Quote:
Originally Posted by
SDoroshenko
All the USB modem drivers I test (cdc-acm, option, sierra) send data to modems by using usb_submit_urb call.
Of course they do. Data for USB modems gets sent over USB. The modem must have a way to inform the Linux kernel when to send data or when not to send data but this depends on the hardware.
Quote:
The facts Linux provides flow control without packet loss and sendto call blocks itself if modem buffer is full mean Linux can check if modem buffer is full
Not necessarily. For some hardware it might be the other way around -- the
modem might tell
Linux when the buffer is full or not full.
How it works depends on the hardware.