treewide, serdev: change receive_buf() return type to size_t

receive_buf() is called from ttyport_receive_buf() that expects values
">= 0" from serdev_controller_receive_buf(), change its return type from
ssize_t to size_t.

The need for this clean-up was noticed while fixing a warning, see
commit 94d0539425 ("Bluetooth: btnxpuart: fix recv_buf() return value").
Changing the callback prototype to return an unsigned seems the best way
to document the API and ensure that is properly used.

GNSS drivers implementation of serdev receive_buf() callback return
directly the return value of gnss_insert_raw(). gnss_insert_raw()
returns a signed int, however this is not an issue since the value
returned is always positive, because of the kfifo_in() implementation.
gnss_insert_raw() could be changed to return also an unsigned, however
this is not implemented here as request by the GNSS maintainer Johan
Hovold.

Suggested-by: Jiri Slaby <jirislaby@kernel.org>
Link: https://lore.kernel.org/all/087be419-ec6b-47ad-851a-5e1e3ea5cfcc@kernel.org/
Signed-off-by: Francesco Dolcini <francesco.dolcini@toradex.com>
Acked-by: Jonathan Cameron <Jonathan.Cameron@huawei.com> #for-iio
Reviewed-by: Johan Hovold <johan@kernel.org>
Reviewed-by: Rob Herring <robh@kernel.org>
Reviewed-by: Alex Elder <elder@linaro.org>
Acked-by: Maximilian Luz <luzmaximilian@gmail.com>  # for platform/surface
Acked-by: Lee Jones <lee@kernel.org>
Acked-by: Ilpo Järvinen <ilpo.jarvinen@linux.intel.com>
Link: https://lore.kernel.org/r/20240122180551.34429-1-francesco@dolcini.it
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

drivers/bluetooth/btmtkuart.c

@@ -383,8 +383,8 @@ static void btmtkuart_recv(struct hci_dev *hdev, const u8 *data, size_t count)
 	}
 }
 
-static ssize_t btmtkuart_receive_buf(struct serdev_device *serdev,
-				     const u8 *data, size_t count)
+static size_t btmtkuart_receive_buf(struct serdev_device *serdev,
+				    const u8 *data, size_t count)
 {
 	struct btmtkuart_dev *bdev = serdev_device_get_drvdata(serdev);
 

drivers/bluetooth/btnxpuart.c

@@ -1264,8 +1264,8 @@ static const struct h4_recv_pkt nxp_recv_pkts[] = {
 	{ NXP_RECV_FW_REQ_V3,   .recv = nxp_recv_fw_req_v3 },
 };
 
-static ssize_t btnxpuart_receive_buf(struct serdev_device *serdev,
-				     const u8 *data, size_t count)
+static size_t btnxpuart_receive_buf(struct serdev_device *serdev,
+				    const u8 *data, size_t count)
 {
 	struct btnxpuart_dev *nxpdev = serdev_device_get_drvdata(serdev);
 

drivers/bluetooth/hci_serdev.c

@@ -271,8 +271,8 @@ static void hci_uart_write_wakeup(struct serdev_device *serdev)
  *
  * Return: number of processed bytes
  */
-static ssize_t hci_uart_receive_buf(struct serdev_device *serdev,
-				    const u8 *data, size_t count)
+static size_t hci_uart_receive_buf(struct serdev_device *serdev,
+				   const u8 *data, size_t count)
 {
 	struct hci_uart *hu = serdev_device_get_drvdata(serdev);
 

drivers/gnss/serial.c

@@ -80,7 +80,7 @@ static const struct gnss_operations gnss_serial_gnss_ops = {
 	.write_raw	= gnss_serial_write_raw,
 };
 
-static ssize_t gnss_serial_receive_buf(struct serdev_device *serdev,
+static size_t gnss_serial_receive_buf(struct serdev_device *serdev,
 				       const u8 *buf, size_t count)
 {
 	struct gnss_serial *gserial = serdev_device_get_drvdata(serdev);

drivers/gnss/sirf.c

@@ -160,7 +160,7 @@ static const struct gnss_operations sirf_gnss_ops = {
 	.write_raw	= sirf_write_raw,
 };
 
-static ssize_t sirf_receive_buf(struct serdev_device *serdev,
+static size_t sirf_receive_buf(struct serdev_device *serdev,
 				const u8 *buf, size_t count)
 {
 	struct sirf_data *data = serdev_device_get_drvdata(serdev);

drivers/greybus/gb-beagleplay.c

@@ -271,7 +271,7 @@ static void hdlc_rx_frame(struct gb_beagleplay *bg)
 	}
 }
 
-static ssize_t hdlc_rx(struct gb_beagleplay *bg, const u8 *data, size_t count)
+static size_t hdlc_rx(struct gb_beagleplay *bg, const u8 *data, size_t count)
 {
 	size_t i;
 	u8 c;
@@ -331,8 +331,8 @@ static void hdlc_deinit(struct gb_beagleplay *bg)
 	flush_work(&bg->tx_work);
 }
 
-static ssize_t gb_tty_receive(struct serdev_device *sd, const u8 *data,
-			      size_t count)
+static size_t gb_tty_receive(struct serdev_device *sd, const u8 *data,
+			     size_t count)
 {
 	struct gb_beagleplay *bg = serdev_device_get_drvdata(sd);
 

drivers/iio/chemical/pms7003.c

@@ -211,8 +211,8 @@ static bool pms7003_frame_is_okay(struct pms7003_frame *frame)
 	return checksum == pms7003_calc_checksum(frame);
 }
 
-static ssize_t pms7003_receive_buf(struct serdev_device *serdev, const u8 *buf,
-				   size_t size)
+static size_t pms7003_receive_buf(struct serdev_device *serdev, const u8 *buf,
+				  size_t size)
 {
 	struct iio_dev *indio_dev = serdev_device_get_drvdata(serdev);
 	struct pms7003_state *state = iio_priv(indio_dev);

drivers/iio/chemical/scd30_serial.c

@@ -174,8 +174,8 @@ static int scd30_serdev_command(struct scd30_state *state, enum scd30_cmd cmd, u
 	return 0;
 }
 
-static ssize_t scd30_serdev_receive_buf(struct serdev_device *serdev,
-					const u8 *buf, size_t size)
+static size_t scd30_serdev_receive_buf(struct serdev_device *serdev,
+				       const u8 *buf, size_t size)
 {
 	struct iio_dev *indio_dev = serdev_device_get_drvdata(serdev);
 	struct scd30_serdev_priv *priv;

drivers/iio/chemical/sps30_serial.c

@@ -210,8 +210,8 @@ static int sps30_serial_command(struct sps30_state *state, unsigned char cmd,
 	return rsp_size;
 }
 
-static ssize_t sps30_serial_receive_buf(struct serdev_device *serdev,
-					const u8 *buf, size_t size)
+static size_t sps30_serial_receive_buf(struct serdev_device *serdev,
+				       const u8 *buf, size_t size)
 {
 	struct iio_dev *indio_dev = dev_get_drvdata(&serdev->dev);
 	struct sps30_serial_priv *priv;

drivers/iio/imu/bno055/bno055_ser_core.c

@@ -378,8 +378,8 @@ static void bno055_ser_handle_rx(struct bno055_ser_priv *priv, int status)
  * Also, we assume to RX one pkt per time (i.e. the HW doesn't send anything
  * unless we require to AND we don't queue more than one request per time).
  */
-static ssize_t bno055_ser_receive_buf(struct serdev_device *serdev,
-				      const u8 *buf, size_t size)
+static size_t bno055_ser_receive_buf(struct serdev_device *serdev,
+				     const u8 *buf, size_t size)
 {
 	int status;
 	struct bno055_ser_priv *priv = serdev_device_get_drvdata(serdev);

drivers/mfd/rave-sp.c

@@ -471,8 +471,8 @@ static void rave_sp_receive_frame(struct rave_sp *sp,
 		rave_sp_receive_reply(sp, data, length);
 }
 
-static ssize_t rave_sp_receive_buf(struct serdev_device *serdev,
-				   const u8 *buf, size_t size)
+static size_t rave_sp_receive_buf(struct serdev_device *serdev,
+				  const u8 *buf, size_t size)
 {
 	struct device *dev = &serdev->dev;
 	struct rave_sp *sp = dev_get_drvdata(dev);

drivers/net/ethernet/qualcomm/qca_uart.c

@@ -58,7 +58,7 @@ struct qcauart {
 	unsigned char *tx_buffer;
 };
 
-static ssize_t
+static size_t
 qca_tty_receive(struct serdev_device *serdev, const u8 *data, size_t count)
 {
 	struct qcauart *qca = serdev_device_get_drvdata(serdev);

drivers/nfc/pn533/uart.c

@@ -203,8 +203,8 @@ static int pn532_uart_rx_is_frame(struct sk_buff *skb)
 	return 0;
 }
 
-static ssize_t pn532_receive_buf(struct serdev_device *serdev,
-				 const u8 *data, size_t count)
+static size_t pn532_receive_buf(struct serdev_device *serdev,
+				const u8 *data, size_t count)
 {
 	struct pn532_uart_phy *dev = serdev_device_get_drvdata(serdev);
 	size_t i;

drivers/nfc/s3fwrn5/uart.c

@@ -51,8 +51,8 @@ static const struct s3fwrn5_phy_ops uart_phy_ops = {
 	.write = s3fwrn82_uart_write,
 };
 
-static ssize_t s3fwrn82_uart_read(struct serdev_device *serdev,
-				  const u8 *data, size_t count)
+static size_t s3fwrn82_uart_read(struct serdev_device *serdev,
+				 const u8 *data, size_t count)
 {
 	struct s3fwrn82_uart_phy *phy = serdev_device_get_drvdata(serdev);
 	size_t i;

drivers/platform/chrome/cros_ec_uart.c

@@ -81,8 +81,8 @@ struct cros_ec_uart {
 	struct response_info response;
 };
 
-static ssize_t cros_ec_uart_rx_bytes(struct serdev_device *serdev,
-				     const u8 *data, size_t count)
+static size_t cros_ec_uart_rx_bytes(struct serdev_device *serdev,
+				    const u8 *data, size_t count)
 {
 	struct ec_host_response *host_response;
 	struct cros_ec_device *ec_dev = serdev_device_get_drvdata(serdev);

drivers/platform/surface/aggregator/core.c

@@ -227,8 +227,8 @@ EXPORT_SYMBOL_GPL(ssam_client_bind);
 
 /* -- Glue layer (serdev_device -> ssam_controller). ------------------------ */
 
-static ssize_t ssam_receive_buf(struct serdev_device *dev, const u8 *buf,
-				size_t n)
+static size_t ssam_receive_buf(struct serdev_device *dev, const u8 *buf,
+			       size_t n)
 {
 	struct ssam_controller *ctrl;
 	int ret;

drivers/tty/serdev/serdev-ttyport.c

@@ -27,19 +27,17 @@ static size_t ttyport_receive_buf(struct tty_port *port, const u8 *cp,
 {
 	struct serdev_controller *ctrl = port->client_data;
 	struct serport *serport = serdev_controller_get_drvdata(ctrl);
-	int ret;
+	size_t ret;
 
 	if (!test_bit(SERPORT_ACTIVE, &serport->flags))
 		return 0;
 
 	ret = serdev_controller_receive_buf(ctrl, cp, count);
 
-	dev_WARN_ONCE(&ctrl->dev, ret < 0 || ret > count,
-				"receive_buf returns %d (count = %zu)\n",
+	dev_WARN_ONCE(&ctrl->dev, ret > count,
+				"receive_buf returns %zu (count = %zu)\n",
 				ret, count);
-	if (ret < 0)
-		return 0;
-	else if (ret > count)
+	if (ret > count)
 		return count;
 
 	return ret;

include/linux/serdev.h

@@ -27,7 +27,7 @@ struct serdev_device;
  *			not sleep.
  */
 struct serdev_device_ops {
-	ssize_t (*receive_buf)(struct serdev_device *, const u8 *, size_t);
+	size_t (*receive_buf)(struct serdev_device *, const u8 *, size_t);
 	void (*write_wakeup)(struct serdev_device *);
 };
 
@@ -185,9 +185,9 @@ static inline void serdev_controller_write_wakeup(struct serdev_controller *ctrl
 	serdev->ops->write_wakeup(serdev);
 }
 
-static inline ssize_t serdev_controller_receive_buf(struct serdev_controller *ctrl,
-						    const u8 *data,
-						    size_t count)
+static inline size_t serdev_controller_receive_buf(struct serdev_controller *ctrl,
+						   const u8 *data,
+						   size_t count)
 {
 	struct serdev_device *serdev = ctrl->serdev;
 

sound/drivers/serial-generic.c

@@ -100,8 +100,8 @@ static void snd_serial_generic_write_wakeup(struct serdev_device *serdev)
 	snd_serial_generic_tx_wakeup(drvdata);
 }
 
-static ssize_t snd_serial_generic_receive_buf(struct serdev_device *serdev,
-					      const u8 *buf, size_t count)
+static size_t snd_serial_generic_receive_buf(struct serdev_device *serdev,
+					     const u8 *buf, size_t count)
 {
 	int ret;
 	struct snd_serial_generic *drvdata = serdev_device_get_drvdata(serdev);