usb/serial/console.c

0001 // SPDX-License-Identifier: GPL-2.0
0002 /*
0003  * USB Serial Console driver
0004  *
0005  * Copyright (C) 2001 - 2002 Greg Kroah-Hartman (greg@kroah.com)
0006  *
0007  * Thanks to Randy Dunlap for the original version of this code.
0008  *
0009  */
0010
0011 #define pr_fmt(fmt) KBUILD_MODNAME ": " fmt
0012
0013 #include <linux/kernel.h>
0014 #include <linux/module.h>
0015 #include <linux/slab.h>
0016 #include <linux/tty.h>
0017 #include <linux/console.h>
0018 #include <linux/serial.h>
0019 #include <linux/usb.h>
0020 #include <linux/usb/serial.h>
0021
0022 struct usbcons_info {
0023     int         magic;
0024     int         break_flag;
0025     struct usb_serial_port  *port;
0026 };
0027
0028 static struct usbcons_info usbcons_info;
0029 static struct console usbcons;
0030
0031 /*
0032  * ------------------------------------------------------------
0033  * USB Serial console driver
0034  *
0035  * Much of the code here is copied from drivers/char/serial.c
0036  * and implements a phony serial console in the same way that
0037  * serial.c does so that in case some software queries it,
0038  * it will get the same results.
0039  *
0040  * Things that are different from the way the serial port code
0041  * does things, is that we call the lower level usb-serial
0042  * driver code to initialize the device, and we set the initial
0043  * console speeds based on the command line arguments.
0044  * ------------------------------------------------------------
0045  */
0046
0047 static const struct tty_operations usb_console_fake_tty_ops = {
0048 };
0049
0050 /*
0051  * The parsing of the command line works exactly like the
0052  * serial.c code, except that the specifier is "ttyUSB" instead
0053  * of "ttyS".
0054  */
0055 static int usb_console_setup(struct console *co, char *options)
0056 {
0057     struct usbcons_info *info = &usbcons_info;
0058     int baud = 9600;
0059     int bits = 8;
0060     int parity = 'n';
0061     int doflow = 0;
0062     int cflag = CREAD | HUPCL | CLOCAL;
0063     char *s;
0064     struct usb_serial *serial;
0065     struct usb_serial_port *port;
0066     int retval;
0067     struct tty_struct *tty = NULL;
0068     struct ktermios dummy;
0069
0070     if (options) {
0071         baud = simple_strtoul(options, NULL, 10);
0072         s = options;
0073         while (*s >= '0' && *s <= '9')
0074             s++;
0075         if (*s)
0076             parity = *s++;
0077         if (*s)
0078             bits   = *s++ - '0';
0079         if (*s)
0080             doflow = (*s++ == 'r');
0081     }
0082
0083     /* Sane default */
0084     if (baud == 0)
0085         baud = 9600;
0086
0087     switch (bits) {
0088     case 7:
0089         cflag |= CS7;
0090         break;
0091     default:
0092     case 8:
0093         cflag |= CS8;
0094         break;
0095     }
0096     switch (parity) {
0097     case 'o': case 'O':
0098         cflag |= PARODD;
0099         break;
0100     case 'e': case 'E':
0101         cflag |= PARENB;
0102         break;
0103     }
0104
0105     if (doflow)
0106         cflag |= CRTSCTS;
0107
0108     /*
0109      * no need to check the index here: if the index is wrong, console
0110      * code won't call us
0111      */
0112     port = usb_serial_port_get_by_minor(co->index);
0113     if (port == NULL) {
0114         /* no device is connected yet, sorry :( */
0115         pr_err("No USB device connected to ttyUSB%i\n", co->index);
0116         return -ENODEV;
0117     }
0118     serial = port->serial;
0119
0120     retval = usb_autopm_get_interface(serial->interface);
0121     if (retval)
0122         goto error_get_interface;
0123
0124     tty_port_tty_set(&port->port, NULL);
0125
0126     info->port = port;
0127
0128     ++port->port.count;
0129     if (!tty_port_initialized(&port->port)) {
0130         if (serial->type->set_termios) {
0131             /*
0132              * allocate a fake tty so the driver can initialize
0133              * the termios structure, then later call set_termios to
0134              * configure according to command line arguments
0135              */
0136             tty = kzalloc(sizeof(*tty), GFP_KERNEL);
0137             if (!tty) {
0138                 retval = -ENOMEM;
0139                 goto reset_open_count;
0140             }
0141             kref_init(&tty->kref);
0142             tty->driver = usb_serial_tty_driver;
0143             tty->index = co->index;
0144             init_ldsem(&tty->ldisc_sem);
0145             spin_lock_init(&tty->files_lock);
0146             INIT_LIST_HEAD(&tty->tty_files);
0147             kref_get(&tty->driver->kref);
0148             __module_get(tty->driver->owner);
0149             tty->ops = &usb_console_fake_tty_ops;
0150             tty_init_termios(tty);
0151             tty_port_tty_set(&port->port, tty);
0152         }
0153
0154         /* only call the device specific open if this
0155          * is the first time the port is opened */
0156         retval = serial->type->open(NULL, port);
0157         if (retval) {
0158             dev_err(&port->dev, "could not open USB console port\n");
0159             goto fail;
0160         }
0161
0162         if (serial->type->set_termios) {
0163             tty->termios.c_cflag = cflag;
0164             tty_termios_encode_baud_rate(&tty->termios, baud, baud);
0165             memset(&dummy, 0, sizeof(struct ktermios));
0166             serial->type->set_termios(tty, port, &dummy);
0167
0168             tty_port_tty_set(&port->port, NULL);
0169             tty_save_termios(tty);
0170             tty_kref_put(tty);
0171         }
0172         tty_port_set_initialized(&port->port, 1);
0173     }
0174     /* Now that any required fake tty operations are completed restore
0175      * the tty port count */
0176     --port->port.count;
0177     /* The console is special in terms of closing the device so
0178      * indicate this port is now acting as a system console. */
0179     port->port.console = 1;
0180
0181     mutex_unlock(&serial->disc_mutex);
0182     return retval;
0183
0184  fail:
0185     tty_port_tty_set(&port->port, NULL);
0186     tty_kref_put(tty);
0187  reset_open_count:
0188     port->port.count = 0;
0189     info->port = NULL;
0190     usb_autopm_put_interface(serial->interface);
0191  error_get_interface:
0192     usb_serial_put(serial);
0193     mutex_unlock(&serial->disc_mutex);
0194     return retval;
0195 }
0196
0197 static void usb_console_write(struct console *co,
0198                     const char *buf, unsigned count)
0199 {
0200     static struct usbcons_info *info = &usbcons_info;
0201     struct usb_serial_port *port = info->port;
0202     struct usb_serial *serial;
0203     int retval = -ENODEV;
0204
0205     if (!port || port->serial->dev->state == USB_STATE_NOTATTACHED)
0206         return;
0207     serial = port->serial;
0208
0209     if (count == 0)
0210         return;
0211
0212     dev_dbg(&port->dev, "%s - %d byte(s)\n", __func__, count);
0213
0214     if (!port->port.console) {
0215         dev_dbg(&port->dev, "%s - port not opened\n", __func__);
0216         return;
0217     }
0218
0219     while (count) {
0220         unsigned int i;
0221         unsigned int lf;
0222         /* search for LF so we can insert CR if necessary */
0223         for (i = 0, lf = 0 ; i < count ; i++) {
0224             if (*(buf + i) == 10) {
0225                 lf = 1;
0226                 i++;
0227                 break;
0228             }
0229         }
0230         /* pass on to the driver specific version of this function if
0231            it is available */
0232         retval = serial->type->write(NULL, port, buf, i);
0233         dev_dbg(&port->dev, "%s - write: %d\n", __func__, retval);
0234         if (lf) {
0235             /* append CR after LF */
0236             unsigned char cr = 13;
0237             retval = serial->type->write(NULL, port, &cr, 1);
0238             dev_dbg(&port->dev, "%s - write cr: %d\n",
0239                             __func__, retval);
0240         }
0241         buf += i;
0242         count -= i;
0243     }
0244 }
0245
0246 static struct tty_driver *usb_console_device(struct console *co, int *index)
0247 {
0248     struct tty_driver **p = (struct tty_driver **)co->data;
0249
0250     if (!*p)
0251         return NULL;
0252
0253     *index = co->index;
0254     return *p;
0255 }
0256
0257 static struct console usbcons = {
0258     .name =     "ttyUSB",
0259     .write =    usb_console_write,
0260     .device =   usb_console_device,
0261     .setup =    usb_console_setup,
0262     .flags =    CON_PRINTBUFFER,
0263     .index =    -1,
0264     .data =     &usb_serial_tty_driver,
0265 };
0266
0267 void usb_serial_console_disconnect(struct usb_serial *serial)
0268 {
0269     if (serial->port[0] && serial->port[0] == usbcons_info.port) {
0270         usb_serial_console_exit();
0271         usb_serial_put(serial);
0272     }
0273 }
0274
0275 void usb_serial_console_init(int minor)
0276 {
0277     if (minor == 0) {
0278         /*
0279          * Call register_console() if this is the first device plugged
0280          * in.  If we call it earlier, then the callback to
0281          * console_setup() will fail, as there is not a device seen by
0282          * the USB subsystem yet.
0283          */
0284         /*
0285          * Register console.
0286          * NOTES:
0287          * console_setup() is called (back) immediately (from
0288          * register_console). console_write() is called immediately
0289          * from register_console iff CON_PRINTBUFFER is set in flags.
0290          */
0291         pr_debug("registering the USB serial console.\n");
0292         register_console(&usbcons);
0293     }
0294 }
0295
0296 void usb_serial_console_exit(void)
0297 {
0298     if (usbcons_info.port) {
0299         unregister_console(&usbcons);
0300         usbcons_info.port->port.console = 0;
0301         usbcons_info.port = NULL;
0302     }
0303 }
0304