Re: [PATCH v2 00/13] vc,fbcon,fonts: Proper handling of font data

[Thomas Zimmermann <tzimmermann@suse.de>]

Hi

Am 03.03.26 um 16:29 schrieb Helge Deller:
> On 3/2/26 15:08, 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.
>>
>> 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: Compare font data for equality with font_data_is_equal()
>>    lib/fonts: Manage font-data lifetime with font_data_get/_put()
>>    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                   | 236 +++++++++++++++++++++++++++-
>>   24 files changed, 518 insertions(+), 267 deletions(-)
>>   create mode 100644 lib/fonts/font.h
> Thomas, thanks for the nice cleanup!
> Beside a few minor comments which I posted to the various patches, the 
> series looks good.
>
> I've applied it for further testing to the fbdev git tree.

Great, thanks!

> In case you send later v3 series, I'll update it.

I'd preferably not modify the data structures for now. Shall I send an 
update for the typos?

Best regards
Thomas

>
> Thanks a lot!
> Helge

-- 
--
Thomas Zimmermann
Graphics Driver Developer
SUSE Software Solutions Germany GmbH
Frankenstr. 146, 90461 Nürnberg, Germany, www.suse.com
GF: Jochen Jaser, Andrew McDonald, Werner Knoblich, (HRB 36809, AG Nürnberg)