XPost: linux.debian.bugs.dist   
   From: wbkernel@gmail.com   
      
   After some more digging, the problem is probably when the font is   
   assigned in the following file:   
   drivers/video/fbdev/core/fbcon.c   
   Somewhere around line 1011, maybe.  Line 1009 hardcodes the charcount   
   to 256.  Later kernels set this to the actual font size sometime   
   around 2020.  Two commits found in this area in the 6.1.120 kernel   
   applied cleanly, but did not compile.  Specifically, the following   
   commits were applied in order, first a1ac250a82a5e97, then commit   
   17d649967006f.   
   .   
   However, for the purposes of the 5.10, it looks like the value is   
   hardcoded to 256.  So, rather than fix this properly, just hardcoding   
   the value as is is probably sufficient.   
   .   
   I will try a build later with a hardcoded fix.   
   .   
   a1ac250a82a5e97: fbcon: Avoid using FNTCHARCNT() and hard-coded   
   built-in font charcount   
   17d649967006f: Revert "fbcon: don't lose the console font across   
   generic->chip driver switch"   
   .   
      
   On Fri, Dec 26, 2025 at 10:07 PM William Burrow  wrote:   
   >   
   > Hi, did some more work.   
   > The problem with changing the variable, ch, to any fixed value is that   
   > when charcnt is 0, then whatever is being evaluated is clobbered.  The   
   > reason for charcount being zero must be fixed.  The following log was   
   > produced from the diff shown at the end of this message (only   
   > bit_putcs_aligned() seems to be called):   
   > .   
   > -------------------------- log -------------------------   
   > 2025-12-26T20:30:02.666098-04:00 abc kernel: [   52.640518] ** **   
   > bit_putcs_aligned: ---------->>   
   > 2025-12-26T20:30:02.666099-04:00 abc kernel: [   52.640518] ** **   
   > bit_putcs_aligned: cnt: 12   
   > 2025-12-26T20:30:02.666100-04:00 abc kernel: [   52.640519] ** **   
   > bit_putcs_aligned: vc->vc_font.data: 0xffff932c008a8010   
   > 2025-12-26T20:30:02.666101-04:00 abc kernel: [   52.640519] ** **   
   > bit_putcs_aligned:          srcorig: 0xffff932c008a8210   
   > 2025-12-26T20:30:02.666102-04:00 abc kernel: [   52.640520] ** **   
   > bit_putcs_aligned: before: ch: 0x20   
   > 2025-12-26T20:30:02.666103-04:00 abc kernel: [   52.640520] ** **   
   > bit_putcs_aligned:  after: ch: 0x20   
   > 2025-12-26T20:30:02.666104-04:00 abc kernel: [   52.640521] ** **   
   > bit_putcs_aligned: charcnt: 0x0   
   > 2025-12-26T20:30:02.666104-04:00 abc kernel: [   52.640522] ** **   
   > bit_putcs_aligned: cellsize: 0x10   
   > 2025-12-26T20:30:02.666105-04:00 abc kernel: [   52.640522] ** **   
   > bit_putcs_aligned: ch * cellsize: 0x200   
   > 2025-12-26T20:30:02.666106-04:00 abc kernel: [   52.640523] ** **   
   > bit_putcs_aligned:           srcnew: 0xffff932c008a8210   
   > 2025-12-26T20:30:02.666107-04:00 abc kernel: [   52.640523] ** **   
   > bit_putcs_aligned: srcorig - srcnew: 0x0   
   > 2025-12-26T20:30:02.666108-04:00 abc kernel: [   52.640525] ** **   
   > bit_putcs_aligned: srcnew   
   > 2025-12-26T20:30:02.666109-04:00 abc kernel: [   52.640525] ** **   
   > bit_putcs_aligned: <<----------   
   > 2025-12-26T20:30:02.666110-04:00 abc kernel: [   52.640526] ** **   
   > bit_putcs_aligned: ---------->>   
   > 2025-12-26T20:30:02.666121-04:00 abc kernel: [   52.640526] ** **   
   > bit_putcs_aligned: cnt: 11   
   > 2025-12-26T20:30:02.666123-04:00 abc kernel: [   52.640527] ** **   
   > bit_putcs_aligned: vc->vc_font.data: 0xffff932c008a8010   
   > 2025-12-26T20:30:02.666124-04:00 abc kernel: [   52.640527] ** **   
   > bit_putcs_aligned:          srcorig: 0xffff932c008a8320   
   > 2025-12-26T20:30:02.666125-04:00 abc kernel: [   52.640528] ** **   
   > bit_putcs_aligned: before: ch: 0x31   
   > 2025-12-26T20:30:02.666125-04:00 abc kernel: [   52.640528] ** **   
   > bit_putcs_aligned:  after: ch: 0x20          <<<--- CLOBBERED   
   > 2025-12-26T20:30:02.666126-04:00 abc kernel: [   52.640529] ** **   
   > bit_putcs_aligned: charcnt: 0x0   
   > 2025-12-26T20:30:02.666127-04:00 abc kernel: [   52.640529] ** **   
   > bit_putcs_aligned: cellsize: 0x10   
   > 2025-12-26T20:30:02.666128-04:00 abc kernel: [   52.640530] ** **   
   > bit_putcs_aligned: ch * cellsize: 0x200   
   > 2025-12-26T20:30:02.666129-04:00 abc kernel: [   52.640530] ** **   
   > bit_putcs_aligned:           srcnew:   
   > 0xffffjjjjjjjjjjjjjjjjj932c008a8210   
   > 2025-12-26T20:30:02.666130-04:00 abc kernel: [   52.640531] ** **   
   > bit_putcs_aligned: srcorig - srcnew: 0x110   
   > 2025-12-26T20:30:02.666130-04:00 abc kernel: [   52.640531] ** **   
   > bit_putcs_aligned: srcnew   
   > 2025-12-26T20:30:02.666132-04:00 abc kernel: [   52.640531] ** **   
   > bit_putcs_aligned: <<----------   
   > -------------------------- log -------------------------   
   > .   
      
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