openipc-builder/devices/gk7205v200_otg_generic/general/overlay/usr/bin/usb-mode

#!/bin/sh
#
# Switch the single DWC3 controller between USB host and USB device roles.
#
# host   - xHCI drives the port. This is what the usbcam second-camera path
#          needs (majestic consuming a USB webcam).
# device - the UVC gadget drives the port, so a PC sees this camera as a
#          webcam.
#
# The two are mutually exclusive: xHCI HCSPARAMS1 reports MaxPorts = 1, so
# there is one port and one role at a time. Switching does not need a reboot.
#
# Why this is more than one echo: dwc3_set_mode() (drivers/usb/dwc3/core.c)
# only flips GCTL.PRTCAPDIR. It does not stop the host stack or start the
# gadget stack. Writing the debugfs `mode` file on its own leaves xHCI still
# bound and its DMA engine still live, pointed at a controller that has been
# re-aimed underneath it. Unbind first, then flip, then bring the other side
# up.

set -e

STATE=/etc/usbmode
GADGET=/sys/kernel/config/usb_gadget/uvc0

die() { echo "usb-mode: $*" >&2; exit 1; }

dwc3_mode_file() {
	for f in /sys/kernel/debug/*.dwc3/mode; do
		[ -e "$f" ] && { echo "$f"; return 0; }
	done
	return 1
}

xhci_device() {
	for d in /sys/bus/platform/drivers/xhci-hcd/*.auto; do
		[ -e "$d" ] && { basename "$d"; return 0; }
	done
	# Not currently bound; fall back to the device that exists on the bus.
	for d in /sys/bus/platform/devices/xhci-hcd.*.auto; do
		[ -e "$d" ] && { basename "$d"; return 0; }
	done
	return 1
}

udc_name() {
	for u in /sys/class/udc/*; do
		[ -e "$u" ] && { basename "$u"; return 0; }
	done
	return 1
}

need_debugfs() {
	mountpoint -q /sys/kernel/debug 2>/dev/null ||
		mount -t debugfs none /sys/kernel/debug
	MODE_FILE=$(dwc3_mode_file) ||
		die "no dwc3 mode file; is CONFIG_USB_DWC3_DUAL_ROLE enabled and debugfs mounted?"
}

teardown_gadget() {
	[ -d "$GADGET" ] || return 0

	# Unbind from the UDC first: this drops the D+ pullup so the host sees a
	# disconnect rather than a device that stops answering.
	if [ -e "$GADGET/UDC" ] && [ -s "$GADGET/UDC" ]; then
		echo "" > "$GADGET/UDC" 2>/dev/null || true
	fi

	# configfs rmdir is strict about ordering: links before the things they
	# point at, leaves before their parents. ENOTEMPTY here means something
	# below was missed.
	rm -f "$GADGET/configs/c.1/uvc.0"

	F="$GADGET/functions/uvc.0"
	rm -f "$F/control/class/fs/h" "$F/control/class/ss/h"
	rm -f "$F/streaming/class/fs/h" "$F/streaming/class/hs/h" "$F/streaming/class/ss/h"
	# uvc-gadget-setup composes whichever single format majestic is set to, so
	# tear down both possibilities: only one of them exists on any given boot.
	rm -f "$F/streaming/header/h/f"
	rmdir "$F/streaming/header/h"      2>/dev/null || true
	rmdir "$F/streaming/mjpeg/m/f"     2>/dev/null || true
	rmdir "$F/streaming/mjpeg/m"       2>/dev/null || true
	rmdir "$F/streaming/framebased/h/f" 2>/dev/null || true
	rmdir "$F/streaming/framebased/h"  2>/dev/null || true
	rmdir "$F/control/header/h"        2>/dev/null || true

	# EBUSY here means a userspace process still holds the gadget's
	# /dev/videoN open -- almost always majestic. Stop it first.
	if ! rmdir "$F" 2>/dev/null; then
		die "cannot remove uvc.0 (EBUSY?) -- is majestic still holding /dev/video*? stop it first"
	fi

	rmdir "$GADGET/configs/c.1/strings/0x409" 2>/dev/null || true
	rmdir "$GADGET/configs/c.1"               2>/dev/null || true
	rmdir "$GADGET/strings/0x409"             2>/dev/null || true
	rmdir "$GADGET"                           2>/dev/null || true
}

to_device() {
	need_debugfs

	if X=$(xhci_device) && [ -e "/sys/bus/platform/drivers/xhci-hcd/$X" ]; then
		# Coming straight from boot the controller is still in its power-on
		# GCTL.PRTCAPDIR = OTG(3) (see the header note: nothing moves it off
		# OTG on its own). xhci-hcd binds and registers both buses on top of
		# that anyway, but it is not actually driving the port -- so unbinding
		# directly from OTG asks xhci_halt() to halt a host that was never
		# really running, and it times out:
		#   xhci-hcd.0.auto: Host not halted after 16000 microseconds.
		#   xhci-hcd.0.auto: Host controller not halted, aborting reset.
		# Leaving the controller un-halted is precisely the live-DMA-engine
		# state this unbind exists to avoid. Flip to host first so the already
		# bound xHCI is genuinely running, and the unbind then halts cleanly.
		# A switch from host is already in that state, so only boot pays for it.
		[ "$(cat "$MODE_FILE")" = host ] || echo host > "$MODE_FILE"

		echo "usb-mode: unbinding host controller $X"
		echo "$X" > /sys/bus/platform/drivers/xhci-hcd/unbind
	fi

	echo device > "$MODE_FILE"

	modprobe configfs     2>/dev/null || true
	modprobe libcomposite 2>/dev/null || true
	modprobe usb_f_uvc    2>/dev/null || true

	mountpoint -q /sys/kernel/config 2>/dev/null ||
		mount -t configfs none /sys/kernel/config

	/usr/bin/uvc-gadget-setup

	UDC=$(udc_name) ||
		die "no UDC registered -- is dr_mode=\"otg\" in the device tree?"
	echo "$UDC" > "$GADGET/UDC"

	echo device > "$STATE"
	echo "usb-mode: device (UVC gadget bound to $UDC)"
}

to_host() {
	need_debugfs

	teardown_gadget

	echo host > "$MODE_FILE"

	if X=$(xhci_device) && [ ! -e "/sys/bus/platform/drivers/xhci-hcd/$X" ]; then
		echo "usb-mode: rebinding host controller $X"
		echo "$X" > /sys/bus/platform/drivers/xhci-hcd/bind
	fi

	echo host > "$STATE"
	echo "usb-mode: host"
}

status() {
	need_debugfs
	echo "dwc3 role : $(cat "$MODE_FILE")"
	echo "persisted : $([ -r "$STATE" ] && cat "$STATE" || echo '(unset, defaults to host)')"
	echo "udc       : $(udc_name || echo '(none)')"
	echo "xhci bound: $(xhci_device >/dev/null 2>&1 && \
		([ -e "/sys/bus/platform/drivers/xhci-hcd/$(xhci_device)" ] && echo yes || echo no) || echo '(no device)')"
	echo "gadget    : $([ -d "$GADGET" ] && echo "composed, UDC='$(cat "$GADGET/UDC" 2>/dev/null)'" || echo 'not composed')"
}

case "$1" in
	device) to_device ;;
	host)   to_host ;;
	status) status ;;
	*)
		echo "Usage: $0 {host|device|status}"
		exit 1
		;;
esac