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feat(deploy): services.bitspire.nfc.enable — declare the reader per machine

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pcscd was enabled in hardware/batm3.nix and hardware/upboard.nix, which
cannot express "is a reader fitted": upboard.nix is shared by sintra (HID
Global OMNIKEY 5022) and tejo (nothing fitted), so tejo inherited pcscd it
has no use for, while the douro — with its own hardware file — got none and
wedged on every boot.

Make it a machine capability instead. services.bitspire.nfc.enable owns
pcscd, the two polkit rules and the wedge-recovery unit, and hands the app
a BITSPIRE_NFC_ENABLED flag so it doesn't initialise nfc-pcsc at all on a
machine with no reader. Per-model truth lives in nfcReaderForModel in
flake.nix next to fiatCodeForModel and upgradeWindowForModel, since a
shared hardware file can't answer the question. batm3 and sintra are true;
douro and tejo flip to true when readers are fitted.

The flag goes through the unit's Environment rather than
/var/lib/bitspire/.env, because .env is only written when absent — a
machine provisioned months ago would never pick up a new value.
This commit is contained in:
Padreug 2026-09-29 22:49:59 +02:00
commit bb2ad39628
5 changed files with 137 additions and 95 deletions
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63
deploy/nixos/hardware/batm3.nix
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@ -85,65 +85,10 @@
cpuFreqGovernor = "performance";
};
# PC/SC daemon for the Feitian KP382 contactless reader (096e:0608, a CCID
# smart-card reader) used for Bolt Card tap-to-pay on cash-out. Enabling it
# binds the CCID driver to the reader; the app talks to pcscd's socket (via
# nfc-pcsc) rather than the USB device directly. Harmless if no reader is
# attached — pcscd just idles.
services.pcscd.enable = true;
# pcscd gates client access via polkit; without a rule the sandboxed
# `bitspire` service user is "Rejected unauthorized PC/SC client". Authorize
# it to talk to the daemon and the card. The second rule lets the app trigger
# the NFC reader wedge-recovery service (see nfc-reader-reset below).
security.polkit.extraConfig = ''
polkit.addRule(function(action, subject) {
if ((action.id == "org.debian.pcsc-lite.access_pcsc" ||
action.id == "org.debian.pcsc-lite.access_card") &&
subject.user == "bitspire") {
return polkit.Result.YES;
}
});
polkit.addRule(function(action, subject) {
if (action.id == "org.freedesktop.systemd1.manage-units" &&
action.lookup("unit") == "nfc-reader-reset.service" &&
subject.user == "bitspire") {
return polkit.Result.YES;
}
});
'';
# NFC reader wedge-recovery. The Feitian R502-CL CCID reader (and, less often,
# any CCID reader) can wedge: it keeps detecting a card but every APDU returns
# "card absent or mute", and ONLY a USB power-cycle clears it — restarting
# pcscd or the app does not. This oneshot re-binds the reader's USB device (a
# software replug); pcscd + nfc-pcsc then re-detect it on hotplug with no app
# restart (verified on-device). The app (unprivileged `bitspire`) starts it via
# the polkit rule above when it sees repeated read failures. Reader-agnostic:
# it matches the USB CCID interface class (0x0B), so it also covers a future
# ACR1252U swap without a config change.
systemd.services.nfc-reader-reset = {
description = "Power-cycle a wedged CCID NFC reader (USB re-bind)";
serviceConfig = {
Type = "oneshot";
ExecStart = pkgs.writeShellScript "reset-nfc-reader" ''
set -u
found=0
for iface in /sys/bus/usb/devices/*:*/bInterfaceClass; do
[ -f "$iface" ] || continue
[ "$(${pkgs.coreutils}/bin/cat "$iface" 2>/dev/null)" = "0b" ] || continue
ifname=$(${pkgs.coreutils}/bin/basename "$(${pkgs.coreutils}/bin/dirname "$iface")")
dev=''${ifname%%:*}
echo "reset-nfc-reader: power-cycling CCID reader USB device $dev" >&2
echo -n "$dev" > /sys/bus/usb/drivers/usb/unbind 2>/dev/null || true
${pkgs.coreutils}/bin/sleep 2
echo -n "$dev" > /sys/bus/usb/drivers/usb/bind 2>/dev/null || true
found=1
done
[ "$found" = 1 ] || { echo "reset-nfc-reader: no CCID reader found" >&2; exit 1; }
'';
};
};
# The Feitian KP382 contactless reader (096e:0608) is declared as a machine
# capability, not here: `nfcReaderForModel` in flake.nix drives
# services.bitspire.nfc.enable, which owns pcscd, the polkit rules and the
# wedge-recovery unit (deploy/nixos/bitspire-atm.nix).
# Disable suspend/hibernate for kiosk
systemd.targets = {