On 2/24/21 12:04 PM, Johan Hovold wrote:

Perhaps you can even figure out how to poll for an empty TX FIFO from
it, unless Charles is able to provide some details on that separate
matter?

I presume from the code below, that when the device is closed, all data waiting to send is clobbered (if so, so the problem is the driver and not the device)

I would have thought that the driver should drain the buffers. I can see that this might be a problem if there is flow control (it may never drain) but the current method seems pretty brutal.


119 void usb_serial_generic_close(struct usb_serial_port *port)
120 {
121         unsigned long flags;
122         int i;
123
124         if (port->bulk_out_size) {
125                 for (i = 0; i < ARRAY_SIZE(port->write_urbs); ++i)
126                         usb_kill_urb(port->write_urbs[i]);
127
128                 spin_lock_irqsave(&port->lock, flags);
129                 kfifo_reset_out(&port->write_fifo);
130                 spin_unlock_irqrestore(&port->lock, flags);
131         }
132         if (port->bulk_in_size) {
133                 for (i = 0; i < ARRAY_SIZE(port->read_urbs); ++i)
134                         usb_kill_urb(port->read_urbs[i]);
135         }
136 }