[BRLTTY] Linux console hacking (was: Re: Footsteps towards better accessibility in Linux)

[Nicolas Pitre]

On Fri, 27 Mar 2026, Sébastien Hinderer wrote:

> Nicolas Pitre (2026/03/26 21:45 -0400):
> > This is now available in kernels v6.18.20 or later, v6.19.10 or later,
> > and the upcoming v7.0.
> >
> > Disclaimer: Someone else contributed this support to v6.18.0 but it was
> > completely broken for /dev/vcsu users like BRLTTY. This prompted me to
> > finally look at it and contribute a fix, hence those kernel versions
> > above.
> 
> Thank you so much for the time, work and efforts you dedicate to this,
> Nicolas.
> 
> Once the kernel has been updated, is there anything more to do so that
> applications actually take advantage of this, or are things going to
> "just work"?

You need to update the "linux" terminfo entry. This script should do it:

=====
#!/bin/sh
set -e

WORK=$(mktemp /tmp/terminfo-XXXXXX.ti)
trap 'rm -f "$WORK"' EXIT

infocmp "linux" > "$WORK"

# Check if already patched
if grep -q 'smcup' "$WORK"; then
    echo "smcup/rmcup already present, nothing to do."
    exit 0
fi

# Insert smcup/rmcup before the closing entry (last capability line)
sed -i 's/\(.*\),$/\1,\n\tsmcup=\\E[?1049h, rmcup=\\E[?1049l,/' "$WORK"

echo "Compiling patched terminfo entry..."
tic -x "$WORK"
=====

This installs the patched entry to ~/.terminfo (user-only, no root 
needed). For a system-wide install, change the tic line to:

sudo tic -x -o /usr/share/terminfo "$WORK"


Nicolas