// SPDX-License-Identifier: GPL-2.0
/*
 * USB Serial Console driver
 *
 * Copyright (C) 2001 - 2002 Greg Kroah-Hartman (greg@kroah.com)
 *
 * Thanks to Randy Dunlap for the original version of this code.
 *
 */

#define pr_fmt(fmt) KBUILD_MODNAME ": " fmt

#include <linux/kernel.h>
#include <linux/module.h>
#include <linux/slab.h>
#include <linux/tty.h>
#include <linux/console.h>
#include <linux/serial.h>
#include <linux/usb.h>
#include <linux/usb/serial.h>

struct usbcons_info {
        int                     magic;
        int                     break_flag;
        struct usb_serial_port  *port;
};

static struct usbcons_info usbcons_info;
static struct console usbcons;

/*
 * ------------------------------------------------------------
 * USB Serial console driver
 *
 * Much of the code here is copied from drivers/char/serial.c
 * and implements a phony serial console in the same way that
 * serial.c does so that in case some software queries it,
 * it will get the same results.
 *
 * Things that are different from the way the serial port code
 * does things, is that we call the lower level usb-serial
 * driver code to initialize the device, and we set the initial
 * console speeds based on the command line arguments.
 * ------------------------------------------------------------
 */

static const struct tty_operations usb_console_fake_tty_ops = {
};

/*
 * The parsing of the command line works exactly like the
 * serial.c code, except that the specifier is "ttyUSB" instead
 * of "ttyS".
 */
static int usb_console_setup(struct console *co, char *options)
{
        struct usbcons_info *info = &usbcons_info;
        int baud = 9600;
        int bits = 8;
        int parity = 'n';
        int doflow = 0;
        int cflag = CREAD | HUPCL | CLOCAL;
        char *s;
        struct usb_serial *serial;
        struct usb_serial_port *port;
        int retval;
        struct tty_struct *tty = NULL;
        struct ktermios dummy;

        if (options) {
                baud = simple_strtoul(options, NULL, 10);
                s = options;
                while (*s >= '0' && *s <= '9')
                        s++;
                if (*s)
                        parity = *s++;
                if (*s)
                        bits   = *s++ - '0';
                if (*s)
                        doflow = (*s++ == 'r');
        }
        
        /* Sane default */
        if (baud == 0)
                baud = 9600;

        switch (bits) {
        case 7:
                cflag |= CS7;
                break;
        default:
        case 8:
                cflag |= CS8;
                break;
        }
        switch (parity) {
        case 'o': case 'O':
                cflag |= PARODD;
                break;
        case 'e': case 'E':
                cflag |= PARENB;
                break;
        }

        /*
         * no need to check the index here: if the index is wrong, console
         * code won't call us
         */
        port = usb_serial_port_get_by_minor(co->index);
        if (port == NULL) {
                /* no device is connected yet, sorry :( */
                pr_err("No USB device connected to ttyUSB%i\n", co->index);
                return -ENODEV;
        }
        serial = port->serial;

        retval = usb_autopm_get_interface(serial->interface);
        if (retval)
                goto error_get_interface;

        tty_port_tty_set(&port->port, NULL);

        info->port = port;

        ++port->port.count;
        if (!tty_port_initialized(&port->port)) {
                if (serial->type->set_termios) {
                        /*
                         * allocate a fake tty so the driver can initialize
                         * the termios structure, then later call set_termios to
                         * configure according to command line arguments
                         */
                        tty = kzalloc(sizeof(*tty), GFP_KERNEL);
                        if (!tty) {
                                retval = -ENOMEM;
                                goto reset_open_count;
                        }
                        kref_init(&tty->kref);
                        tty->driver = usb_serial_tty_driver;
                        tty->index = co->index;
                        init_ldsem(&tty->ldisc_sem);
                        spin_lock_init(&tty->files_lock);
                        INIT_LIST_HEAD(&tty->tty_files);
                        kref_get(&tty->driver->kref);
                        __module_get(tty->driver->owner);
                        tty->ops = &usb_console_fake_tty_ops;
                        tty_init_termios(tty);
                        tty_port_tty_set(&port->port, tty);
                }

                /* only call the device specific open if this
                 * is the first time the port is opened */
                retval = serial->type->open(NULL, port);
                if (retval) {
                        dev_err(&port->dev, "could not open USB console port\n");
                        goto fail;
                }

                if (serial->type->set_termios) {
                        tty->termios.c_cflag = cflag;
                        tty_termios_encode_baud_rate(&tty->termios, baud, baud);
                        memset(&dummy, 0, sizeof(struct ktermios));
                        serial->type->set_termios(tty, port, &dummy);

                        tty_port_tty_set(&port->port, NULL);
                        tty_save_termios(tty);
                        tty_kref_put(tty);
                }
                tty_port_set_initialized(&port->port, 1);
        }
        /* Now that any required fake tty operations are completed restore
         * the tty port count */
        --port->port.count;
        /* The console is special in terms of closing the device so
         * indicate this port is now acting as a system console. */
        port->port.console = 1;

        mutex_unlock(&serial->disc_mutex);
        return retval;

 fail:
        tty_port_tty_set(&port->port, NULL);
        tty_kref_put(tty);
 reset_open_count:
        port->port.count = 0;
        info->port = NULL;
        usb_autopm_put_interface(serial->interface);
 error_get_interface:
        usb_serial_put(serial);
        mutex_unlock(&serial->disc_mutex);
        return retval;
}

static void usb_console_write(struct console *co,
                                        const char *buf, unsigned count)
{
        static struct usbcons_info *info = &usbcons_info;
        struct usb_serial_port *port = info->port;
        struct usb_serial *serial;
        int retval = -ENODEV;

        if (!port || port->serial->dev->state == USB_STATE_NOTATTACHED)
                return;
        serial = port->serial;

        if (count == 0)
                return;

        dev_dbg(&port->dev, "%s - %d byte(s)\n", __func__, count);

        if (!port->port.console) {
                dev_dbg(&port->dev, "%s - port not opened\n", __func__);
                return;
        }

        while (count) {
                unsigned int i;
                unsigned int lf;
                /* search for LF so we can insert CR if necessary */
                for (i = 0, lf = 0 ; i < count ; i++) {
                        if (*(buf + i) == 10) {
                                lf = 1;
                                i++;
                                break;
                        }
                }
                /* pass on to the driver specific version of this function if
                   it is available */
                retval = serial->type->write(NULL, port, buf, i);
                dev_dbg(&port->dev, "%s - write: %d\n", __func__, retval);
                if (lf) {
                        /* append CR after LF */
                        unsigned char cr = 13;
                        retval = serial->type->write(NULL, port, &cr, 1);
                        dev_dbg(&port->dev, "%s - write cr: %d\n",
                                                        __func__, retval);
                }
                buf += i;
                count -= i;
        }
}

static struct tty_driver *usb_console_device(struct console *co, int *index)
{
        struct tty_driver **p = (struct tty_driver **)co->data;

        if (!*p)
                return NULL;

        *index = co->index;
        return *p;
}

static struct console usbcons = {
        .name =         "ttyUSB",
        .write =        usb_console_write,
        .device =       usb_console_device,
        .setup =        usb_console_setup,
        .flags =        CON_PRINTBUFFER,
        .index =        -1,
        .data =         &usb_serial_tty_driver,
};

void usb_serial_console_disconnect(struct usb_serial *serial)
{
        if (serial->port[0] && serial->port[0] == usbcons_info.port) {
                usb_serial_console_exit();
                usb_serial_put(serial);
        }
}

void usb_serial_console_init(int minor)
{
        if (minor == 0) {
                /*
                 * Call register_console() if this is the first device plugged
                 * in.  If we call it earlier, then the callback to
                 * console_setup() will fail, as there is not a device seen by
                 * the USB subsystem yet.
                 */
                /*
                 * Register console.
                 * NOTES:
                 * console_setup() is called (back) immediately (from
                 * register_console). console_write() is called immediately
                 * from register_console iff CON_PRINTBUFFER is set in flags.
                 */
                pr_debug("registering the USB serial console.\n");
                register_console(&usbcons);
        }
}

void usb_serial_console_exit(void)
{
        if (usbcons_info.port) {
                unregister_console(&usbcons);
                usbcons_info.port->port.console = 0;
                usbcons_info.port = NULL;
        }
}