linux-kernel - [PATCH 1/6] USB: serial: digi_acceleport: reduce chars_in

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Date:   Wed, 19 May 2021 11:20:01 +0200
From:   Johan Hovold <johan@...nel.org>
To:     Johan Hovold <johan@...nel.org>
Cc:     Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        Jiri Slaby <jirislaby@...nel.org>, linux-usb@...r.kernel.org,
        linux-kernel@...r.kernel.org
Subject: [PATCH 1/6] USB: serial: digi_acceleport: reduce chars_in_buffer over-reporting

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@...nel.org>
---
 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