Message-ID: <Zp5q5V_OnLAdvBrU@hovoldconsulting.com>
Date: Mon, 22 Jul 2024 16:21:25 +0200
From: Johan Hovold <johan@...nel.org>
To: Corentin Labbe <clabbe@...libre.com>
Cc: gregkh@...uxfoundation.org, linux-kernel@...r.kernel.org,
	linux-usb@...r.kernel.org, martin.blumenstingl@...glemail.com,
	david@...t.cz
Subject: Re: [PATCH 1/1 v7] usb: serial: add support for CH348

On Tue, May 07, 2024 at 01:15:22PM +0000, Corentin Labbe wrote:
> 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

Could you please include a pointer to the vendor driver (which I assumed
you based this on)?

> Signed-off-by: Corentin Labbe <clabbe@...libre.com>
> ---
>  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@...libre.com>

Do you need to include any copyrights from the vendor driver? It looks
like at least some of the code below was copied from somewhere (but
perhaps not that much).

> + * With the help of Neil Armstrong <neil.armstrong@...aro.org>
> + * and the help of Martin Blumenstingl <martin.blumenstingl@...glemail.com>
> + */
> +
> +#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

This look like standard IIR masks (e.g. R_II_B2 would be Transmit
holding register empty).

> +
> +#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

nit: lowercase L for consistency, but it's not really a list

> + * @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[];

This buffer should be allocated separately as it is used for DMA.

> +};
> +
> +struct ch348_magic {
> +	u8 action;
> +	u8 reg;
> +	u8 control;
> +} __packed;
> +
> +struct ch348_status_entry {
> +	u8 portnum:4;
> +	u8 unused:4;

Don't use bitfields for things that go over the wire.

> +	u8 reg_iir;
> +	union {
> +		u8 lsr_signal;
> +		u8 modem_signal;
> +		u8 init_data[10];

This init_data field is never used and looks a bit odd. What is it used
for?

You mentioned that that the modem lines are not yet used either.

> +	};
> +} __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;

Avoid mixing and multitple declarations and initialisation like this.
One declaration per line is usually preferred unless it's related stuff.

> +	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);

Please avoid __func__ in error messages and spell out what happens
instead (e.g. "nonzero status-urb status received: %d").

> +		goto exit;
> +	}
> +
> +	if (urb->actual_length < 3) {
> +		dev_warn(&ch348->udev->dev,
> +			 "Received too short status buffer with %u bytes\n",
> +			 urb->actual_length);

This needs to be ratelimited at a minimum.

> +		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);

Same here.

> +			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;

Ok, so this is the init data. What it is used for?

> +		} else if ((status_entry->reg_iir & 0x0f) == R_II_B1) {

Use a define for the mask.

> +			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)

Should you really count every framing error as a break? Looks like this
should have been CH348_LB.

> +				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);

Ratelimited.

> +		}
> +
> +		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",

As mentioned above, please use a unified format for error message
without __func__, for example:

	"failed to resubmit status urb: %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);

As above: "failed to write magic: %d\n"

> +
> +	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);

This looks like it could be a write to the standard Fifo Control
Register.

> +	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)

You don't hold the termios lock here so this needs to be handled
differently. Perhaps you can set a flag in set_termios if this is
really needed.

> +		/*
> +		 * 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;

Can you elaborate on you findings here? According to the vendor homepage
this device has a 1024 byte TX fifo per port. Are you really saying that
for some reason you can only fill it with 128 b when the line speed is
below 9600?

> +	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.

As I mentioned above R_II_B2 appears to be the transfer holding register
empty flag in IIR. So you write one endpoint size worth of data and then
wait for all of it to be processed on the device before sending more.

How big is the endpoint (please post lsusb -v)?

> +		* 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.

If the hardware really works this way, then perhaps you should not use
the generic write implementation. Just maintain a single urb per port
and don't submit it until the device fifo is empty.

> +		*/
> +		max_tx_size = port->bulk_out_size - CH348_TX_HDRSIZE;
> +
> +	reinit_completion(&ch348_port->write_completion);

This is broken as write can be called at any time and may clear any
previous completion.

> +
> +	mutex_lock(&ch348->write_lock);

Write should not be blocking. Just queue data in the fifo and start a
new transfer when the hardware allows you to.

> +
> +	/*
> +	 * 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);

You should update termios with the new rate.

> +
> +	format = termios->c_cflag & CSTOPB ? 2 : 1;

Please use defines for the constants.

> +
> +	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;
> +	}

Just spell this out all the cases instead of doing this constant
arithmetic and add defines for the parity modes.

> +
> +	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;

Eh, format is set to 1 or 2 above, and here you map this to 2 and 0 for
some reason. Use defines here too.

> +
> +	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);

drop err= in favour of : here and elsewhere.

> +		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);

"failed to configure: %d\n", and similar elsewhere

> +		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];

Odd variable name for the second port. I guess you really should be
using port[0] here.

> +	struct usb_device *usb_dev = serial->dev;
> +	int status_buffer_size, i, ret;

Don't mix declarations of unrelated variables like this.

> +	struct usb_interface *intf;
> +	struct ch348 *ch348;
> +
> +	intf = usb_ifnum_to_if(usb_dev, 0);

I assume you only have one interface and want to use serial->interface
here.

> +	epstatus = &intf->cur_altsetting->endpoint[2].desc;
> +	epcmd = &intf->cur_altsetting->endpoint[3].desc;

You need to make sure these endpoints exists as well (e.g. by setting
num_bulk_in/out in the driver data below).

> +
> +	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;

I know we have other driver submitting these at attach() but this really
should be done on first open to avoid wasting resources. I guess this is
ok for now.

> +
> +	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);

serial->interface

> +
> +	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;
> +	}

Not needed since you set num_bulk_in/out below (both should be 2 however).

> +	epstatus = &intf->cur_altsetting->endpoint[2].desc;

This could be accessing data beyond the endpoint array currently.

> +	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;
> +	}

And then can use just verify the status/cmd direction in attach().

Or you can use usb_check_bulk_endpoints() here.

> +
> +	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];

No need to set bulk_in[i], all reading is done via the first port.

> +	}
> +
> +	epds->num_bulk_out = CH348_MAXPORT;
> +	epds->num_bulk_in = CH348_MAXPORT;

And then only set num_bulk_out here.

> +
> +	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,

Set both of these to 2 so that core verifies that you have all four
endpoints.

> +	.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@...libre.com>");
> +MODULE_DESCRIPTION("USB CH348 Octo port serial converter driver");
> +MODULE_LICENSE("GPL");

Johan

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