console.c

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/*
 * USB Serial Console driver
 *
 * Copyright (C) 2001 - 2002 Greg Kroah-Hartman ([email protected])
 *
 *  This program is free software; you can redistribute it and/or
 *  modify it under the terms of the GNU General Public License version
 *  2 as published by the Free Software Foundation.
 *
 * Thanks to Randy Dunlap for the original version of this code.
 *
 */

#define pr_fmt(fmt) KBUILD_MODNAME ": " fmt

#include <linux/kernel.h>
#include <linux/init.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.
 * ------------------------------------------------------------
 */


/*
 * 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;
    }
    co->cflag = cflag;

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

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

    port = serial->port[co->index - serial->minor];
    tty_port_tty_set(&port->port, NULL);

    info->port = port;

    ++port->port.count;
    if (!test_bit(ASYNCB_INITIALIZED, &port->port.flags)) {
        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;
                dev_err(&port->dev, "no more memory\n");
                goto reset_open_count;
            }
            kref_init(&tty->kref);
            tty_port_tty_set(&port->port, tty);
            tty->driver = usb_serial_tty_driver;
            tty->index = co->index;
            if (tty_init_termios(tty)) {
                retval = -ENOMEM;
                dev_err(&port->dev, "no more memory\n");
                goto free_tty;
            }
        }

        /* only call the device specific open if this
         * is the first time the port is opened */
        if (serial->type->open)
            retval = serial->type->open(NULL, port);
        else
            retval = usb_serial_generic_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);
            kfree(tty);
        }
        set_bit(ASYNCB_INITIALIZED, &port->port.flags);
    }
    /* 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);
 free_tty:
    kfree(tty);
 reset_open_count:
    port->port.count = 0;
    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;

    pr_debug("%s - port %d, %d byte(s)\n", __func__, port->number, count);

    if (!port->port.console) {
        pr_debug("%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 */
        if (serial->type->write)
            retval = serial->type->write(NULL, port, buf, i);
        else
            retval = usb_serial_generic_write(NULL, port, buf, i);
        pr_debug("%s - return value : %d\n", __func__, retval);
        if (lf) {
            /* append CR after LF */
            unsigned char cr = 13;
            if (serial->type->write)
                retval = serial->type->write(NULL,
                                port, &cr, 1);
            else
                retval = usb_serial_generic_write(NULL,
                                port, &cr, 1);
            pr_debug("%s - return value : %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 && serial->port && 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;
    }
}