c23e5fc1f7
Remove multi-urb write from the generic driver and simplify the prepare_write_buffer prototype: int (*prepare_write_buffer)(struct usb_serial_port *port, void *dest, size_t size); The default implementation simply fills dest with data from port write fifo but drivers can override it if they need to process the outgoing data (e.g. add headers). Turn ftdi_sio into a generic fifo-based driver, which lowers CPU usage significantly for small writes while retaining maximum throughput. Signed-off-by: Johan Hovold <jhovold@gmail.com> Signed-off-by: Greg Kroah-Hartman <gregkh@suse.de>