[PATCH 1/1 v7] usb: serial: add support for CH348

[Corentin Labbe]

The CH348 is an USB octo port serial adapter.
The device multiplexes all 8 ports in the same pair of Bulk endpoints.
Since there is no public datasheet, unfortunately it remains some magic values

Signed-off-by: Corentin Labbe <clabbe@xxxxxxxxxxxx>
---
 drivers/usb/serial/Kconfig  |   9 +
 drivers/usb/serial/Makefile |   1 +
 drivers/usb/serial/ch348.c  | 725 ++++++++++++++++++++++++++++++++++++
 3 files changed, 735 insertions(+)
 create mode 100644 drivers/usb/serial/ch348.c

diff --git a/drivers/usb/serial/Kconfig b/drivers/usb/serial/Kconfig
index ef8d1c73c754..1e1842656b54 100644
--- a/drivers/usb/serial/Kconfig
+++ b/drivers/usb/serial/Kconfig
@@ -112,6 +112,15 @@ config USB_SERIAL_CH341
 	  To compile this driver as a module, choose M here: the
 	  module will be called ch341.
 
+config USB_SERIAL_CH348
+	tristate "USB Winchiphead CH348 Octo Port Serial Driver"
+	help
+	  Say Y here if you want to use a Winchiphead CH348 octo port
+	  USB to serial adapter.
+
+	  To compile this driver as a module, choose M here: the
+	  module will be called ch348.
+
 config USB_SERIAL_WHITEHEAT
 	tristate "USB ConnectTech WhiteHEAT Serial Driver"
 	select USB_EZUSB_FX2
diff --git a/drivers/usb/serial/Makefile b/drivers/usb/serial/Makefile
index c7bb1a88173e..d16ff59fde68 100644
--- a/drivers/usb/serial/Makefile
+++ b/drivers/usb/serial/Makefile
@@ -15,6 +15,7 @@ obj-$(CONFIG_USB_SERIAL_AIRCABLE)		+= aircable.o
 obj-$(CONFIG_USB_SERIAL_ARK3116)		+= ark3116.o
 obj-$(CONFIG_USB_SERIAL_BELKIN)			+= belkin_sa.o
 obj-$(CONFIG_USB_SERIAL_CH341)			+= ch341.o
+obj-$(CONFIG_USB_SERIAL_CH348)			+= ch348.o
 obj-$(CONFIG_USB_SERIAL_CP210X)			+= cp210x.o
 obj-$(CONFIG_USB_SERIAL_CYBERJACK)		+= cyberjack.o
 obj-$(CONFIG_USB_SERIAL_CYPRESS_M8)		+= cypress_m8.o
diff --git a/drivers/usb/serial/ch348.c b/drivers/usb/serial/ch348.c
new file mode 100644
index 000000000000..e437ba36bb5e
--- /dev/null
+++ b/drivers/usb/serial/ch348.c
@@ -0,0 +1,725 @@
+// SPDX-License-Identifier: GPL-2.0
+/*
+ * USB serial driver for USB to Octal UARTs chip ch348.
+ *
+ * Copyright (C) 2022 Corentin Labbe <clabbe@xxxxxxxxxxxx>
+ * With the help of Neil Armstrong <neil.armstrong@xxxxxxxxxx>
+ * and the help of Martin Blumenstingl <martin.blumenstingl@xxxxxxxxxxxxxx>
+ */
+
+#include <linux/completion.h>
+#include <linux/errno.h>
+#include <linux/init.h>
+#include <linux/kernel.h>
+#include <linux/module.h>
+#include <linux/mutex.h>
+#include <linux/overflow.h>
+#include <linux/serial.h>
+#include <linux/slab.h>
+#include <linux/tty.h>
+#include <linux/tty_driver.h>
+#include <linux/tty_flip.h>
+#include <linux/usb.h>
+#include <linux/usb/serial.h>
+
+#define CH348_CMD_TIMEOUT   2000
+
+#define CH348_CTO_D	0x01
+#define CH348_CTO_R	0x02
+
+#define CH348_CTI_C	0x10
+#define CH348_CTI_DSR	0x20
+#define CH348_CTI_R	0x40
+#define CH348_CTI_DCD	0x80
+
+#define CH348_LO	0x02
+#define CH348_LP	0x04
+#define CH348_LF	0x08
+#define CH348_LB	0x10
+
+#define CMD_W_R		0xC0
+#define CMD_W_BR	0x80
+
+#define CMD_WB_E	0x90
+#define CMD_RB_E	0xC0
+
+#define M_NOR		0x00
+#define M_HF		0x03
+
+#define R_MOD		0x97
+#define R_IO_D		0x98
+#define R_IO_O		0x99
+#define R_IO_I		0x9b
+#define R_TM_O		0x9c
+#define R_INIT		0xa1
+
+#define R_C1		0x01
+#define R_C2		0x02
+#define R_C4		0x04
+#define R_C5		0x06
+
+#define R_II_B1		0x06
+#define R_II_B2		0x02
+#define R_II_B3		0x00
+
+#define CMD_VER		0x96
+
+#define CH348_RX_PORT_CHUNK_LENGTH	32
+#define CH348_RX_PORT_MAX_LENGTH	30
+
+struct ch348_rxbuf {
+	u8 port;
+	u8 length;
+	u8 data[CH348_RX_PORT_MAX_LENGTH];
+} __packed;
+
+struct ch348_txbuf {
+	u8 port;
+	__le16 length;
+	u8 data[];
+} __packed;
+
+#define CH348_TX_HDRSIZE offsetof(struct ch348_txbuf, data)
+
+struct ch348_initbuf {
+	u8 cmd;
+	u8 reg;
+	u8 port;
+	__be32 baudrate;
+	u8 format;
+	u8 paritytype;
+	u8 databits;
+	u8 rate;
+	u8 unknown;
+} __packed;
+
+#define CH348_MAXPORT 8
+
+/*
+ * The CH348 multiplexes rx & tx into a pair of Bulk USB endpoints for
+ * the 8 serial ports, and another pair of Bulk USB endpoints to
+ * set port settings and receive port status events.
+ *
+ * The USB serial cores ties every Bulk endpoints pairs to each ports,
+ * but in our case it will set port 0 with the rx/tx endpoints
+ * and port 1 with the setup/status endpoints.
+ *
+ * To still take advantage of the generic code, we (re-)initialize
+ * the USB serial port structure with the correct USB endpoint
+ * for read and write, and write proper process_read_urb()
+ * and prepare_write_buffer() to correctly (de-)multiplex data.
+ * Also we use a custom write() implementation to wait until the buffer
+ * has been fully transmitted to prevent TX buffer overruns.
+ */
+
+/*
+ * struct ch348_port - per-port information
+ * @uartmode:		UART port current mode
+ * @write_completion:	completion event when the TX buffer has been written out
+ */
+struct ch348_port {
+	u8 uartmode;
+	struct completion write_completion;
+};
+
+/*
+ * struct ch348 - main container for all this driver information
+ * @udev:		pointer to the CH348 USB device
+ * @ports:		List of per-port information
+ * @serial:		pointer to the serial structure
+ * @write_lock:		protect against concurrent writes so we don't lose data
+ * @cmd_ep:		endpoint number for configure operations
+ * @status_urb:		URB for status
+ * @status_buffer:	buffer used by status_urb
+ */
+struct ch348 {
+	struct usb_device *udev;
+	struct ch348_port ports[CH348_MAXPORT];
+	struct usb_serial *serial;
+
+	struct mutex write_lock;
+
+	int cmd_ep;
+
+	struct urb *status_urb;
+	u8 status_buffer[];
+};
+
+struct ch348_magic {
+	u8 action;
+	u8 reg;
+	u8 control;
+} __packed;
+
+struct ch348_status_entry {
+	u8 portnum:4;
+	u8 unused:4;
+	u8 reg_iir;
+	union {
+		u8 lsr_signal;
+		u8 modem_signal;
+		u8 init_data[10];
+	};
+} __packed;
+
+static void ch348_process_status_urb(struct urb *urb)
+{
+	struct ch348_status_entry *status_entry;
+	struct ch348 *ch348 = urb->context;
+	int ret, status = urb->status;
+	struct usb_serial_port *port;
+	unsigned int i, status_len;
+
+	switch (status) {
+	case 0:
+		/* success */
+		break;
+	case -ECONNRESET:
+	case -ENOENT:
+	case -ESHUTDOWN:
+		/* this urb is terminated, clean up */
+		dev_dbg(&urb->dev->dev, "%s - urb shutting down with status: %d\n",
+			__func__, status);
+		return;
+	default:
+		dev_err(&urb->dev->dev, "%s - nonzero urb status received: %d\n",
+			__func__, status);
+		goto exit;
+	}
+
+	if (urb->actual_length < 3) {
+		dev_warn(&ch348->udev->dev,
+			 "Received too short status buffer with %u bytes\n",
+			 urb->actual_length);
+		goto exit;
+	}
+
+	for (i = 0; i < urb->actual_length;) {
+		status_entry = urb->transfer_buffer + i;
+
+		if (status_entry->portnum >= CH348_MAXPORT) {
+			dev_warn(&ch348->udev->dev,
+				 "Invalid port %d in status entry\n",
+				 status_entry->portnum);
+			break;
+		}
+
+		port = ch348->serial->port[status_entry->portnum];
+		status_len = 3;
+
+		if (!status_entry->reg_iir) {
+			dev_dbg(&port->dev, "Ignoring status with zero reg_iir\n");
+		} else if (status_entry->reg_iir == R_INIT) {
+			status_len = 12;
+		} else if ((status_entry->reg_iir & 0x0f) == R_II_B1) {
+			if (status_entry->lsr_signal & CH348_LO)
+				port->icount.overrun++;
+			if (status_entry->lsr_signal & CH348_LP)
+				port->icount.parity++;
+			if (status_entry->lsr_signal & CH348_LF)
+				port->icount.frame++;
+			if (status_entry->lsr_signal & CH348_LF)
+				port->icount.brk++;
+		} else if ((status_entry->reg_iir & 0x0f) == R_II_B2) {
+			complete_all(&ch348->ports[status_entry->portnum].write_completion);
+		} else {
+			dev_warn(&port->dev,
+				 "Unsupported status with reg_iir 0x%02x\n",
+				 status_entry->reg_iir);
+		}
+
+		usb_serial_debug_data(&port->dev, __func__, status_len,
+				      urb->transfer_buffer + i);
+
+		i += status_len;
+	}
+
+exit:
+	ret = usb_submit_urb(urb, GFP_ATOMIC);
+	if (ret)
+		dev_err(&urb->dev->dev, "%s - usb_submit_urb failed; %d\n",
+			__func__, ret);
+}
+
+/*
+ * Some values came from vendor tree, and we have no meaning for them, this
+ * function simply use them.
+ */
+static int ch348_do_magic(struct ch348 *ch348, int portnum, u8 action, u8 reg, u8 control)
+{
+	struct ch348_magic *buffer;
+	int ret, len;
+
+	buffer = kzalloc(sizeof(*buffer), GFP_KERNEL);
+	if (!buffer)
+		return -ENOMEM;
+
+	if (portnum < 4)
+		reg += 0x10 * portnum;
+	else
+		reg += 0x10 * (portnum - 4) + 0x08;
+
+	buffer->action = action;
+	buffer->reg = reg;
+	buffer->control = control;
+
+	ret = usb_bulk_msg(ch348->udev, ch348->cmd_ep, buffer, 3, &len,
+			   CH348_CMD_TIMEOUT);
+	if (ret)
+		dev_err(&ch348->udev->dev, "Failed to write magic err=%d\n", ret);
+
+	kfree(buffer);
+
+	return ret;
+}
+
+static int ch348_configure(struct ch348 *ch348, int portnum)
+{
+	int ret;
+
+	ret = ch348_do_magic(ch348, portnum, CMD_W_R, R_C2, 0x87);
+	if (ret)
+		return ret;
+
+	return ch348_do_magic(ch348, portnum, CMD_W_R, R_C4, 0x08);
+}
+
+static void ch348_process_read_urb(struct urb *urb)
+{
+	struct usb_serial_port *port = urb->context;
+	struct ch348 *ch348 = usb_get_serial_data(port->serial);
+	unsigned int portnum, usblen, i;
+	struct ch348_rxbuf *rxb;
+
+	if (urb->actual_length < 2) {
+		dev_dbg(&ch348->udev->dev, "Empty rx buffer\n");
+		return;
+	}
+
+	for (i = 0; i < urb->actual_length; i += CH348_RX_PORT_CHUNK_LENGTH) {
+		rxb = urb->transfer_buffer + i;
+		portnum = rxb->port;
+		if (portnum >= CH348_MAXPORT) {
+			dev_dbg(&ch348->udev->dev, "Invalid port %d\n", portnum);
+			break;
+		}
+
+		port = ch348->serial->port[portnum];
+
+		usblen = rxb->length;
+		if (usblen > CH348_RX_PORT_MAX_LENGTH) {
+			dev_dbg(&port->dev, "Invalid length %d for port %d\n",
+				usblen, portnum);
+			break;
+		}
+
+		tty_insert_flip_string(&port->port, rxb->data, usblen);
+		tty_flip_buffer_push(&port->port);
+		port->icount.rx += usblen;
+		usb_serial_debug_data(&port->dev, __func__, usblen, rxb->data);
+	}
+}
+
+static int ch348_prepare_write_buffer(struct usb_serial_port *port, void *dest, size_t size)
+{
+	struct ch348_txbuf *rxt = dest;
+	int count;
+
+	count = kfifo_out_locked(&port->write_fifo, rxt->data,
+				 size - CH348_TX_HDRSIZE, &port->lock);
+
+	rxt->port = port->port_number;
+	rxt->length = cpu_to_le16(count);
+
+	return count + CH348_TX_HDRSIZE;
+}
+
+static int ch348_write(struct tty_struct *tty, struct usb_serial_port *port,
+		       const unsigned char *buf, int count)
+{
+	struct ch348 *ch348 = usb_get_serial_data(port->serial);
+	struct ch348_port *ch348_port = &ch348->ports[port->port_number];
+	int ret, max_tx_size;
+
+	if (tty_get_baud_rate(tty) < 9600 && count >= 128)
+		/*
+		 * Writing larger buffers can take longer than the hardware
+		 * allows before discarding the write buffer. Limit the
+		 * transfer size in such cases.
+		 * These values have been found by empirical testing.
+		 */
+		max_tx_size = 128;
+	else
+		/*
+		* Only ingest as many bytes as we can transfer with one URB at
+		* a time. Once an URB has been written we need to wait for the
+		* R_II_B2 status event before we are allowed to send more data.
+		* If we ingest more data then usb_serial_generic_write() will
+		* internally try to process as much data as possible with any
+		* number of URBs without giving us the chance to wait in
+		* between transfers.
+		*/
+		max_tx_size = port->bulk_out_size - CH348_TX_HDRSIZE;
+
+	reinit_completion(&ch348_port->write_completion);
+
+	mutex_lock(&ch348->write_lock);
+
+	/*
+	 * For any (remaining) bytes that we did not transfer TTY core will
+	 * call us again, with the buffer and count adjusted to the remaining
+	 * data.
+	 */
+	ret = usb_serial_generic_write(tty, port, buf, min(count, max_tx_size));
+
+	mutex_unlock(&ch348->write_lock);
+
+	if (ret <= 0)
+		return ret;
+
+	if (!wait_for_completion_interruptible_timeout(&ch348_port->write_completion,
+						       msecs_to_jiffies(CH348_CMD_TIMEOUT))) {
+		dev_err_console(port, "Failed to wait for TX buffer flush\n");
+		return -ETIMEDOUT;
+	}
+
+	return ret;
+}
+
+static int ch348_set_uartmode(struct ch348 *ch348, int portnum, u8 mode)
+{
+	int ret;
+
+	if (ch348->ports[portnum].uartmode == M_NOR && mode == M_HF) {
+		ret = ch348_do_magic(ch348, portnum, CMD_W_BR, R_C4, 0x51);
+		if (ret)
+			return ret;
+		ch348->ports[portnum].uartmode = M_HF;
+	}
+
+	if (ch348->ports[portnum].uartmode == M_HF && mode == M_NOR) {
+		ret = ch348_do_magic(ch348, portnum, CMD_W_BR, R_C4, 0x50);
+		if (ret)
+			return ret;
+		ch348->ports[portnum].uartmode = M_NOR;
+	}
+	return 0;
+}
+
+static void ch348_set_termios(struct tty_struct *tty, struct usb_serial_port *port,
+			      const struct ktermios *termios_old)
+{
+	struct ch348 *ch348 = usb_get_serial_data(port->serial);
+	struct ktermios *termios = &tty->termios;
+	int ret, portnum = port->port_number;
+	struct ch348_initbuf *buffer;
+	speed_t	baudrate;
+	u8 format;
+
+	if (termios_old && !tty_termios_hw_change(&tty->termios, termios_old))
+		return;
+
+	buffer = kzalloc(sizeof(*buffer), GFP_KERNEL);
+	if (!buffer) {
+		if (termios_old)
+			tty->termios = *termios_old;
+		return;
+	}
+
+	/*
+	 * The datasheet states that only baud rates in range of 1200..6000000
+	 * are supported. Tests however show that even baud rates as low as 50
+	 * and as high as 12000000 are working in practice.
+	 */
+	baudrate = clamp(tty_get_baud_rate(tty), 50, 12000000);
+
+	format = termios->c_cflag & CSTOPB ? 2 : 1;
+
+	buffer->paritytype = 0;
+	if (termios->c_cflag & PARENB) {
+		if (termios->c_cflag & PARODD)
+			buffer->paritytype += 1;
+		else
+			buffer->paritytype += 2;
+		if  (termios->c_cflag & CMSPAR)
+			buffer->paritytype += 2;
+	}
+
+	switch (C_CSIZE(tty)) {
+	case CS5:
+		buffer->databits = 5;
+		break;
+	case CS6:
+		buffer->databits = 6;
+		break;
+	case CS7:
+		buffer->databits = 7;
+		break;
+	case CS8:
+	default:
+		buffer->databits = 8;
+		break;
+	}
+	buffer->cmd = CMD_WB_E | (portnum & 0x0F);
+	buffer->reg = R_INIT;
+	buffer->port = portnum;
+	buffer->baudrate = cpu_to_be32(baudrate);
+
+	if (format == 2)
+		buffer->format = 0x02;
+	else if (format == 1)
+		buffer->format = 0x00;
+
+	buffer->rate = max_t(speed_t, 5, (10000 * 15 / baudrate) + 1);
+
+	ret = usb_bulk_msg(ch348->udev, ch348->cmd_ep, buffer,
+			   sizeof(*buffer), NULL, CH348_CMD_TIMEOUT);
+	if (ret < 0) {
+		dev_err(&ch348->udev->dev, "Failed to change line settings: err=%d\n",
+			ret);
+		goto out;
+	}
+
+	ret = ch348_do_magic(ch348, portnum, CMD_W_R, R_C1, 0x0F);
+	if (ret < 0)
+		goto out;
+
+	if (C_CRTSCTS(tty))
+		ret = ch348_set_uartmode(ch348, portnum, M_HF);
+	else
+		ret = ch348_set_uartmode(ch348, portnum, M_NOR);
+
+out:
+	kfree(buffer);
+}
+
+static int ch348_open(struct tty_struct *tty, struct usb_serial_port *port)
+{
+	struct ch348 *ch348 = usb_get_serial_data(port->serial);
+	int ret;
+
+	if (tty)
+		ch348_set_termios(tty, port, NULL);
+
+	ret = ch348_configure(ch348, port->port_number);
+	if (ret) {
+		dev_err(&ch348->udev->dev, "Fail to configure err=%d\n", ret);
+		return ret;
+	}
+
+	return usb_serial_generic_open(tty, port);
+}
+
+static int ch348_attach(struct usb_serial *serial)
+{
+	struct usb_endpoint_descriptor *epcmd, *epstatus;
+	struct usb_serial_port *port0 = serial->port[1];
+	struct usb_device *usb_dev = serial->dev;
+	int status_buffer_size, i, ret;
+	struct usb_interface *intf;
+	struct ch348 *ch348;
+
+	intf = usb_ifnum_to_if(usb_dev, 0);
+	epstatus = &intf->cur_altsetting->endpoint[2].desc;
+	epcmd = &intf->cur_altsetting->endpoint[3].desc;
+
+	status_buffer_size = usb_endpoint_maxp(epstatus);
+
+	ch348 = kzalloc(struct_size(ch348, status_buffer, status_buffer_size),
+			GFP_KERNEL);
+	if (!ch348)
+		return -ENOMEM;
+
+	usb_set_serial_data(serial, ch348);
+
+	ch348->udev = serial->dev;
+	ch348->serial = serial;
+	mutex_init(&ch348->write_lock);
+
+	for (i = 0; i < CH348_MAXPORT; i++)
+		init_completion(&ch348->ports[i].write_completion);
+
+	ch348->status_urb = usb_alloc_urb(0, GFP_KERNEL);
+	if (!ch348->status_urb) {
+		ret = -ENOMEM;
+		goto err_free_ch348;
+	}
+
+	usb_fill_bulk_urb(ch348->status_urb, ch348->udev,
+			  usb_rcvbulkpipe(ch348->udev, epstatus->bEndpointAddress),
+			  ch348->status_buffer, status_buffer_size,
+			  ch348_process_status_urb, ch348);
+
+	ret = usb_submit_urb(ch348->status_urb, GFP_KERNEL);
+	if (ret) {
+		dev_err(&ch348->udev->dev,
+			"%s - failed to submit status/interrupt urb %i\n",
+			__func__, ret);
+		goto err_free_status_urb;
+	}
+
+	ret = usb_serial_generic_submit_read_urbs(port0, GFP_KERNEL);
+	if (ret)
+		goto err_kill_status_urb;
+
+	ch348->cmd_ep = usb_sndbulkpipe(usb_dev, epcmd->bEndpointAddress);
+
+	return 0;
+
+err_kill_status_urb:
+	usb_kill_urb(ch348->status_urb);
+err_free_status_urb:
+	usb_free_urb(ch348->status_urb);
+err_free_ch348:
+	kfree(ch348);
+	return ret;
+}
+
+static void ch348_release(struct usb_serial *serial)
+{
+	struct ch348 *ch348 = usb_get_serial_data(serial);
+
+	usb_kill_urb(ch348->status_urb);
+	usb_free_urb(ch348->status_urb);
+
+	kfree(ch348);
+}
+
+static void ch348_print_version(struct usb_serial *serial)
+{
+	u8 *version_buf;
+	int ret;
+
+	version_buf = kzalloc(4, GFP_KERNEL);
+	if (!version_buf)
+		return;
+
+	ret = usb_control_msg(serial->dev, usb_rcvctrlpipe(serial->dev, 0),
+			      CMD_VER,
+			      USB_TYPE_VENDOR | USB_RECIP_DEVICE | USB_DIR_IN,
+			      0, 0, version_buf, 4, CH348_CMD_TIMEOUT);
+	if (ret < 0)
+		dev_dbg(&serial->dev->dev, "Failed to read CMD_VER: %d\n", ret);
+	else
+		dev_info(&serial->dev->dev, "Found WCH CH348%s\n",
+			 (version_buf[1] & 0x80) ? "Q" : "L");
+
+	kfree(version_buf);
+}
+
+static int ch348_probe(struct usb_serial *serial, const struct usb_device_id *id)
+{
+	struct usb_endpoint_descriptor *epread, *epwrite, *epstatus, *epcmd;
+	struct usb_device *usb_dev = serial->dev;
+	struct usb_interface *intf;
+	int ret;
+
+	intf = usb_ifnum_to_if(usb_dev, 0);
+
+	ret = usb_find_common_endpoints(intf->cur_altsetting, &epread, &epwrite,
+					NULL, NULL);
+	if (ret) {
+		dev_err(&serial->dev->dev, "Failed to find basic endpoints ret=%d\n", ret);
+		return ret;
+	}
+
+	epstatus = &intf->cur_altsetting->endpoint[2].desc;
+	if (!usb_endpoint_is_bulk_in(epstatus)) {
+		dev_err(&serial->dev->dev, "Missing second bulk in (STATUS/INT)\n");
+		return -ENODEV;
+	}
+
+	epcmd = &intf->cur_altsetting->endpoint[3].desc;
+	if (!usb_endpoint_is_bulk_out(epcmd)) {
+		dev_err(&serial->dev->dev, "Missing second bulk out (CMD)\n");
+		return -ENODEV;
+	}
+
+	ch348_print_version(serial);
+
+	return 0;
+}
+
+static int ch348_calc_num_ports(struct usb_serial *serial,
+				struct usb_serial_endpoints *epds)
+{
+	int i;
+
+	for (i = 1; i < CH348_MAXPORT; ++i) {
+		epds->bulk_out[i] = epds->bulk_out[0];
+		epds->bulk_in[i] = epds->bulk_in[0];
+	}
+
+	epds->num_bulk_out = CH348_MAXPORT;
+	epds->num_bulk_in = CH348_MAXPORT;
+
+	return CH348_MAXPORT;
+}
+
+static int ch348_suspend(struct usb_serial *serial, pm_message_t message)
+{
+	struct ch348 *ch348 = usb_get_serial_data(serial);
+
+	usb_kill_urb(ch348->status_urb);
+
+	return 0;
+}
+
+static int ch348_resume(struct usb_serial *serial)
+{
+	struct ch348 *ch348 = usb_get_serial_data(serial);
+	int ret;
+
+	ret = usb_submit_urb(ch348->status_urb, GFP_KERNEL);
+	if (ret) {
+		dev_err(&ch348->udev->dev,
+			"%s - failed to submit status/interrupt urb %i\n",
+			__func__, ret);
+		return ret;
+	}
+
+	ret = usb_serial_generic_resume(serial);
+	if (ret)
+		usb_kill_urb(ch348->status_urb);
+
+	return ret;
+}
+
+static const struct usb_device_id ch348_ids[] = {
+	{ USB_DEVICE(0x1a86, 0x55d9), },
+	{ /* sentinel */ }
+};
+
+MODULE_DEVICE_TABLE(usb, ch348_ids);
+
+static struct usb_serial_driver ch348_device = {
+	.driver = {
+		.owner = THIS_MODULE,
+		.name = "ch348",
+	},
+	.id_table =		ch348_ids,
+	.num_ports =		CH348_MAXPORT,
+	.num_bulk_in =		1,
+	.num_bulk_out =		1,
+	.open =			ch348_open,
+	.set_termios =		ch348_set_termios,
+	.process_read_urb =	ch348_process_read_urb,
+	.prepare_write_buffer =	ch348_prepare_write_buffer,
+	.write =		ch348_write,
+	.probe =		ch348_probe,
+	.calc_num_ports =	ch348_calc_num_ports,
+	.attach =		ch348_attach,
+	.release =		ch348_release,
+	.suspend =		ch348_suspend,
+	.resume =		ch348_resume,
+};
+
+static struct usb_serial_driver * const serial_drivers[] = {
+	&ch348_device, NULL
+};
+
+module_usb_serial_driver(serial_drivers, ch348_ids);
+
+MODULE_AUTHOR("Corentin Labbe <clabbe@xxxxxxxxxxxx>");
+MODULE_DESCRIPTION("USB CH348 Octo port serial converter driver");
+MODULE_LICENSE("GPL");
-- 
2.43.2