Missing corresponding source for built-in STP kernel driver (drivers/staging/oculus/stp)

[kismeter]

Hi Meta/Oculus kernel maintainers,

I am trying to locate the complete corresponding source code for a kernel binary distributed with an Oculus/Meta device.
In the extracted boot.img kernel binary, I found the following built-in source path references:

drivers/staging/oculus/stp/stp/common/stp_common.c
drivers/staging/oculus/stp/device/stp_device.c
drivers/staging/oculus/stp/stp/common/stp_pipeline.c
drivers/staging/oculus/stp/stp/controller/stp_controller.c
drivers/staging/oculus/stp/driver/stp_driver.c

The same kernel binary also contains STP-related symbols such as:

stp_channel_open
stp_channel_close
stp_channel_read
stp_channel_write
stp_channel_wait_read_timeout
stp_channel_connected
stp_channel_rx_filled
stp_get_device_ready
stp_protocol_synced
stp_check_stale_channel
register_spi_stp_notifier
unregister_spi_stp_notifier

However, I could not find the corresponding source directory:

drivers/staging/oculus/stp/

in this repository/branch. Under drivers/staging/oculus/, I only see directories such as include, mcu, mfi, oculus_instruction_sampler

Could you please point me to the correct branch/tag/source release that contains the corresponding source code for this built-in STP driver?

I may be looking at the wrong branch, so any guidance on the correct corresponding source release would be appreciated.

Thanks.