Re: 5.15 regression: CONFIG_SYSFB_SIMPLEFB breaks console scrolling

[Thorsten Leemhuis]

Hi, this is your Linux kernel regression tracker speaking.

On 16.11.21 05:52, Harald Dunkel wrote:
> 
> if I enable CONFIG_SYSFB_SIMPLEFB in 5.15.2 and use grub's default
> configuration
> (Debian sid amd64), then a few lines at the bottom of /dev/tty1 including
> login prompt are off-screen. Scrolling is broken. I can login, though.
> 
> Enabling GRUB_TERMINAL=console in grub doesn't make a difference. Using
> the same kernel except for CONFIG_SYSFB_SIMPLEFB the problem is gone.
> 
> Graphics card is a GeForce GTX 1650. I tried with both CONFIG_DRM_NOUVEAU
> and proprietary graphics drivers disabled.
> 
> Attached you can find the config file. Please mail if I can help to track
> this problem down.

Thx for the report. I'm not totally sure if this is a regression, as
that's a new config option. But it might be one considered a successor
to an older one, hence it might count as regression. Adding two
developers and a mailing list to the CC, hopefully someone can clarify.

TWIMC: To be sure this issue doesn't fall through the cracks unnoticed,
I'm adding it to regzbot, my Linux kernel regression tracking bot:

#regzbot ^introduced 8633ef82f101c040427b57d4df7b706261420b94
#regzbot title CONFIG_SYSFB_SIMPLEFB breaks console scrolling
#regzbot ignore-activity

Ciao, Thorsten, your Linux kernel regression tracker.

P.S.: If you want to know more about regzbot, check out its
web-interface, the getting start guide, and/or the references documentation:

https://linux-regtracking.leemhuis.info/regzbot/
https://gitlab.com/knurd42/regzbot/-/blob/main/docs/getting_started.md
https://gitlab.com/knurd42/regzbot/-/blob/main/docs/reference.md

The last two documents will explain how you can interact with regzbot
yourself if your want to.

Hint for the reporter: when reporting a regression it's in your interest
to tell #regzbot about it in the report, as that will ensure the
regression gets on the radar of regzbot and the regression tracker.
That's in your interest, as they will make sure the report won't fall
through the cracks unnoticed.

Hint for developers: you normally don't need to care about regzbot, just
fix the issue as you normally would. Just remember to include a 'Link:'
tag to the report in the commit message, as explained in
Documentation/process/submitting-patches.rst
That aspect was recently was made more explicit in commit 1f57bd42b77c:
https://git.kernel.org/linus/1f57bd42b77c