modprobe g_ether on enable; skip reboot if overlay already active

[XECDesign]

Since config.txt could be modified in advance before the device is started, the gadget could be enabled without requiring a reboot.

When used with rpi-power-hat this speeds things up a lot.

[paulober]

Hi @XECDesign, sounds like a good addition. Thanks for the PR.
I found minor issues.

[paulober]

Suggested change

	if ! cfg_has_overlay; then
	# ensure overlay present once
	sed -i "\|^$OVERLAY_LINE\$|d" "$CFG_FW" 2>/dev/null || true
	sed -i "\|^$OVERLAY_LINE\$|d" "$CFG_LEGACY" 2>/dev/null || true
	printf '%s\n' "$OVERLAY_LINE" >> "$CFG_FW" 2>/dev/null || printf '%s\n' "$OVERLAY_LINE" >> "$CFG_LEGACY"
	if ! overlay_active; then
	NEED_REBOOT=true
	fi
	fi
	if ! cfg_has_overlay; then
	# ensure overlay present once
	sed -i "\|^$OVERLAY_LINE\$|d" "$CFG_FW" 2>/dev/null || true
	sed -i "\|^$OVERLAY_LINE\$|d" "$CFG_LEGACY" 2>/dev/null || true
	printf '%s\n' "$OVERLAY_LINE" >> "$CFG_FW" 2>/dev/null || printf '%s\n' "$OVERLAY_LINE" >> "$CFG_LEGACY"
	fi
	if ! overlay_active; then
	NEED_REBOOT=true
	fi

If the module is already in the config but the Pi didn't restart yet the overlay_active will be false but since the check is in the conditional block NEED_REBOOT will not be set.

[paulober]

Suggested change

	overlay_active() { [ -n "$(ls /sys/class/udc/ 2>/dev/null)" ]; }
	overlay_active() { [ "$(ls -A /sys/class/udc 2>/dev/null)" ]; }

If I remember correctly this approach can be prone to shell special features and we might want to go more POSIX compliant here. What do you think?