[PATCH 1/6] USB: serial: digi_acceleport: reduce chars_in_buffer over-reporting

From: Johan Hovold
Date: Wed May 19 2021 - 05:20:49 EST


Due to an ancient quirk in n_tty poll implementation, the
digi_acceleport driver has been reporting that its queue contains 256
(WAKEUP_CHARS) characters whenever its write URB is in use.

This has not been necessary since 2003 when the line-discipline started
taking the write room into account so let's return the maximum transfer
size again in order to over-report a little less and incidentally fix
the related debug statement.

Signed-off-by: Johan Hovold <johan@xxxxxxxxxx>
---
drivers/usb/serial/digi_acceleport.c | 3 +--
1 file changed, 1 insertion(+), 2 deletions(-)

diff --git a/drivers/usb/serial/digi_acceleport.c b/drivers/usb/serial/digi_acceleport.c
index 19ee8191647c..a4194b70a6fe 100644
--- a/drivers/usb/serial/digi_acceleport.c
+++ b/drivers/usb/serial/digi_acceleport.c
@@ -1048,8 +1048,7 @@ static unsigned int digi_chars_in_buffer(struct tty_struct *tty)
if (priv->dp_write_urb_in_use) {
dev_dbg(&port->dev, "digi_chars_in_buffer: port=%d, chars=%d\n",
priv->dp_port_num, port->bulk_out_size - 2);
- /* return(port->bulk_out_size - 2); */
- return 256;
+ return port->bulk_out_size - 2;
} else {
dev_dbg(&port->dev, "digi_chars_in_buffer: port=%d, chars=%d\n",
priv->dp_port_num, priv->dp_out_buf_len);
--
2.26.3