbcon_rotate.c b/drivers/video/fbdev/core/fbcon_rotate.c
index ac72d4f85f7d..ef1d421c261a 100644
--- a/drivers/video/fbdev/core/fbcon_rotate.c
+++ b/drivers/video/fbdev/core/fbcon_rotate.c
@@ -14,7 +14,6 @@
#include <linux/fb.h>
#include <linux/vt_kern.h>
#include <linux/console.h>
-#include <linux/font.h>
#include <asm/types.h>
#include "fbcon.h"
#include "fbcon_rotate.h"
@@ -33,7 +32,7 @@ static int fbcon_rotate_font(struct fb_info *info, struct vc_data *vc)

src = ops->fontdata = vc->vc_font.data;
ops->cur_rotate = ops->p->con_rotate;
- len = (!ops->p->userfont) ? 256 : FNTCHARCNT(src);
+ len = vc->vc_font.charcount;
s_cellsize = ((vc->vc_font.width + 7)/8) *
vc->vc_font.height;
d_cellsize = s_cellsize;
diff --git a/drivers/video/fbdev/core/tileblit.c b/drivers/video/fbdev/core/tileblit.c
index 628fe5e010c0..e2cc0cb6d50e 100644
--- a/drivers/video/fbdev/core/tileblit.c
+++ b/drivers/video/fbdev/core/tileblit.c
@@ -13,7 +13,6 @@
#include <linux/fb.h>
#include <linux/vt_kern.h>
#include <linux/console.h>
-#include <linux/font.h>
#include <asm/types.h>
#include "fbcon.h"

@@ -145,8 +144,7 @@ void fbcon_set_tileops(struct vc_data *vc, struct fb_info *info)
map.width = vc->vc_font.width;
map.height = vc->vc_font.height;
map.depth = 1;
- map.length = (ops->p->userfont) ?
- FNTCHARCNT(ops->p->fontdata) : 256;
+ map.length = vc->vc_font.charcount;
map.data = ops->p->fontdata;
info->tileops->fb_settile(info, &map);
}
--
2.25.1

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