Patchwork [2,of,2] netconsole: add write-only tty driver

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Submitter Hollis Blanchard
Date Nov. 27, 2008, 9:11 p.m.
Message ID <1a5d52ff499998079f4b.1227820262@localhost.localdomain>
Download mbox | patch
Permalink /patch/11265/
State Changes Requested
Delegated to: David Miller
Headers show

Comments

Hollis Blanchard - Nov. 27, 2008, 9:11 p.m.
This allows userspace to output to netconsole via the /dev/console device,
which is very useful to see initscript output, for example. There is only one
netconsole TTY device, and TTY output goes to all receivers specified for
console output.

Input via /dev/console is still not implemented, however.

Signed-off-by: Hollis Blanchard <hollisb@us.ibm.com>

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Evgeniy Polyakov - Nov. 27, 2008, 9:47 p.m.
Hi.

Looks good. A short note below.

On Thu, Nov 27, 2008 at 03:11:02PM -0600, Hollis Blanchard (hollisb@us.ibm.com) wrote:
> +static int __init netconsole_tty_init(void)
> +{
> +	netconsole_tty_driver = alloc_tty_driver(1);
> +	if (!netconsole_tty_driver)
> +		return -ENOMEM;
> +
> +	netconsole_tty_driver->owner = THIS_MODULE;
> +	netconsole_tty_driver->driver_name = "netcon";
> +	netconsole_tty_driver->name = "netcon";
> +	netconsole_tty_driver->minor_start = 0;
> +	netconsole_tty_driver->type = TTY_DRIVER_TYPE_SYSTEM;
> +	netconsole_tty_driver->init_termios = tty_std_termios;
> +	netconsole_tty_driver->init_termios.c_cflag = B9600 | CS8 | CREAD | HUPCL;
> +	netconsole_tty_driver->init_termios.c_ispeed = 9600;
> +	netconsole_tty_driver->init_termios.c_ospeed = 9600;
> +	netconsole_tty_driver->flags = TTY_DRIVER_REAL_RAW;
> +	tty_set_operations(netconsole_tty_driver, &netconsole_tty_ops);
> +
> +	if (tty_register_driver(netconsole_tty_driver))
> +		printk(KERN_ERR "Couldn't register netconsole tty driver\n");
> +
> +	return 0;
> +}
> +device_initcall(netconsole_tty_init);

Would it be better called from init_netconsole()?
Hollis Blanchard - Nov. 28, 2008, 5:25 a.m.
On Thursday 27 November 2008 15:47:01 Evgeniy Polyakov wrote:
> Hi.
> 
> Looks good. A short note below.
> 
> On Thu, Nov 27, 2008 at 03:11:02PM -0600, Hollis Blanchard 
(hollisb@us.ibm.com) wrote:
> > +static int __init netconsole_tty_init(void)
> > +{
> > +	netconsole_tty_driver = alloc_tty_driver(1);
> > +	if (!netconsole_tty_driver)
> > +		return -ENOMEM;
> > +
> > +	netconsole_tty_driver->owner = THIS_MODULE;
> > +	netconsole_tty_driver->driver_name = "netcon";
> > +	netconsole_tty_driver->name = "netcon";
> > +	netconsole_tty_driver->minor_start = 0;
> > +	netconsole_tty_driver->type = TTY_DRIVER_TYPE_SYSTEM;
> > +	netconsole_tty_driver->init_termios = tty_std_termios;
> > +	netconsole_tty_driver->init_termios.c_cflag = B9600 | CS8 | CREAD | 
HUPCL;
> > +	netconsole_tty_driver->init_termios.c_ispeed = 9600;
> > +	netconsole_tty_driver->init_termios.c_ospeed = 9600;
> > +	netconsole_tty_driver->flags = TTY_DRIVER_REAL_RAW;
> > +	tty_set_operations(netconsole_tty_driver, &netconsole_tty_ops);
> > +
> > +	if (tty_register_driver(netconsole_tty_driver))
> > +		printk(KERN_ERR "Couldn't register netconsole tty driver\n");
> > +
> > +	return 0;
> > +}
> > +device_initcall(netconsole_tty_init);
> 
> Would it be better called from init_netconsole()?

Hmm, I don't remember what the ordering is here. "console_initcall", used with 
most other console-providing drivers, is done before alloc_tty_driver() can 
work. However, since init_netconsole() is a "module_initcall", I guess that 
should work. Well, it must, since init_netconsole() calls kzalloc() already...
Matt Mackall - Nov. 30, 2008, 5:28 p.m.
On Thu, 2008-11-27 at 15:11 -0600, Hollis Blanchard wrote:
> This allows userspace to output to netconsole via the /dev/console device,
> which is very useful to see initscript output, for example. There is only one
> netconsole TTY device, and TTY output goes to all receivers specified for
> console output.
> 
> Input via /dev/console is still not implemented, however.
> 
> Signed-off-by: Hollis Blanchard <hollisb@us.ibm.com>
> 
> diff --git a/drivers/net/netconsole.c b/drivers/net/netconsole.c
> --- a/drivers/net/netconsole.c
> +++ b/drivers/net/netconsole.c
> @@ -43,6 +43,7 @@
>  #include <linux/netpoll.h>
>  #include <linux/inet.h>
>  #include <linux/configfs.h>
> +#include <linux/tty.h>
>  
>  MODULE_AUTHOR("Maintainer: Matt Mackall <mpm@selenic.com>");
>  MODULE_DESCRIPTION("Console driver for network interfaces");
> @@ -98,6 +99,8 @@ struct netconsole_target {
>  	int			enabled;
>  	struct netpoll		np;
>  };
> +
> +static struct tty_driver *netconsole_tty_driver;
>  
>  #ifdef	CONFIG_NETCONSOLE_DYNAMIC
>  
> @@ -728,15 +731,74 @@ static void netconsole_write_msg(const c
>  	spin_unlock_irqrestore(&target_list_lock, flags);
>  }
>  
> +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)
> +{
> +	netconsole_write_msg(buf, count);
> +	return count;
> +}
> +
> +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,
> +	.write_room = netconsole_tty_write_room,
> +};
> +
> +static int __init netconsole_tty_init(void)
> +{
> +	netconsole_tty_driver = alloc_tty_driver(1);
> +	if (!netconsole_tty_driver)
> +		return -ENOMEM;
> +
> +	netconsole_tty_driver->owner = THIS_MODULE;
> +	netconsole_tty_driver->driver_name = "netcon";
> +	netconsole_tty_driver->name = "netcon";
> +	netconsole_tty_driver->minor_start = 0;
> +	netconsole_tty_driver->type = TTY_DRIVER_TYPE_SYSTEM;
> +	netconsole_tty_driver->init_termios = tty_std_termios;
> +	netconsole_tty_driver->init_termios.c_cflag = B9600 | CS8 | CREAD | HUPCL;
> +	netconsole_tty_driver->init_termios.c_ispeed = 9600;
> +	netconsole_tty_driver->init_termios.c_ospeed = 9600;
> +	netconsole_tty_driver->flags = TTY_DRIVER_REAL_RAW;
> +	tty_set_operations(netconsole_tty_driver, &netconsole_tty_ops);
> +
> +	if (tty_register_driver(netconsole_tty_driver))
> +		printk(KERN_ERR "Couldn't register netconsole tty driver\n");
> +
> +	return 0;
> +}
> +device_initcall(netconsole_tty_init);

I agree with Evgeniy that this should be merged into the existing init
function. Otherwise there's reader ambiguity about the ordering.
Otherwise this looks good.

Patch

diff --git a/drivers/net/netconsole.c b/drivers/net/netconsole.c
--- a/drivers/net/netconsole.c
+++ b/drivers/net/netconsole.c
@@ -43,6 +43,7 @@ 
 #include <linux/netpoll.h>
 #include <linux/inet.h>
 #include <linux/configfs.h>
+#include <linux/tty.h>
 
 MODULE_AUTHOR("Maintainer: Matt Mackall <mpm@selenic.com>");
 MODULE_DESCRIPTION("Console driver for network interfaces");
@@ -98,6 +99,8 @@  struct netconsole_target {
 	int			enabled;
 	struct netpoll		np;
 };
+
+static struct tty_driver *netconsole_tty_driver;
 
 #ifdef	CONFIG_NETCONSOLE_DYNAMIC
 
@@ -728,15 +731,74 @@  static void netconsole_write_msg(const c
 	spin_unlock_irqrestore(&target_list_lock, flags);
 }
 
+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)
+{
+	netconsole_write_msg(buf, count);
+	return count;
+}
+
+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,
+	.write_room = netconsole_tty_write_room,
+};
+
+static int __init netconsole_tty_init(void)
+{
+	netconsole_tty_driver = alloc_tty_driver(1);
+	if (!netconsole_tty_driver)
+		return -ENOMEM;
+
+	netconsole_tty_driver->owner = THIS_MODULE;
+	netconsole_tty_driver->driver_name = "netcon";
+	netconsole_tty_driver->name = "netcon";
+	netconsole_tty_driver->minor_start = 0;
+	netconsole_tty_driver->type = TTY_DRIVER_TYPE_SYSTEM;
+	netconsole_tty_driver->init_termios = tty_std_termios;
+	netconsole_tty_driver->init_termios.c_cflag = B9600 | CS8 | CREAD | HUPCL;
+	netconsole_tty_driver->init_termios.c_ispeed = 9600;
+	netconsole_tty_driver->init_termios.c_ospeed = 9600;
+	netconsole_tty_driver->flags = TTY_DRIVER_REAL_RAW;
+	tty_set_operations(netconsole_tty_driver, &netconsole_tty_ops);
+
+	if (tty_register_driver(netconsole_tty_driver))
+		printk(KERN_ERR "Couldn't register netconsole tty driver\n");
+
+	return 0;
+}
+device_initcall(netconsole_tty_init);
+
 static void netconsole_console_write(struct console *con, const char *msg, unsigned int len)
 {
 	netconsole_write_msg(msg, len);
+}
+
+static struct tty_driver *netconsole_console_device(struct console *console, int *index)
+{
+	*index = console->index;
+	return netconsole_tty_driver;
 }
 
 static struct console netconsole = {
 	.name	= "netcon",
 	.flags	= CON_ENABLED,
 	.write	= netconsole_console_write,
+	.device = netconsole_console_device,
 };
 
 static int __init init_netconsole(void)