umbim: introduce devpath option

Introduce the devpath option to find the control channel device from a
hardware path for a USB or a WWAN device.

This option is useful when there are multiple modems connected to the
system. The name of the control channel device of a modem can change
depending on which modem initialises first or if it was recently plugged
in. The devpath option allows specifying the hardware path of the modem
where the control channel device will be found using that.

For the USB device hardware path, it is allowed to specify the USB port
number the modem is directly connected to.

If the device and devpath options are both set, devpath takes precedence
over device.

The USB device hardware path of a control channel device can be found by:

readlink -f /sys/class/usbmisc/cdc-wdmX/device

The WWAN device hardware path of a control channel device can be found by:

readlink -f /sys/class/wwan/wwanXmbimX/device

An example uci configuration would be:

config interface 'wwan_usb1'
	option proto 'mbim'
	option auth 'none'
	option devpath '/sys/devices/platform/1e1c0000.xhci/usb1/1-1'
	option apn 'internet'
	option pdptype 'ipv4v6'

Or:

config interface 'wwan_pcie1'
	option proto 'mbim'
	option auth 'none'
	option devpath '/sys/devices/platform/soc/11280000.pcie/pci0003:00/0003:00:00.0/0003:01:00.0'
	option apn 'internet'
	option pdptype 'ipv4v6'

Signed-off-by: Chester A. Unal <chester.a.unal@arinc9.com>

Author: arinc9

package/network/utils/umbim/files/lib/netifd/proto/mbim.sh

@@ -20,6 +20,7 @@ proto_mbim_init_config() {
 	proto_config_add_string username
 	proto_config_add_string password
 	[ -e /proc/sys/net/ipv6 ] && proto_config_add_string ipv6
+	proto_config_add_string devpath
 	proto_config_add_string dhcp
 	proto_config_add_string dhcpv6
 	proto_config_add_boolean sourcefilter
@@ -46,8 +47,8 @@ _proto_mbim_setup() {
 	local tid=2
 	local ret
 
-	local allow_partner allow_roaming apn auth delay device password pincode username
-	json_get_vars allow_partner allow_roaming apn auth delay device password pincode username
+	local allow_partner allow_roaming apn auth delay device devpath password pincode username
+	json_get_vars allow_partner allow_roaming apn auth delay device devpath password pincode username
 
 	local dhcp dhcpv6 pdptype
 	json_get_vars dhcp dhcpv6 pdptype
@@ -59,6 +60,30 @@ _proto_mbim_setup() {
 
 	[ -n "$ctl_device" ] && device=$ctl_device
 
+	if [ -n "$devpath" ]; then
+		local usbmisc_or_wwan_path
+		# For usbmisc:
+		# /sys/devices/platform/1e1c0000.xhci/usb1/1-2/1-2:1.4/usbmisc/cdc-wdm0
+		# Numbers after ":" are the configuration and interface number
+		# of the connected modem. There can be multiple interfaces but
+		# there will only be a single interface that provides the
+		# control channel device. Therefore, check also /*/usbmisc to
+		# allow specifying the USB port number the modem is directly
+		# connected to.
+		# For wwan:
+		# /sys/devices/platform/soc/11280000.pcie/pci0003:00/0003:00:00.0/0003:01:00.0/wwan/wwan0/wwan0mbim0
+		# /sys/devices/platform/soc/11280000.pcie/pci0003:00/0003:00:00.0/0003:01:00.0/mhi0/wwan/wwan0/wwan0mbim0
+		for usbmisc_or_wwan_path in \
+		    "$devpath"/usbmisc/cdc-wdm* \
+		    "$devpath"/*/usbmisc/cdc-wdm* \
+		    "$devpath"/*/wwan[0-9]*/wwan[0-9]*mbim* \
+		    "$devpath"/*/*/wwan[0-9]*/wwan[0-9]*mbim*; do
+			[ ! -e "$usbmisc_or_wwan_path" ] && continue
+			device="/dev/${usbmisc_or_wwan_path##*/}"
+			break
+		done
+	fi
+
 	[ -n "$device" ] || {
 		echo "mbim[$$]" "No control device specified"
 		proto_notify_error "$interface" NO_DEVICE
@@ -321,12 +346,23 @@ proto_mbim_setup() {
 proto_mbim_teardown() {
 	local interface="$1"
 
-	local device
-	json_get_vars device
+	local device devpath
+	json_get_vars device devpath
 	local tid=$(uci_get_state network $interface tid)
 
 	[ -n "$ctl_device" ] && device=$ctl_device
 
+	if [ -n "$devpath" ]; then
+		local usbmisc_or_wwan_path
+		for usbmisc_or_wwan_path in \
+		    "$devpath"/usbmisc/cdc-wdm* \
+		    "$devpath"/*/usbmisc/cdc-wdm* \
+		    "$devpath"/*/wwan[0-9]*/wwan[0-9]*mbim* \
+		    "$devpath"/*/*/wwan[0-9]*/wwan[0-9]*mbim*; do
+			device="/dev/${usbmisc_or_wwan_path##*/}"
+		done
+	fi
+
 	echo "mbim[$$]" "Stopping network"
 	[ -n "$tid" ] && {
 		umbim $DBG -t $tid -d "$device" disconnect