On Tue, Mar 10, 2020 at 04:08:35PM +0100, Pavel Machek wrote:
Hi!
From: Sergey Organov sorganov@gmail.com
[ Upstream commit e4bfded56cf39b8d02733c1e6ef546b97961e18a ]
Symptom: application opens /dev/ttyGS0 and starts sending (writing) to it while either USB cable is not connected, or nobody listens on the other side of the cable. If driver circular buffer overflows before connection is established, no data will be written to the USB layer until/unless /dev/ttyGS0 is closed and re-opened again by the application (the latter besides having no means of being notified about the event of establishing of the connection.)
Fix: on open and/or connect, kick Tx to flush circular buffer data to USB layer.
diff --git a/drivers/usb/gadget/function/u_serial.c b/drivers/usb/gadget/function/u_serial.c index d4d317db89df5..38afe96c5cd26 100644 --- a/drivers/usb/gadget/function/u_serial.c +++ b/drivers/usb/gadget/function/u_serial.c @@ -567,8 +567,10 @@ static int gs_start_io(struct gs_port *port) port->n_read = 0; started = gs_start_rx(port);
- /* unblock any pending writes into our circular buffer */ if (started) {
gs_start_tx(port);/* Unblock any pending writes into our circular buffer, in case* we didn't in gs_start_tx() */I'm confused. gs-start_tx() is done twice in a row. Its return convention seem to be 0 in success case, and non-zero on failure. But it is assigned to variable called "started", which does not sound like "error" to me.
Are you sure this is correct?
The function before 'if (started)' is gs_start_rx() - it's RX not TX.
Best Regards, Michał Mirosław