Despite of the existing patch (e.g. https://github.com/tiggerite/mint-17.3-for-surface-pro-3/blob/master/patches-4.3/surface-cam.patch), it seems some surface pro 4 model (E.g. my i7 16G) uses a different webcam solution.
From windows, there are three camera listed with "Camera" in their driver name.
They are Microsoft Camera Front, Microsoft Camera Rear and Microsoft IR Camera Front.
The properties dialogs show that they are OV5693, OV7251 and OV8865, seems they are i2c device instead of usb device.
Seems like the driver was moved into staging