Date:	Tue, 1 Apr 2014 23:13:06 +0200
From:	Struan Bartlett <struan.bartlett@...il.com>
To:	Matt Mackall <mpm@...enic.com>
Cc:	linux-kernel@...r.kernel.org,
	Andreas Schwab <schwab@...ux-m68k.org>, netdev@...r.kernel.org,
	"David S. Miller" <davem@...emloft.net>,
	Nikolay Aleksandrov <nikolay@...hat.com>,
	Andy Shevchenko <andy.shevchenko@...il.com>,
	Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
	Jiri Pirko <jiri@...nulli.us>, Joe Perches <joe@...ches.com>,
	Dan Aloni <alonid@...tram.com>
Subject: [PATCH v1] netconsole: Add tty driver

Adds tty driver to netconsole module. When module is loaded, it
creates /dev/netcon0 device and enables support for console=netcon0
kernel cmdline option, causing /dev/console output to be sent to
/dev/netcon0. This allows startup/shutdown script output from
headless platforms to be logged over (secure) network.

Signed-off-by: Struan Bartlett <struan.bartlett@...il.com>
---

--- a/drivers/net/netconsole.c  2014-03-31 04:40:15.000000000 +0100
+++ b/drivers/net/netconsole.c  2014-04-01 11:58:50.000000000 +0100
@@ -15,6 +15,7 @@
  *               generic card hooks
  *               works non-modular
  * 2003-09-07    rewritten with netpoll api
+ * 2014-03-31    tty driver by Struan Bartlett
  */

 /****************************************************************
@@ -47,6 +48,7 @@
 #include <linux/netpoll.h>
 #include <linux/inet.h>
 #include <linux/configfs.h>
+#include <linux/tty.h>

 MODULE_AUTHOR("Maintainer: Matt Mackall <mpm@...enic.com>");
 MODULE_DESCRIPTION("Console driver for network interfaces");
@@ -728,7 +730,7 @@ static struct notifier_block netconsole_
        .notifier_call  = netconsole_netdev_event,
 };

-static void write_msg(struct console *con, const char *msg, unsigned int len)
+static void _write_msg(const char *msg, unsigned int len)
 {
        int frag, left;
        unsigned long flags;
@@ -764,10 +766,63 @@ static void write_msg(struct console *co
        spin_unlock_irqrestore(&target_list_lock, flags);
 }

+static void write_msg(struct console *con, const char *msg, unsigned int len)
+{
+       _write_msg(msg, len);
+}
+
+static int netconsole_tty_open(struct tty_struct *tty, struct file *filp)
+{
+       return 0;
+}
+
+static void netconsole_tty_close(struct tty_struct *tty, struct file *filp)
+{
+}
+
+static int netconsole_tty_write(struct tty_struct *tty,
+                               const unsigned char *buf, int count)
+{
+       _write_msg(buf, count);
+       return count;
+}
+
+static int netconsole_tty_put_char(struct tty_struct *tty, unsigned char ch)
+{
+       char temp[2] = { ch, 0 };
+       _write_msg(temp, 1);
+       return 1;
+}
+
+static int netconsole_tty_write_room(struct tty_struct *tty)
+{
+       return MAX_PRINT_CHUNK;
+}
+
+static const struct tty_operations netconsole_tty_ops = {
+       .open           = netconsole_tty_open,
+       .close          = netconsole_tty_close,
+       .write          = netconsole_tty_write,
+       .put_char       = netconsole_tty_put_char,
+       .write_room     = netconsole_tty_write_room,
+};
+
+static struct tty_port netconsole_tty_port;
+static struct tty_driver *netconsole_tty_driver;
+
+static struct tty_driver *netconsole_device(struct console *co, int *index)
+{
+       if (!(co->flags & CON_ENABLED))
+               return NULL;
+       *index = co->index;
+       return netconsole_tty_driver;
+}
+
 static struct console netconsole = {
        .name   = "netcon",
        .flags  = CON_ENABLED,
        .write  = write_msg,
+       .device = netconsole_device
 };

 static int __init init_netconsole(void)
@@ -802,11 +857,39 @@ static int __init init_netconsole(void)
        if (err)
                goto undonotifier;

+       netconsole_tty_driver = alloc_tty_driver(1);
+       if (!netconsole_tty_driver) {
+               err = -ENOMEM;
+               goto undonotifier;
+       }
+
+       tty_port_init(&netconsole_tty_port);
+
+       netconsole_tty_driver->driver_name = "netcon";
+       netconsole_tty_driver->name = "netcon";
+       netconsole_tty_driver->type = TTY_DRIVER_TYPE_SYSTEM;
+       netconsole_tty_driver->subtype = SYSTEM_TYPE_TTY;
+       netconsole_tty_driver->init_termios = tty_std_termios;
+       netconsole_tty_driver->init_termios.c_iflag = 0;
+       netconsole_tty_driver->init_termios.c_oflag = 0;
+       netconsole_tty_driver->flags = TTY_DRIVER_REAL_RAW;
+
+       tty_set_operations(netconsole_tty_driver, &netconsole_tty_ops);
+       tty_port_link_device(&netconsole_tty_port, netconsole_tty_driver, 0);
+
+       err = tty_register_driver(netconsole_tty_driver);
+       if (err)
+               goto undotty;
+
        register_console(&netconsole);
        pr_info("network logging started\n");

        return err;

+undotty:
+       put_tty_driver(netconsole_tty_driver);
+       tty_port_destroy(&netconsole_tty_port);
+
 undonotifier:
        unregister_netdevice_notifier(&netconsole_netdev_notifier);

@@ -830,6 +913,10 @@ static void __exit cleanup_netconsole(vo
 {
        struct netconsole_target *nt, *tmp;

+       tty_unregister_driver(netconsole_tty_driver);
+       put_tty_driver(netconsole_tty_driver);
+       tty_port_destroy(&netconsole_tty_port);
+
        unregister_console(&netconsole);
        dynamic_netconsole_exit();
        unregister_netdevice_notifier(&netconsole_netdev_notifier);
--
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