v4.19.13 snapshot.
diff --git a/drivers/usb/serial/console.c b/drivers/usb/serial/console.c
new file mode 100644
index 0000000..7d28930
--- /dev/null
+++ b/drivers/usb/serial/console.c
@@ -0,0 +1,301 @@
+// 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;
+ }
+}
+