Re: [PATCH v3 00/13] vc,fbcon,fonts: Proper handling of font data

[Helge Deller <deller@gmx.de>]

On 3/9/26 15:14, Thomas Zimmermann wrote:
> Provide helpers for handling console font data. Update consoles and VT.
> 
> VT's vc_state stores font data as a plain byte array of glphys. Fbcon,
> newport_con and the kernel's internal fonts store the glyph data as an
> array of plain bytes plus a hidden header for reference counting, check
> sums and buffer sizes. The reference counting only works for user-space
> fonts but not for internal fonts. Font-data handling is duplicated in
> several places. Most of the font handling is open-coded and mixed up with
> VT's plain glyph arrays.
> 
> To address these issues, add proper handling of font data to all involved
> components: struct vc_font for font state in VC; a font data type for the
> consoles. Then implement interfaces for handling font data one by one.
> 
> Patch 1 prepares the fbdev interface.
> 
> Patches 2 to 4 prepare VT's font handling.
> 
> Patches 5 to 13 refactor fbcon and newport_con to use clean interfaces for
> their fonts.
> 
> Fbcon has long been a source of problems and bug reports. [1] With its
> confusing implementation, it is hard to find the cause of these bugs.
> Cleaning up the fbcon code will hopefully help with resolving bug reports
> in the future.
> 
> The series has been tested with fbcon under DRM's bochs driver by changing
> fonts at runtime using the setfont utility. [2] The changes to newport_con
> have only been tested to compile.
> 
> v3:
> - fix module font linking (Nathan, Arnd)
> - fix typos (Helge)
> - clarify return value of font_data_put()
> v2:
> - keep declaring the internal fonts in the public header file (Helge)
> - rebase and clean up
> 
> [1] https://lore.kernel.org/all/6992c84c.a70a0220.2c38d7.00e8.GAE@google.com/
> [2] https://www.man7.org/linux/man-pages/man8/setfont.8.html
> 
> Thomas Zimmermann (13):
>    fbdev: Declare src parameter of fb_pad_ helpers as constant
>    vt: Remove trailing whitespaces
>    vt: Store font in struct vc_font
>    vt: Calculate font-buffer size with vc_font_size()
>    lib/fonts: Remove trailing whitespaces
>    lib/fonts: Remove FNTCHARCNT()
>    lib/fonts: Store font data as font_data_t; update consoles
>    lib/fonts: Read font size with font_data_size()
>    lib/fonts: Manage font-data lifetime with font_data_get/_put()
>    lib/fonts: Compare font data for equality with font_data_is_equal()
>    lib/fonts: Create font_data_t from struct console_font with
>      font_data_import()
>    lib/fonts: Store font data for user space with font_data_export()
>    lib/fonts: Remove internal symbols and macros from public header file
> 
>   drivers/video/console/newport_con.c |  61 +++-----
>   drivers/video/fbdev/core/bitblit.c  |  11 +-
>   drivers/video/fbdev/core/fbcon.c    | 194 +++++++----------------
>   drivers/video/fbdev/core/fbcon.h    |   8 +-
>   drivers/video/fbdev/core/fbmem.c    |   6 +-
>   include/linux/console_struct.h      |  59 ++++++-
>   include/linux/fb.h                  |  10 +-
>   include/linux/font.h                | 115 +++++++++-----
>   lib/fonts/font.h                    |  38 +++++
>   lib/fonts/font_10x18.c              |   2 +-
>   lib/fonts/font_6x10.c               |   3 +-
>   lib/fonts/font_6x11.c               |   2 +-
>   lib/fonts/font_6x8.c                |   3 +-
>   lib/fonts/font_7x14.c               |   2 +-
>   lib/fonts/font_8x16.c               |   3 +-
>   lib/fonts/font_8x8.c                |   2 +-
>   lib/fonts/font_acorn_8x8.c          |   4 +-
>   lib/fonts/font_mini_4x6.c           |  10 +-
>   lib/fonts/font_pearl_8x8.c          |   2 +-
>   lib/fonts/font_sun12x22.c           |   3 +-
>   lib/fonts/font_sun8x16.c            |   3 +-
>   lib/fonts/font_ter10x18.c           |   4 +-
>   lib/fonts/font_ter16x32.c           |   4 +-
>   lib/fonts/fonts.c                   | 232 +++++++++++++++++++++++++++-
>   24 files changed, 514 insertions(+), 267 deletions(-)
>   create mode 100644 lib/fonts/font.h

series applied to fbdev git tree.

Thanks!
Helge