Function schedule_transfer

src/phys/usb.rs:412–468

(ep: u32, tx: bool, transfer: &mut UsbEndpointTransferDescriptor)

}

fn schedule_transfer(ep: u32, tx: bool, transfer: &mut UsbEndpointTransferDescriptor) {
    let qh = usb_get_queuehead(ep as usize, tx);
    let mask = match tx {
        true => 1 << (ep + 16),
        false => 1 << ep,
    };

    loop {
        // Case 2. The queue is not empty.
        if qh.last_transfer > 1 {
            let last = qh.get_last_transfer();

            // Add the new dtd to the end of the queue
            last.next = (transfer as *const UsbEndpointTransferDescriptor) as u32;

            // If the thing is still primed, hooray we're done.
            if (read_word(ENDPTPRIME) & mask) > 0 {
                break;
            }

            let mut status;
            loop {
                // Set ATDTW bit to USBCMD
                assign(USBCMD, read_word(USBCMD) | (1 << 14));
                // Read status for current queue
                status = read_word(ENDPTSTAT) & mask;
                // Read atdtw bit
                let atdtw = read_word(USBCMD) & (1 << 14);
                // If it's zero, restart this process.
                // If it's one, we can continue.
                if atdtw > 0 {
                    break;
                } else {
                    assembly!("nop");
                }
            }

            // Write atdtw as zero
            assign(USBCMD, read_word(USBCMD) & !(1 << 14));

            // If status bit is set, we're done. Otherwise, fall into Case 1.
            if status > 0 {
                break;
            }
        }

        // Case 1. The queue is empty
        qh.next = (transfer as *const UsbEndpointTransferDescriptor) as u32;
        qh.status = 0;

        usb_prime_endpoint(ep, tx);
        qh.set_first_transfer(transfer);
        break;
    }

    qh.set_last_transfer(transfer);
}