#!/bin/sh
# som-console -- find the SOM's serial console among the USB-serial ports this
# machine was granted, and open it.
#
# The console of an Emcraft SOM carrier is the carrier's own USB-to-UART
# bridge: an FTDI FT232RL (0403:6001) on the SOM-BSB-EXT, a Silicon Labs CP2104
# (10c4:ea60) on the UCL-SOM-BSB starter kit. It reaches the guest as a WebUSB
# grant of its own, separate from the JTAG adapter, and ftdi_sio or cp210x binds
# it as a /dev/ttyUSB<n>. The number depends on grant order -- the Olimex's
# second interface is a UART too, and ftdi_sio takes a ttyUSB for it -- so the
# port is found by USB identity, never assumed. 0403:6001 is a generic FTDI id,
# so where two such bridges are granted, --serial names the one.
#
#   som-console              open the console in picocom (C-a C-x leaves)
#   som-console --find       print the device node and exit
#   som-console --list       list every USB-serial port with its identity
#
# Scripts (Expect, BRINTOS-12) take the node from --find:
#   spawn picocom -q -b 115200 [exec som-console --find]

set -u

PROG=som-console
IDS="${SOM_CONSOLE_ID:-0403:6001 10c4:ea60}"
SERIAL="${SOM_CONSOLE_SERIAL:-}"
BAUD="${SOM_CONSOLE_BAUD:-115200}"
# Overridable so the resolution can be exercised against a constructed tree.
SYSFS="${SOM_SYSFS:-/sys}"
DEVDIR="${SOM_DEVDIR:-/dev}"

mode=open
dev=""

usage() {
    cat <<EOF
usage: $PROG [--find | --list] [--id VID:PID] [--serial S] [--dev TTY] [--baud N]

  --find        print the console's device node and exit
  --list        list every USB-serial port: node, driver, VID:PID, serial
  --id VID:PID  the bridge to look for (default: $IDS --
                the SOM-BSB-EXT's FT232RL and the UCL-SOM-BSB's CP2104)
  --serial S    only the bridge with this USB serial number
  --dev TTY     skip the search and use TTY
  --baud N      line speed for the interactive session (default $BAUD)

With neither --find nor --list, opens the console in picocom; C-a C-x leaves.
EOF
}

while [ $# -gt 0 ]; do
    case "$1" in
        --find)  mode=find; shift ;;
        --list)  mode=list; shift ;;
        --id)    IDS=${2:-}; shift 2 || exit 2 ;;
        --serial) SERIAL=${2:-}; shift 2 || exit 2 ;;
        --dev)   dev=${2:-}; shift 2 || exit 2 ;;
        --baud)  BAUD=${2:-}; shift 2 || exit 2 ;;
        -h|--help) usage; exit 0 ;;
        *) echo "$PROG: unknown argument: $1" >&2; usage >&2; exit 2 ;;
    esac
done

for id in $IDS; do
    case "$id" in
        [0-9a-fA-F][0-9a-fA-F][0-9a-fA-F][0-9a-fA-F]:[0-9a-fA-F][0-9a-fA-F][0-9a-fA-F][0-9a-fA-F]) ;;
        *) echo "$PROG: --id wants VID:PID in hex, got '$id'" >&2; exit 2 ;;
    esac
done
IDS=$(printf '%s' "$IDS" | tr 'A-F' 'a-f')
WANT="$IDS${SERIAL:+ serial $SERIAL}"

# The ports that match: id among $IDS, and the serial if one was given.
matching() {
    ports | awk -v ids=" $IDS " -v ser="$SERIAL" \
        'index(ids, " " $3 " ") && (ser == "" || ($4 "") == (ser ""))'
}

# One line per USB-serial port: "<tty> <driver> <vid:pid> <serial>". The tty's
# sysfs node sits under its interface, and the interface under the USB device
# that carries idVendor/idProduct.
ports() {
    for t in "$SYSFS"/bus/usb-serial/devices/*; do
        [ -e "$t" ] || continue
        tty=${t##*/}
        real=$(cd -P "$t" 2>/dev/null && pwd -P) || continue
        usbdev=${real%/*}; usbdev=${usbdev%/*}
        vid=$(cat "$usbdev/idVendor" 2>/dev/null) || vid=????
        pid=$(cat "$usbdev/idProduct" 2>/dev/null) || pid=????
        ser=$(cat "$usbdev/serial" 2>/dev/null) || ser=-
        drv=-
        if [ -e "$t/driver" ]; then
            d=$(cd -P "$t/driver" 2>/dev/null && pwd -P) && drv=${d##*/}
        fi
        echo "$tty $drv $vid:$pid ${ser:--}"
    done
}

if [ "$mode" = list ]; then
    out=$(ports)
    if [ -z "$out" ]; then
        echo "$PROG: no USB-serial ports -- has the console adapter been granted to this machine?"
    else
        # echo, not printf: on the served runtime printf to a tty fails (rc=1, nothing shown) right after a child exits.
        echo "$out"
    fi
    exit 0
fi

if [ -z "$dev" ]; then
    hits=$(matching | awk '{ print $1 }')
    n=$(printf '%s' "$hits" | grep -c .)
    if [ "$n" -eq 0 ]; then
        echo "$PROG: no USB-serial port matching $WANT -- grant the SOM carrier's console (the USB-UART bridge on its miniUSB) to this machine" >&2
        all=$(ports)
        [ -n "$all" ] && { echo "$PROG: ports present:" >&2; printf '%s\n' "$all" | sed 's/^/  /' >&2; }
        exit 1
    fi
    if [ "$n" -gt 1 ]; then
        echo "$PROG: $n ports match $WANT -- name one with --serial or --dev:" >&2
        matching | sed 's/^/  /' >&2
        exit 1
    fi
    dev="$DEVDIR/$hits"
fi

if [ "$mode" = find ]; then
    echo "$dev"
    exit 0
fi

[ -c "$dev" ] || { echo "$PROG: $dev is not a character device" >&2; exit 1; }
command -v picocom >/dev/null 2>&1 || { echo "$PROG: picocom is not installed" >&2; exit 1; }
echo "$PROG: $dev at $BAUD 8N1 -- C-a C-x leaves"
exec picocom -b "$BAUD" "$dev"