linux kernel support console on usb gadget serial port (ttyGSX)

kernel config example (rpi0):

CONFIG_USB_OTG=y
CONFIG_USB_DWC2=y
CONFIG_USB_DWC2_PERIPHERAL=y # default use gadget mode
CONFIG_USB_GADGET=y
CONFIG_USB_G_SERIAL=y # compile gadget serial in kernel
CONFIG_U_SERIAL_CONSOLE=y # allow console use usb gadget serial port

then append kernel argument:

console=ttyGS0,115200

you may be need change devicetree to enable dwc2

config.txt:

dtoverlay=dwc2

then bootup board.

you will get a serial port device ’/dev/ttyACMX’ on your computer:

dmesg:

usb 3-1: USB disconnect, device number 7
usb 3-1: new high-speed USB device number 8 using xhci_hcd
usb 3-1: New USB device found, idVendor=0525, idProduct=a4a7, bcdDevice= 5.10
usb 3-1: New USB device strings: Mfr=1, Product=2, SerialNumber=0
usb 3-1: Product: Gadget Serial v2.4
usb 3-1: Manufacturer: Linux 5.10.92 with 20980000.usb
cdc_acm 3-1:2.0: ttyACM0: USB ACM device
usbcore: registered new interface driver cdc_acm
cdc_acm: USB Abstract Control Model driver for USB modems and ISDN adapters

connect it, you will see kernel boot log.

you can also run ’getty’ on serial port.

many GNU/Linux on android phone use this method.

kernel config example (rpi0):

TODO