#!/bin/sh
# setup-i915-kernel7-fix.sh
#
# Run on a fresh hp-chell (HP Chromebook 13 "chell", coreboot/MrChromebox
# firmware, KDE neon) install to apply two things:
#
#   1. The kernel 7.x cold-boot black-screen workaround, which forces a
#      second modeset on eDP-1 to un-stick i915's pipe A on 7.x kernels:
#      a /usr/share/sddm/scripts/Xsetup hook (SDDM) and a
#      plasma-login.service drop-in doing a DPMS cycle (Plasma Login).
#      See project CLAUDE.md for the full diagnosis writeup.
#   2. GRUB_TIMEOUT=5 / GRUB_TIMEOUT_STYLE=menu, so the boot menu is
#      visible for 5 seconds (useful for picking a fallback kernel like
#      6.17.0-42-generic if a future 7.x point release regresses again).
#
# Safe to re-run; idempotent.

set -eu

if [ "$(id -u)" -ne 0 ]; then
    echo "must run as root (sudo $0)" >&2
    exit 1
fi

echo "==> installing SDDM Xsetup i915 kernel-7.x workaround"
cat > /usr/share/sddm/scripts/Xsetup << 'EOF'
#!/bin/sh
# Xsetup - run as root before the login dialog appears

if [ -e /sbin/prime-offload ]; then
    echo running NVIDIA Prime setup /sbin/prime-offload
    /sbin/prime-offload
fi

# Workaround: on kernel 7.x, the first i915 modeset at cold boot (Xorg's
# auto-modeset to the panel's native 3200x1800) leaves pipe A in a bad
# state (persistent CPU pipe A FIFO underrun -> blank panel, backlight
# still on, even though DRM/plane state reports healthy). Forcing a
# second modeset unsticks it. Rather than cycle back to native, just
# land on 1600x900 (exact half of 3200x1800, clean 2x integer scaling)
# and stay there -- it's only the login screen; the logged-in session
# renews the modeset itself and comes up at full native resolution.
# Not needed on 6.17.x kernels. See project CLAUDE.md for the full
# writeup.
case "$(uname -r)" in
    7.*)
        xrandr --output eDP-1 --mode 1600x900 >/tmp/xsetup-modeset.log 2>&1
        echo "set eDP-1 to 1600x900 (i915 kernel 7.x cold-boot workaround)"
        ;;
esac
EOF
chmod 755 /usr/share/sddm/scripts/Xsetup

# Plasma Login (plasmalogin, replaced SDDM on neon in 2026-09) runs its
# greeter under kwin_wayland, so the SDDM Xsetup hook above never fires.
# Equivalent fix there: a DPMS off/on cycle via kscreen-doctor, run from
# the greeter's own systemd user manager right after KWin comes up. A
# plain resolution change is NOT enough under KWin -- the eDP panel
# fitter absorbs it as a fastset without a real pipe modeset; DPMS off
# fully disables the CRTC so the "on" is a genuine full modeset.
echo "==> installing plasmalogin greeter i915 kernel-7.x workaround"
install -d /usr/local/libexec
cat > /usr/local/libexec/hp-chell-i915-dpms-cycle << 'EOF'
#!/bin/sh
# Run as the plasmalogin greeter user (from plasma-login.service's
# ExecStartPre). Forces a full modeset on kernel 7.x to un-stick i915
# pipe A after the cold-boot first modeset. See hp-chell CLAUDE.md.
case "$(uname -r)" in
    7.*) ;;
    *) exit 0 ;;
esac
[ "$(id -un)" = plasmalogin ] || exit 0

export WAYLAND_DISPLAY="${WAYLAND_DISPLAY:-wayland-0}"
export QT_QPA_PLATFORM=wayland

# wait (up to ~20s) for KWin's output management to answer
i=0
until kscreen-doctor -o >/dev/null 2>&1; do
    i=$((i + 1))
    [ "$i" -ge 40 ] && { echo "kscreen-doctor never came up" >&2; exit 0; }
    sleep 0.5
done

kscreen-doctor --dpms off >/dev/null 2>&1
sleep 1
kscreen-doctor --dpms on >/dev/null 2>&1
echo "cycled DPMS off/on (i915 kernel 7.x cold-boot workaround)"
EOF
chmod 755 /usr/local/libexec/hp-chell-i915-dpms-cycle

install -d /etc/systemd/user/plasma-login.service.d
cat > /etc/systemd/user/plasma-login.service.d/10-i915-kernel7-dpms-cycle.conf << 'EOF'
[Service]
ExecStartPre=-/usr/local/libexec/hp-chell-i915-dpms-cycle
EOF

echo "==> setting GRUB_TIMEOUT=5 / GRUB_TIMEOUT_STYLE=menu"
grub_conf=/etc/default/grub

set_grub_key() {
    key=$1
    value=$2
    if grep -q "^${key}=" "$grub_conf"; then
        sed -i "s|^${key}=.*|${key}=${value}|" "$grub_conf"
    elif grep -q "^#${key}=" "$grub_conf"; then
        sed -i "s|^#${key}=.*|${key}=${value}|" "$grub_conf"
    else
        echo "${key}=${value}" >> "$grub_conf"
    fi
}

set_grub_key GRUB_TIMEOUT 5
set_grub_key GRUB_TIMEOUT_STYLE menu

echo "==> running update-grub"
update-grub

echo "==> done"