From b286f4e87e325b76789f30337c98ba72e00532e2 Mon Sep 17 00:00:00 2001
From: Tony Lindgren <tony@atomide.com>
Date: Mon, 13 Nov 2023 10:07:52 +0200
Subject: serial: core: Move tty and serdev to be children of serial core port
 device

Let's move tty and serdev controller to be children of the serial core port
device. This way the runtime PM usage count of a child device propagates
to the serial hardware device.

The tty and serdev devices are associated with a specific serial port of
a serial hardware controller device, and we now have serial core hierarchy
of controllers and ports.

The tty device moves happily with just a change of the parent device and
update of device_find_child() handling. The serdev device init needs some
changes to separate the serial hardware controller device from the parent
device.

With this change the tty devices move under sysfs similar to this x86_64
qemu example of a diff of "find /sys -name ttyS*":

 /sys/class/tty/ttyS0
 /sys/class/tty/ttyS3
 /sys/class/tty/ttyS1
-/sys/devices/pnp0/00:04/tty/ttyS0
-/sys/devices/platform/serial8250/tty/ttyS2
-/sys/devices/platform/serial8250/tty/ttyS3
-/sys/devices/platform/serial8250/tty/ttyS1
+/sys/devices/pnp0/00:04/00:04:0/00:04:0.0/tty/ttyS0
+/sys/devices/platform/serial8250/serial8250:0/serial8250:0.3/tty/ttyS3
+/sys/devices/platform/serial8250/serial8250:0/serial8250:0.1/tty/ttyS1
+/sys/devices/platform/serial8250/serial8250:0/serial8250:0.2/tty/ttyS2

If a serdev device is used instead of a tty, it moves in a similar way.

Suggested-by: Johan Hovold <johan@kernel.org>
Cc: Maximilian Luz <luzmaximilian@gmail.com>
Cc: Rob Herring <robh@kernel.org>
Signed-off-by: Tony Lindgren <tony@atomide.com>
Link: https://lore.kernel.org/r/20231113080758.30346-1-tony@atomide.com
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
---
 include/linux/serdev.h | 8 +++++++-
 1 file changed, 7 insertions(+), 1 deletion(-)

(limited to 'include/linux/serdev.h')

diff --git a/include/linux/serdev.h b/include/linux/serdev.h
index f5f97fa25e8a..0ebf53bb254f 100644
--- a/include/linux/serdev.h
+++ b/include/linux/serdev.h
@@ -99,12 +99,14 @@ struct serdev_controller_ops {
 /**
  * struct serdev_controller - interface to the serdev controller
  * @dev:	Driver model representation of the device.
+ * @host:	Serial port hardware controller device
  * @nr:		number identifier for this controller/bus.
  * @serdev:	Pointer to slave device for this controller.
  * @ops:	Controller operations.
  */
 struct serdev_controller {
 	struct device		dev;
+	struct device		*host;
 	unsigned int		nr;
 	struct serdev_device	*serdev;
 	const struct serdev_controller_ops *ops;
@@ -167,7 +169,9 @@ struct serdev_device *serdev_device_alloc(struct serdev_controller *);
 int serdev_device_add(struct serdev_device *);
 void serdev_device_remove(struct serdev_device *);
 
-struct serdev_controller *serdev_controller_alloc(struct device *, size_t);
+struct serdev_controller *serdev_controller_alloc(struct device *host,
+						  struct device *parent,
+						  size_t size);
 int serdev_controller_add(struct serdev_controller *);
 void serdev_controller_remove(struct serdev_controller *);
 
@@ -311,11 +315,13 @@ struct tty_driver;
 
 #ifdef CONFIG_SERIAL_DEV_CTRL_TTYPORT
 struct device *serdev_tty_port_register(struct tty_port *port,
+					struct device *host,
 					struct device *parent,
 					struct tty_driver *drv, int idx);
 int serdev_tty_port_unregister(struct tty_port *port);
 #else
 static inline struct device *serdev_tty_port_register(struct tty_port *port,
+					   struct device *host,
 					   struct device *parent,
 					   struct tty_driver *drv, int idx)
 {
-- 
cgit v1.2.3


From f2470d2bc4327c2c1a604c6e247442dbb14c90c5 Mon Sep 17 00:00:00 2001
From: "Jiri Slaby (SUSE)" <jirislaby@kernel.org>
Date: Wed, 6 Dec 2023 08:37:07 +0100
Subject: tty: serdev: convert to u8 and size_t in serdev_controller_ops

Switch character types to u8 and sizes to size_t. To conform to
characters/sizes in the rest of the tty layer.

In this patch, only struct serdev_controller_ops hooks. The rest will
follow.

Signed-off-by: "Jiri Slaby (SUSE)" <jirislaby@kernel.org>
Cc: Rob Herring <robh@kernel.org>
Link: https://lore.kernel.org/r/20231206073712.17776-23-jirislaby@kernel.org
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
---
 drivers/tty/serdev/serdev-ttyport.c | 2 +-
 include/linux/serdev.h              | 8 ++++----
 2 files changed, 5 insertions(+), 5 deletions(-)

(limited to 'include/linux/serdev.h')

diff --git a/drivers/tty/serdev/serdev-ttyport.c b/drivers/tty/serdev/serdev-ttyport.c
index c5381fe15e1c..e94e090cf0a1 100644
--- a/drivers/tty/serdev/serdev-ttyport.c
+++ b/drivers/tty/serdev/serdev-ttyport.c
@@ -74,7 +74,7 @@ static const struct tty_port_client_operations client_ops = {
  * Callback functions from the serdev core.
  */
 
-static int ttyport_write_buf(struct serdev_controller *ctrl, const unsigned char *data, size_t len)
+static ssize_t ttyport_write_buf(struct serdev_controller *ctrl, const u8 *data, size_t len)
 {
 	struct serport *serport = serdev_controller_get_drvdata(ctrl);
 	struct tty_struct *tty = serport->tty;
diff --git a/include/linux/serdev.h b/include/linux/serdev.h
index 0ebf53bb254f..8cdab2c3b6d5 100644
--- a/include/linux/serdev.h
+++ b/include/linux/serdev.h
@@ -82,7 +82,7 @@ enum serdev_parity {
  * serdev controller structures
  */
 struct serdev_controller_ops {
-	int (*write_buf)(struct serdev_controller *, const unsigned char *, size_t);
+	ssize_t (*write_buf)(struct serdev_controller *, const u8 *, size_t);
 	void (*write_flush)(struct serdev_controller *);
 	int (*write_room)(struct serdev_controller *);
 	int (*open)(struct serdev_controller *);
@@ -185,9 +185,9 @@ static inline void serdev_controller_write_wakeup(struct serdev_controller *ctrl
 	serdev->ops->write_wakeup(serdev);
 }
 
-static inline int serdev_controller_receive_buf(struct serdev_controller *ctrl,
-					      const unsigned char *data,
-					      size_t count)
+static inline ssize_t serdev_controller_receive_buf(struct serdev_controller *ctrl,
+						    const u8 *data,
+						    size_t count)
 {
 	struct serdev_device *serdev = ctrl->serdev;
 
-- 
cgit v1.2.3


From 475fc6e2de6fec0ff3c9a74ddcfd2b52c90adc0d Mon Sep 17 00:00:00 2001
From: "Jiri Slaby (SUSE)" <jirislaby@kernel.org>
Date: Wed, 6 Dec 2023 08:37:08 +0100
Subject: tty: serdev: convert to u8 and size_t

Switch character types to u8 and sizes to size_t. To conform to
characters/sizes in the rest of the tty layer.

This patch converts struct serdev_device_ops hooks and its
instantiations.

Signed-off-by: "Jiri Slaby (SUSE)" <jirislaby@kernel.org>
Cc: Rob Herring <robh@kernel.org>
Acked-by: Johan Hovold <johan@kernel.org>
Link: https://lore.kernel.org/r/20231206073712.17776-24-jirislaby@kernel.org
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
---
 drivers/bluetooth/btmtkuart.c                          |  4 ++--
 drivers/bluetooth/btnxpuart.c                          |  4 ++--
 drivers/bluetooth/hci_serdev.c                         |  4 ++--
 drivers/gnss/serial.c                                  |  4 ++--
 drivers/gnss/sirf.c                                    |  4 ++--
 drivers/greybus/gb-beagleplay.c                        |  5 +++--
 drivers/iio/chemical/pms7003.c                         |  6 +++---
 drivers/iio/chemical/scd30_serial.c                    |  6 +++---
 drivers/iio/chemical/sps30_serial.c                    | 18 +++++++++---------
 drivers/iio/imu/bno055/bno055_ser_core.c               |  6 +++---
 drivers/mfd/rave-sp.c                                  | 10 +++++-----
 drivers/net/ethernet/qualcomm/qca_uart.c               |  5 ++---
 drivers/nfc/pn533/uart.c                               |  4 ++--
 drivers/nfc/s3fwrn5/uart.c                             |  5 ++---
 drivers/platform/chrome/cros_ec_uart.c                 |  5 ++---
 drivers/platform/surface/aggregator/controller.h       |  4 ++--
 drivers/platform/surface/aggregator/core.c             |  4 ++--
 drivers/platform/surface/aggregator/ssh_packet_layer.c |  4 ++--
 drivers/platform/surface/aggregator/ssh_packet_layer.h |  2 +-
 drivers/tty/serdev/core.c                              | 12 +++++-------
 include/linux/serdev.h                                 | 13 +++++++------
 sound/drivers/serial-generic.c                         |  4 ++--
 22 files changed, 65 insertions(+), 68 deletions(-)

(limited to 'include/linux/serdev.h')

diff --git a/drivers/bluetooth/btmtkuart.c b/drivers/bluetooth/btmtkuart.c
index 935feab815d9..d4f4e40ac5d2 100644
--- a/drivers/bluetooth/btmtkuart.c
+++ b/drivers/bluetooth/btmtkuart.c
@@ -385,8 +385,8 @@ static int btmtkuart_recv(struct hci_dev *hdev, const u8 *data, size_t count)
 	return 0;
 }
 
-static int btmtkuart_receive_buf(struct serdev_device *serdev, const u8 *data,
-				 size_t count)
+static ssize_t btmtkuart_receive_buf(struct serdev_device *serdev,
+				     const u8 *data, size_t count)
 {
 	struct btmtkuart_dev *bdev = serdev_device_get_drvdata(serdev);
 	int err;
diff --git a/drivers/bluetooth/btnxpuart.c b/drivers/bluetooth/btnxpuart.c
index b7e66b7ac570..d75487a90bba 100644
--- a/drivers/bluetooth/btnxpuart.c
+++ b/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 int btnxpuart_receive_buf(struct serdev_device *serdev, const u8 *data,
-				 size_t count)
+static ssize_t btnxpuart_receive_buf(struct serdev_device *serdev,
+				     const u8 *data, size_t count)
 {
 	struct btnxpuart_dev *nxpdev = serdev_device_get_drvdata(serdev);
 
diff --git a/drivers/bluetooth/hci_serdev.c b/drivers/bluetooth/hci_serdev.c
index f16fd79bc02b..39c8b567da3c 100644
--- a/drivers/bluetooth/hci_serdev.c
+++ b/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 int hci_uart_receive_buf(struct serdev_device *serdev, const u8 *data,
-				   size_t count)
+static ssize_t hci_uart_receive_buf(struct serdev_device *serdev,
+				    const u8 *data, size_t count)
 {
 	struct hci_uart *hu = serdev_device_get_drvdata(serdev);
 
diff --git a/drivers/gnss/serial.c b/drivers/gnss/serial.c
index 5d8e9bfb24d0..baa956494e79 100644
--- a/drivers/gnss/serial.c
+++ b/drivers/gnss/serial.c
@@ -80,8 +80,8 @@ static const struct gnss_operations gnss_serial_gnss_ops = {
 	.write_raw	= gnss_serial_write_raw,
 };
 
-static int gnss_serial_receive_buf(struct serdev_device *serdev,
-					const unsigned char *buf, size_t count)
+static ssize_t gnss_serial_receive_buf(struct serdev_device *serdev,
+				       const u8 *buf, size_t count)
 {
 	struct gnss_serial *gserial = serdev_device_get_drvdata(serdev);
 	struct gnss_device *gdev = gserial->gdev;
diff --git a/drivers/gnss/sirf.c b/drivers/gnss/sirf.c
index bcb53ccfee4d..6801a8fb2040 100644
--- a/drivers/gnss/sirf.c
+++ b/drivers/gnss/sirf.c
@@ -160,8 +160,8 @@ static const struct gnss_operations sirf_gnss_ops = {
 	.write_raw	= sirf_write_raw,
 };
 
-static int sirf_receive_buf(struct serdev_device *serdev,
-				const unsigned char *buf, size_t count)
+static ssize_t sirf_receive_buf(struct serdev_device *serdev,
+				const u8 *buf, size_t count)
 {
 	struct sirf_data *data = serdev_device_get_drvdata(serdev);
 	struct gnss_device *gdev = data->gdev;
diff --git a/drivers/greybus/gb-beagleplay.c b/drivers/greybus/gb-beagleplay.c
index 43318c1993ba..2da37ff92cf1 100644
--- a/drivers/greybus/gb-beagleplay.c
+++ b/drivers/greybus/gb-beagleplay.c
@@ -257,7 +257,7 @@ static void hdlc_rx_frame(struct gb_beagleplay *bg)
 	}
 }
 
-static int hdlc_rx(struct gb_beagleplay *bg, const u8 *data, size_t count)
+static ssize_t hdlc_rx(struct gb_beagleplay *bg, const u8 *data, size_t count)
 {
 	size_t i;
 	u8 c;
@@ -317,7 +317,8 @@ static void hdlc_deinit(struct gb_beagleplay *bg)
 	flush_work(&bg->tx_work);
 }
 
-static int gb_tty_receive(struct serdev_device *sd, const unsigned char *data, size_t count)
+static ssize_t gb_tty_receive(struct serdev_device *sd, const u8 *data,
+			      size_t count)
 {
 	struct gb_beagleplay *bg = serdev_device_get_drvdata(sd);
 
diff --git a/drivers/iio/chemical/pms7003.c b/drivers/iio/chemical/pms7003.c
index e9857d93b307..b5cf15a515d2 100644
--- a/drivers/iio/chemical/pms7003.c
+++ b/drivers/iio/chemical/pms7003.c
@@ -211,13 +211,13 @@ static bool pms7003_frame_is_okay(struct pms7003_frame *frame)
 	return checksum == pms7003_calc_checksum(frame);
 }
 
-static int pms7003_receive_buf(struct serdev_device *serdev,
-			       const unsigned char *buf, size_t size)
+static ssize_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);
 	struct pms7003_frame *frame = &state->frame;
-	int num;
+	size_t num;
 
 	if (!frame->expected_length) {
 		u16 magic;
diff --git a/drivers/iio/chemical/scd30_serial.c b/drivers/iio/chemical/scd30_serial.c
index 3c519103d30b..a47654591e55 100644
--- a/drivers/iio/chemical/scd30_serial.c
+++ b/drivers/iio/chemical/scd30_serial.c
@@ -174,13 +174,13 @@ static int scd30_serdev_command(struct scd30_state *state, enum scd30_cmd cmd, u
 	return 0;
 }
 
-static int scd30_serdev_receive_buf(struct serdev_device *serdev,
-				    const unsigned char *buf, size_t size)
+static ssize_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;
 	struct scd30_state *state;
-	int num;
+	size_t num;
 
 	if (!indio_dev)
 		return 0;
diff --git a/drivers/iio/chemical/sps30_serial.c b/drivers/iio/chemical/sps30_serial.c
index 164f4b3e025c..3afa89f8acc3 100644
--- a/drivers/iio/chemical/sps30_serial.c
+++ b/drivers/iio/chemical/sps30_serial.c
@@ -74,8 +74,8 @@ static int sps30_serial_xfer(struct sps30_state *state, const unsigned char *buf
 }
 
 static const struct {
-	unsigned char byte;
-	unsigned char byte2;
+	u8 byte;
+	u8 byte2;
 } sps30_serial_bytes[] = {
 	{ 0x11, 0x31 },
 	{ 0x13, 0x33 },
@@ -83,7 +83,7 @@ static const struct {
 	{ 0x7d, 0x5d },
 };
 
-static int sps30_serial_put_byte(unsigned char *buf, unsigned char byte)
+static int sps30_serial_put_byte(u8 *buf, u8 byte)
 {
 	int i;
 
@@ -102,7 +102,7 @@ static int sps30_serial_put_byte(unsigned char *buf, unsigned char byte)
 	return 1;
 }
 
-static char sps30_serial_get_byte(bool escaped, unsigned char byte2)
+static u8 sps30_serial_get_byte(bool escaped, u8 byte2)
 {
 	int i;
 
@@ -130,8 +130,8 @@ static unsigned char sps30_serial_calc_chksum(const unsigned char *buf, size_t n
 	return ~chksum;
 }
 
-static int sps30_serial_prep_frame(unsigned char *buf, unsigned char cmd,
-				   const unsigned char *arg, size_t arg_size)
+static int sps30_serial_prep_frame(u8 *buf, u8 cmd, const u8 *arg,
+				   size_t arg_size)
 {
 	unsigned char chksum;
 	int num = 0;
@@ -210,14 +210,14 @@ static int sps30_serial_command(struct sps30_state *state, unsigned char cmd,
 	return rsp_size;
 }
 
-static int sps30_serial_receive_buf(struct serdev_device *serdev,
-				    const unsigned char *buf, size_t size)
+static ssize_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;
 	struct sps30_state *state;
-	unsigned char byte;
 	size_t i;
+	u8 byte;
 
 	if (!indio_dev)
 		return 0;
diff --git a/drivers/iio/imu/bno055/bno055_ser_core.c b/drivers/iio/imu/bno055/bno055_ser_core.c
index 57728a568471..5677bdf4f846 100644
--- a/drivers/iio/imu/bno055/bno055_ser_core.c
+++ b/drivers/iio/imu/bno055/bno055_ser_core.c
@@ -378,12 +378,12 @@ 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 int bno055_ser_receive_buf(struct serdev_device *serdev,
-				  const unsigned char *buf, size_t size)
+static ssize_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);
-	int remaining = size;
+	size_t remaining = size;
 
 	if (size == 0)
 		return 0;
diff --git a/drivers/mfd/rave-sp.c b/drivers/mfd/rave-sp.c
index da50eba10014..b1229bb143ee 100644
--- a/drivers/mfd/rave-sp.c
+++ b/drivers/mfd/rave-sp.c
@@ -471,17 +471,17 @@ static void rave_sp_receive_frame(struct rave_sp *sp,
 		rave_sp_receive_reply(sp, data, length);
 }
 
-static int rave_sp_receive_buf(struct serdev_device *serdev,
-			       const unsigned char *buf, size_t size)
+static ssize_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);
 	struct rave_sp_deframer *deframer = &sp->deframer;
-	const unsigned char *src = buf;
-	const unsigned char *end = buf + size;
+	const u8 *src = buf;
+	const u8 *end = buf + size;
 
 	while (src < end) {
-		const unsigned char byte = *src++;
+		const u8 byte = *src++;
 
 		switch (deframer->state) {
 		case RAVE_SP_EXPECT_SOF:
diff --git a/drivers/net/ethernet/qualcomm/qca_uart.c b/drivers/net/ethernet/qualcomm/qca_uart.c
index 9adec91f35e9..223321897b96 100644
--- a/drivers/net/ethernet/qualcomm/qca_uart.c
+++ b/drivers/net/ethernet/qualcomm/qca_uart.c
@@ -58,9 +58,8 @@ struct qcauart {
 	unsigned char *tx_buffer;
 };
 
-static int
-qca_tty_receive(struct serdev_device *serdev, const unsigned char *data,
-		size_t count)
+static ssize_t
+qca_tty_receive(struct serdev_device *serdev, const u8 *data, size_t count)
 {
 	struct qcauart *qca = serdev_device_get_drvdata(serdev);
 	struct net_device *netdev = qca->net_dev;
diff --git a/drivers/nfc/pn533/uart.c b/drivers/nfc/pn533/uart.c
index a556acdb947b..2eb5978bd79e 100644
--- a/drivers/nfc/pn533/uart.c
+++ b/drivers/nfc/pn533/uart.c
@@ -203,8 +203,8 @@ static int pn532_uart_rx_is_frame(struct sk_buff *skb)
 	return 0;
 }
 
-static int pn532_receive_buf(struct serdev_device *serdev,
-		const unsigned char *data, size_t count)
+static ssize_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;
diff --git a/drivers/nfc/s3fwrn5/uart.c b/drivers/nfc/s3fwrn5/uart.c
index 82ea35d748a5..456d3947116c 100644
--- a/drivers/nfc/s3fwrn5/uart.c
+++ b/drivers/nfc/s3fwrn5/uart.c
@@ -51,9 +51,8 @@ static const struct s3fwrn5_phy_ops uart_phy_ops = {
 	.write = s3fwrn82_uart_write,
 };
 
-static int s3fwrn82_uart_read(struct serdev_device *serdev,
-			      const unsigned char *data,
-			      size_t count)
+static ssize_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;
diff --git a/drivers/platform/chrome/cros_ec_uart.c b/drivers/platform/chrome/cros_ec_uart.c
index 788246559bbb..68d80559fddc 100644
--- a/drivers/platform/chrome/cros_ec_uart.c
+++ b/drivers/platform/chrome/cros_ec_uart.c
@@ -81,9 +81,8 @@ struct cros_ec_uart {
 	struct response_info response;
 };
 
-static int cros_ec_uart_rx_bytes(struct serdev_device *serdev,
-				 const u8 *data,
-				 size_t count)
+static ssize_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);
diff --git a/drivers/platform/surface/aggregator/controller.h b/drivers/platform/surface/aggregator/controller.h
index f0d987abc51e..f1638c2081e8 100644
--- a/drivers/platform/surface/aggregator/controller.h
+++ b/drivers/platform/surface/aggregator/controller.h
@@ -238,8 +238,8 @@ struct ssam_controller {
  * layer of the controller has been shut down, %-ESHUTDOWN.
  */
 static inline
-int ssam_controller_receive_buf(struct ssam_controller *ctrl,
-				const unsigned char *buf, size_t n)
+ssize_t ssam_controller_receive_buf(struct ssam_controller *ctrl, const u8 *buf,
+				    size_t n)
 {
 	return ssh_ptl_rx_rcvbuf(&ctrl->rtl.ptl, buf, n);
 }
diff --git a/drivers/platform/surface/aggregator/core.c b/drivers/platform/surface/aggregator/core.c
index 1a6373dea109..72d7314a4efd 100644
--- a/drivers/platform/surface/aggregator/core.c
+++ b/drivers/platform/surface/aggregator/core.c
@@ -227,8 +227,8 @@ EXPORT_SYMBOL_GPL(ssam_client_bind);
 
 /* -- Glue layer (serdev_device -> ssam_controller). ------------------------ */
 
-static int ssam_receive_buf(struct serdev_device *dev, const unsigned char *buf,
-			    size_t n)
+static ssize_t ssam_receive_buf(struct serdev_device *dev, const u8 *buf,
+				size_t n)
 {
 	struct ssam_controller *ctrl;
 
diff --git a/drivers/platform/surface/aggregator/ssh_packet_layer.c b/drivers/platform/surface/aggregator/ssh_packet_layer.c
index def8d7ac541f..d726b1a86319 100644
--- a/drivers/platform/surface/aggregator/ssh_packet_layer.c
+++ b/drivers/platform/surface/aggregator/ssh_packet_layer.c
@@ -1887,9 +1887,9 @@ int ssh_ptl_rx_stop(struct ssh_ptl *ptl)
  * Return: Returns the number of bytes transferred (positive or zero) on
  * success. Returns %-ESHUTDOWN if the packet layer has been shut down.
  */
-int ssh_ptl_rx_rcvbuf(struct ssh_ptl *ptl, const u8 *buf, size_t n)
+ssize_t ssh_ptl_rx_rcvbuf(struct ssh_ptl *ptl, const u8 *buf, size_t n)
 {
-	int used;
+	size_t used;
 
 	if (test_bit(SSH_PTL_SF_SHUTDOWN_BIT, &ptl->state))
 		return -ESHUTDOWN;
diff --git a/drivers/platform/surface/aggregator/ssh_packet_layer.h b/drivers/platform/surface/aggregator/ssh_packet_layer.h
index 64633522f971..c80e822070df 100644
--- a/drivers/platform/surface/aggregator/ssh_packet_layer.h
+++ b/drivers/platform/surface/aggregator/ssh_packet_layer.h
@@ -162,7 +162,7 @@ void ssh_ptl_shutdown(struct ssh_ptl *ptl);
 int ssh_ptl_submit(struct ssh_ptl *ptl, struct ssh_packet *p);
 void ssh_ptl_cancel(struct ssh_packet *p);
 
-int ssh_ptl_rx_rcvbuf(struct ssh_ptl *ptl, const u8 *buf, size_t n);
+ssize_t ssh_ptl_rx_rcvbuf(struct ssh_ptl *ptl, const u8 *buf, size_t n);
 
 /**
  * ssh_ptl_tx_wakeup_transfer() - Wake up packet transmitter thread for
diff --git a/drivers/tty/serdev/core.c b/drivers/tty/serdev/core.c
index 3090e3454c44..de8d87d4858d 100644
--- a/drivers/tty/serdev/core.c
+++ b/drivers/tty/serdev/core.c
@@ -225,8 +225,7 @@ EXPORT_SYMBOL_GPL(serdev_device_write_wakeup);
  * Return: The number of bytes written (less than count if not enough room in
  * the write buffer), or a negative errno on errors.
  */
-int serdev_device_write_buf(struct serdev_device *serdev,
-			    const unsigned char *buf, size_t count)
+int serdev_device_write_buf(struct serdev_device *serdev, const u8 *buf, size_t count)
 {
 	struct serdev_controller *ctrl = serdev->ctrl;
 
@@ -259,13 +258,12 @@ EXPORT_SYMBOL_GPL(serdev_device_write_buf);
  * -ETIMEDOUT or -ERESTARTSYS if interrupted before any bytes were written, or
  * a negative errno on errors.
  */
-int serdev_device_write(struct serdev_device *serdev,
-			const unsigned char *buf, size_t count,
-			long timeout)
+ssize_t serdev_device_write(struct serdev_device *serdev, const u8 *buf,
+			    size_t count, long timeout)
 {
 	struct serdev_controller *ctrl = serdev->ctrl;
-	int written = 0;
-	int ret;
+	size_t written = 0;
+	ssize_t ret;
 
 	if (!ctrl || !ctrl->ops->write_buf || !serdev->ops->write_wakeup)
 		return -EINVAL;
diff --git a/include/linux/serdev.h b/include/linux/serdev.h
index 8cdab2c3b6d5..3fab88ba265e 100644
--- a/include/linux/serdev.h
+++ b/include/linux/serdev.h
@@ -27,7 +27,7 @@ struct serdev_device;
  *			not sleep.
  */
 struct serdev_device_ops {
-	int (*receive_buf)(struct serdev_device *, const unsigned char *, size_t);
+	ssize_t (*receive_buf)(struct serdev_device *, const u8 *, size_t);
 	void (*write_wakeup)(struct serdev_device *);
 };
 
@@ -204,13 +204,13 @@ void serdev_device_close(struct serdev_device *);
 int devm_serdev_device_open(struct device *, struct serdev_device *);
 unsigned int serdev_device_set_baudrate(struct serdev_device *, unsigned int);
 void serdev_device_set_flow_control(struct serdev_device *, bool);
-int serdev_device_write_buf(struct serdev_device *, const unsigned char *, size_t);
+int serdev_device_write_buf(struct serdev_device *, const u8 *, size_t);
 void serdev_device_wait_until_sent(struct serdev_device *, long);
 int serdev_device_get_tiocm(struct serdev_device *);
 int serdev_device_set_tiocm(struct serdev_device *, int, int);
 int serdev_device_break_ctl(struct serdev_device *serdev, int break_state);
 void serdev_device_write_wakeup(struct serdev_device *);
-int serdev_device_write(struct serdev_device *, const unsigned char *, size_t, long);
+ssize_t serdev_device_write(struct serdev_device *, const u8 *, size_t, long);
 void serdev_device_write_flush(struct serdev_device *);
 int serdev_device_write_room(struct serdev_device *);
 
@@ -248,7 +248,7 @@ static inline unsigned int serdev_device_set_baudrate(struct serdev_device *sdev
 }
 static inline void serdev_device_set_flow_control(struct serdev_device *sdev, bool enable) {}
 static inline int serdev_device_write_buf(struct serdev_device *serdev,
-					  const unsigned char *buf,
+					  const u8 *buf,
 					  size_t count)
 {
 	return -ENODEV;
@@ -266,8 +266,9 @@ static inline int serdev_device_break_ctl(struct serdev_device *serdev, int brea
 {
 	return -EOPNOTSUPP;
 }
-static inline int serdev_device_write(struct serdev_device *sdev, const unsigned char *buf,
-				      size_t count, unsigned long timeout)
+static inline ssize_t serdev_device_write(struct serdev_device *sdev,
+					  const u8 *buf, size_t count,
+					  unsigned long timeout)
 {
 	return -ENODEV;
 }
diff --git a/sound/drivers/serial-generic.c b/sound/drivers/serial-generic.c
index c8db6c75d133..d6e5aafd697c 100644
--- a/sound/drivers/serial-generic.c
+++ b/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 int snd_serial_generic_receive_buf(struct serdev_device *serdev,
-				const unsigned char *buf, size_t count)
+static ssize_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);
-- 
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