rm3100/setup.sh

#!/usr/bin/env bash
#
# One-time system setup for the CH347 USB-I2C adapter and the RM3100 logger.
# Idempotent: safe to re-run.
#
# Needs sudo for exactly one thing: installing the udev rule that grants this
# user access to the adapter's USB node.

set -euo pipefail

VID=1a86
PID=55db
RULE_FILE=/etc/udev/rules.d/99-ch347.rules

cd "$(dirname "$0")"

echo "== 1. Checking for the CH347 adapter =="
if ! lsusb -d "$VID:$PID" >/dev/null 2>&1; then
    echo "ERROR: no device $VID:$PID found on the USB bus." >&2
    echo "       Plug in the Waveshare adapter and make sure it is in Mode 1" >&2
    echo "       (UART1+I2C+SPI): DTR1 pulled high, RTS1 pulled low." >&2
    exit 1
fi
lsusb -d "$VID:$PID"

echo
echo "== 2. Installing udev rule =="
# Access is granted two ways, because no single mechanism covers every distro:
#
#   TAG+="uaccess"   systemd-logind puts an ACL on the node for whoever is
#                    logged in at the local seat. Needs no group and no logout,
#                    and is the only thing that works unaided on atomic Fedora
#                    (Bazzite, Silverblue, Kinoite) -- see section 4.
#   GROUP=/MODE=     the traditional fallback, for ssh sessions and seatless
#                    systems where there is no local seat for uaccess to grant.
#
# The group is picked from those that exist. plugdev is a Debian convention and
# is absent on Fedora; naming a group that does not exist makes udev log an
# error and leave the node owned by root, which is worse than omitting it.
ACCESS_GROUP=""
for g in plugdev dialout; do
    if getent group "$g" >/dev/null; then ACCESS_GROUP=$g; break; fi
done

RULE="SUBSYSTEM==\"usb\", ATTRS{idVendor}==\"$VID\", ATTRS{idProduct}==\"$PID\", TAG+=\"uaccess\""
if [[ -n "$ACCESS_GROUP" ]]; then
    RULE="$RULE, GROUP=\"$ACCESS_GROUP\", MODE=\"0660\""
    echo "Access via uaccess, falling back to group '$ACCESS_GROUP'."
else
    echo "No plugdev or dialout group here; relying on uaccess alone."
fi

if [[ -f "$RULE_FILE" ]] && [[ "$(cat "$RULE_FILE")" == "$RULE" ]]; then
    echo "$RULE_FILE already up to date, skipping."
else
    echo "Writing $RULE_FILE (needs sudo)..."
    printf '%s\n' "$RULE" | sudo tee "$RULE_FILE" >/dev/null
    sudo udevadm control --reload-rules
    # --action=add, not the default 'change': the uaccess builtin that sets the
    # ACL only runs on add, so a change event would install the rule without
    # granting anything until the next replug. Matched to this device alone so
    # re-running setup does not re-add every USB device on the system.
    sudo udevadm trigger --action=add --subsystem-match=usb \
         --attr-match=idVendor="$VID" --attr-match=idProduct="$PID"
    # trigger returns before the rule has necessarily been applied.
    sudo udevadm settle
    echo "Installed."
fi

echo
echo "== 3. Creating virtualenv and installing pyusb =="
if [[ ! -d .venv ]]; then
    python3 -m venv .venv
    echo "Created .venv"
else
    echo ".venv already exists"
fi
./.venv/bin/pip install --quiet --upgrade pip
./.venv/bin/pip install --quiet pyusb
echo "pyusb $(./.venv/bin/python -c 'import usb; print(usb.__version__)') installed"

echo
echo "== 4. Verifying device node permissions =="
# The node itself is the ground truth, so nothing above is warned about
# speculatively -- group membership only matters if uaccess did not already
# cover it, and that is visible here.
NODE=$(lsusb -d "$VID:$PID" | head -1 |
       sed -E 's|Bus ([0-9]+) Device ([0-9]+).*|/dev/bus/usb/\1/\2|')
ls -l "$NODE"
getfacl -p "$NODE" 2>/dev/null | grep -E "^user:[^:]+:" || true

if [[ -w "$NODE" ]]; then
    echo "OK: $NODE is writable by $(id -un)."
else
    USER_NAME=$(id -un)
    echo "WARNING: $NODE is not writable by $USER_NAME." >&2
    echo >&2
    echo "  uaccess grants nothing over ssh or without a local seat, so fall" >&2
    echo "  back to the group. Try, in order:" >&2
    echo >&2
    echo "  1. Unplug and replug the adapter, so the rule applies to a fresh" >&2
    echo "     node. This is enough on a local desktop session." >&2
    if [[ -n "$ACCESS_GROUP" ]] &&
       ! id -nG | tr ' ' '\n' | grep -qx "$ACCESS_GROUP"; then
        echo >&2
        if [[ -f /run/ostree-booted ]]; then
            # usermod edits /etc/group directly, while getent also sees
            # /usr/lib/group through nss_altfiles. On rpm-ostree systems the
            # group is often only in the latter, so it looks present to every
            # query and still fails to add: "group '$ACCESS_GROUP' does not
            # exist". Copying the line across is what makes usermod agree.
            echo "  2. This is an rpm-ostree system (Bazzite/Silverblue), where" >&2
            echo "     '$ACCESS_GROUP' may exist only in /usr/lib/group. usermod" >&2
            echo "     reads /etc/group alone and will refuse. Copy it over:" >&2
            echo "         grep -E '^$ACCESS_GROUP:' /usr/lib/group | sudo tee -a /etc/group" >&2
            echo "     then:" >&2
        else
            echo "  2. Add yourself to the group:" >&2
        fi
        echo "         sudo usermod -aG $ACCESS_GROUP $USER_NAME" >&2
        echo "     and log out and back in for it to take effect." >&2
    fi
fi

echo
echo "Setup complete. Run the logger with:"
echo "    ./.venv/bin/python logger.py --duration 10"
echo "or, to check wiring only:"
echo "    ./.venv/bin/python logger.py --scan-only"