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usb: gadget: serial: fix Tx stall after buffer overflow 

[ Upstream commit e4bfded56c ]

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.

Signed-off-by: Sergey Organov <sorganov@gmail.com>
Reviewed-by: Michał Mirosław <mirq-linux@rere.qmqm.pl>
Signed-off-by: Felipe Balbi <balbi@kernel.org>
Signed-off-by: Sasha Levin <sashal@kernel.org>
5.4-rM2-2.2.x-imx-squashed
Sergey Organov 2020-01-29 14:21:46 +03:00 committed by Greg Kroah-Hartman
parent a3a7d31645
commit 5d48ee3211
1 changed files with 3 additions and 1 deletions
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4
drivers/usb/gadget/function/u_serial.c
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@ -560,8 +560,10 @@ 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() */
tty_wakeup(port->port.tty);
} else {
gs_free_requests(ep, head, &port->read_allocated);