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[2/4] USB: serial: io_ti: document reason for drain delay

Message ID 20210412093815.736-3-johan@kernel.org (mailing list archive)
State Accepted
Commit 4b8e07951ff53e702bd5d6d21450b17152d124d7
Headers show
Series USB: serial: closing-wait fixes and cleanups | expand

Commit Message

Johan Hovold April 12, 2021, 9:38 a.m. UTC 
Document that the device line-status register doesn't tell when the
transmitter shift register has emptied and that this is why the
one-character drain delay is needed.

Signed-off-by: Johan Hovold <johan@kernel.org>
---
 drivers/usb/serial/io_ti.c | 4 ++++
 1 file changed, 4 insertions(+)
diff mbox series

Patch

diff --git a/drivers/usb/serial/io_ti.c b/drivers/usb/serial/io_ti.c
index 75325c2b295e..17720670e06c 100644
--- a/drivers/usb/serial/io_ti.c
+++ b/drivers/usb/serial/io_ti.c
@@ -2590,6 +2590,10 @@  static int edge_port_probe(struct usb_serial_port *port)
 	if (ret)
 		goto err;
 
+	/*
+	 * The LSR does not tell when the transmitter shift register has
+	 * emptied so add a one-character drain delay.
+	 */
 	port->port.drain_delay = 1;
 
 	return 0;