linux-kernel - [PATCH v2 4/6] USB: serial: ftdi_sio: use usb_control_msg

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Date:   Mon,  2 Aug 2021 02:01:20 +0530
From:   Himadri Pandya <himadrispandya@...il.com>
To:     johan@...nel.org, gregkh@...uxfoundation.org,
        linux-usb@...r.kernel.org, linux-kernel@...r.kernel.org
Cc:     Himadri Pandya <himadrispandya@...il.com>
Subject: [PATCH v2 4/6] USB: serial: ftdi_sio: use usb_control_msg_recv()

usb_control_msg_recv() nicely wraps usb_control_msg() and removes the
compulsion of using dma buffers for usb messages. It also includes proper
error check for possible short read. So use the wrapper and remove dma
buffers from the callers.

Signed-off-by: Himadri Pandya <himadrispandya@...il.com>
---
Changes in v2:
 - Drop unnecessary use of wrappers
---
 drivers/usb/serial/ftdi_sio.c | 53 ++++++++++-------------------------
 1 file changed, 15 insertions(+), 38 deletions(-)

diff --git a/drivers/usb/serial/ftdi_sio.c b/drivers/usb/serial/ftdi_sio.c
index 4a1f3a95d017..d4c61568b549 100644
--- a/drivers/usb/serial/ftdi_sio.c
+++ b/drivers/usb/serial/ftdi_sio.c
@@ -1436,27 +1436,15 @@ static int _read_latency_timer(struct usb_serial_port *port)
 {
 	struct ftdi_private *priv = usb_get_serial_port_data(port);
 	struct usb_device *udev = port->serial->dev;
-	unsigned char *buf;
+	u8 buf;
 	int rv;
 
-	buf = kmalloc(1, GFP_KERNEL);
-	if (!buf)
-		return -ENOMEM;
-
-	rv = usb_control_msg(udev,
-			     usb_rcvctrlpipe(udev, 0),
-			     FTDI_SIO_GET_LATENCY_TIMER_REQUEST,
-			     FTDI_SIO_GET_LATENCY_TIMER_REQUEST_TYPE,
-			     0, priv->interface,
-			     buf, 1, WDR_TIMEOUT);
-	if (rv < 1) {
-		if (rv >= 0)
-			rv = -EIO;
-	} else {
-		rv = buf[0];
-	}
-
-	kfree(buf);
+	rv = usb_control_msg_recv(udev, 0, FTDI_SIO_GET_LATENCY_TIMER_REQUEST,
+				  FTDI_SIO_GET_LATENCY_TIMER_REQUEST_TYPE, 0,
+				  priv->interface, &buf, 1, WDR_TIMEOUT,
+				  GFP_KERNEL);
+	if (rv == 0)
+		rv = buf;
 
 	return rv;
 }
@@ -1851,32 +1839,21 @@ static int ftdi_read_cbus_pins(struct usb_serial_port *port)
 {
 	struct ftdi_private *priv = usb_get_serial_port_data(port);
 	struct usb_serial *serial = port->serial;
-	unsigned char *buf;
+	u8 buf;
 	int result;
 
 	result = usb_autopm_get_interface(serial->interface);
 	if (result)
 		return result;
 
-	buf = kmalloc(1, GFP_KERNEL);
-	if (!buf) {
-		usb_autopm_put_interface(serial->interface);
-		return -ENOMEM;
-	}
-
-	result = usb_control_msg(serial->dev,
-				 usb_rcvctrlpipe(serial->dev, 0),
-				 FTDI_SIO_READ_PINS_REQUEST,
-				 FTDI_SIO_READ_PINS_REQUEST_TYPE, 0,
-				 priv->interface, buf, 1, WDR_TIMEOUT);
-	if (result < 1) {
-		if (result >= 0)
-			result = -EIO;
-	} else {
-		result = buf[0];
-	}
+	result = usb_control_msg_recv(serial->dev, 0,
+				      FTDI_SIO_READ_PINS_REQUEST,
+				      FTDI_SIO_READ_PINS_REQUEST_TYPE, 0,
+				      priv->interface, &buf, 1, WDR_TIMEOUT,
+				      GFP_KERNEL);
+	if (result == 0)
+		result = buf;
 
-	kfree(buf);
 	usb_autopm_put_interface(serial->interface);
 
 	return result;
-- 
2.17.1