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Message-Id: <20100907101835.a699ef6c.randy.dunlap@oracle.com>
Date: Tue, 7 Sep 2010 10:18:35 -0700
From: Randy Dunlap <randy.dunlap@...cle.com>
To: "Dr. Werner Fink" <werner@...e.de>
Cc: Greg KH <gregkh@...e.de>, Alan Cox <alan@...rguk.ukuu.org.uk>,
linux-kernel@...r.kernel.org, linux-api@...r.kernel.org
Subject: Re: [PATCH] tty: Add a new file /proc/tty/consoles
On Tue, 7 Sep 2010 18:53:05 +0200 Dr. Werner Fink wrote:
> Add a new file /proc/tty/consoles to be able to
> determine the registered system console lines.
> If the reading process holds /dev/console open at
> the regular standard input stream the active device
> will be marked by an asterisk.
>
> Signed-off-by: Werner Fink <werner@...e.de>
> ---
> Documentation/filesystems/proc.txt | 16 ++++
> fs/proc/proc_tty.c | 138 ++++++++++++++++++++++++++++++++++++
> 2 files changed, 154 insertions(+), 0 deletions(-)
>
> diff --git a/Documentation/filesystems/proc.txt b/Documentation/filesystems/proc.txt
> index 9fb6cbe..a5b6dd5 100644
> --- a/Documentation/filesystems/proc.txt
> +++ b/Documentation/filesystems/proc.txt
> @@ -1074,6 +1074,7 @@ Table 1-11: Files in /proc/tty
> drivers list of drivers and their usage
> ldiscs registered line disciplines
> driver/serial usage statistic and status of single tty lines
> + consoles registered system console lines
> ..............................................................................
>
> To see which tty's are currently in use, you can simply look into the file
> @@ -1092,6 +1093,21 @@ To see which tty's are currently in use, you can simply look into the file
> /dev/tty /dev/tty 5 0 system:/dev/tty
> unknown /dev/tty 4 1-63 console
>
> +To see which character device lines are currently used for the system console
> +/dev/console, you may simply look into the file /proc/tty/consoles:
> +
> + > cat /proc/tty/consoles
> + tty0 4:7
> + ttyS0 4:64
> +
> +If the reading process holds /dev/console open at the regular standard input
> +stream the active device will be marked by an asterisk:
> +
> + > cat /proc/tty/consoles < /dev/console
> + *tty0 4:7
> + > tty
> + /dev/pts/3
> +
>
> 1.8 Miscellaneous kernel statistics in /proc/stat
> -------------------------------------------------
> diff --git a/fs/proc/proc_tty.c b/fs/proc/proc_tty.c
> index 83adcc8..f717e84 100644
> --- a/fs/proc/proc_tty.c
> +++ b/fs/proc/proc_tty.c
> @@ -12,7 +12,10 @@
> #include <linux/proc_fs.h>
> #include <linux/stat.h>
> #include <linux/tty.h>
> +#include <linux/tty_driver.h>
> +#include <linux/console.h>
> #include <linux/seq_file.h>
> +#include <linux/fdtable.h>
> #include <linux/bitops.h>
>
> /*
> @@ -137,6 +140,140 @@ static const struct file_operations proc_tty_drivers_operations = {
> };
>
> /*
> + * The device ID of file descriptor 0 of the current reading
> + * task if a character device...
> + */
> +static dev_t current_dev;
> +
> +/*
> + * This is the handler for /proc/tty/consoles
> + */
> +static int show_console_dev(struct seq_file *m, void *v)
> +{
> + const struct tty_driver * driver;
*driver;
(no space between them, here and other places)
> + struct console * con;
> + int index, len;
> + dev_t dev;
> +
> + if (v == SEQ_START_TOKEN)
> + return 0;
> + con = (struct console *)v;
> + if (!con)
> + return 0;
> + driver = con->device(con, &index);
> + if (!driver)
> + return 0;
> +
> + dev = MKDEV(driver->major, driver->minor_start) + index;
> +
> + seq_printf(m, "%s%s%d%n", (current_dev == dev) ? "*" : "",
> + con->name, con->index, &len);
I would decode con->flags here (like I did in a similar 2006 patch).
http://www.xenotime.net/linux/patches/consoles-list.patch
(not kept up to date)
> + len = 19 - len;
> + if (len < 1)
> + len = 1;
> + seq_printf(m, "%*c%d:%d\n", len, ' ', MAJOR(dev), MINOR(dev));
> +
> + return 0;
> +}
> +
> +/* iterator for consoles */
> +static void *c_start(struct seq_file *m, loff_t *pos)
> +{
> + struct console * con;
> + loff_t off = 0;
> +
> + if (*pos == 0)
> + return SEQ_START_TOKEN;
> +
> + acquire_console_sem();
> + for (con = console_drivers; con; con = con->next) {
> + if (!con->device)
> + continue;
> + if (!con->write)
> + continue;
> + if ((con->flags & CON_ENABLED) == 0)
> + continue;
> + if (++off == *pos)
> + break;
> + }
> + release_console_sem();
> +
> + return con;
> +}
> +
> +static void *c_next(struct seq_file *m, void *v, loff_t *pos)
> +{
> + struct console * con;
> +
> + acquire_console_sem();
> + if (v == SEQ_START_TOKEN)
> + con = console_drivers;
> + else
> + con = ((struct console *)v)->next;
> + for (; con; con = con->next) {
> + if (!con->device)
> + continue;
> + if (!con->write)
> + continue;
> + if ((con->flags & CON_ENABLED) == 0)
> + continue;
> + ++*pos;
> + break;
> + }
> + release_console_sem();
> +
> + return con;
> +}
> +
> +static void c_stop(struct seq_file *m, void *v)
> +{
> +}
> +
> +static const struct seq_operations tty_consoles_op = {
> + .start = c_start,
> + .next = c_next,
> + .stop = c_stop,
> + .show = show_console_dev
> +};
> +
> +static int tty_consoles_open(struct inode *inode, struct file *file)
> +{
> + struct files_struct * curfiles;
> +
> + current_dev = 0;
> + curfiles = get_files_struct(current);
> + if (curfiles) {
> + const struct file * curfp;
> + spin_lock(&curfiles->file_lock);
> + curfp = fcheck_files(curfiles, 0);
> + if (curfp && curfp->private_data) {
> + const struct inode * inode;
> + dget(curfp->f_dentry);
> + inode = curfp->f_dentry->d_inode;
> + if (S_ISCHR(inode->i_mode)) {
> + struct tty_struct * tty;
> + tty = (struct tty_struct *)curfp->private_data;
> + if (tty && tty->magic == TTY_MAGIC) {
> + tty = tty_pair_get_tty(tty);
> + current_dev = tty_devnum(tty);
> + }
> + }
> + dput(curfp->f_dentry);
> + }
> + spin_unlock(&curfiles->file_lock);
> + put_files_struct(curfiles);
> + }
> + return seq_open(file, &tty_consoles_op);
> +}
> +
> +static const struct file_operations proc_tty_consoles_operations = {
> + .open = tty_consoles_open,
> + .read = seq_read,
> + .llseek = seq_lseek,
> + .release = seq_release,
> +};
> +
> +/*
> * This function is called by tty_register_driver() to handle
> * registering the driver's /proc handler into /proc/tty/driver/<foo>
> */
> @@ -186,4 +323,5 @@ void __init proc_tty_init(void)
> proc_tty_driver = proc_mkdir_mode("tty/driver", S_IRUSR|S_IXUSR, NULL);
> proc_create("tty/ldiscs", 0, NULL, &tty_ldiscs_proc_fops);
> proc_create("tty/drivers", 0, NULL, &proc_tty_drivers_operations);
> + proc_create("tty/consoles", 0, NULL, &proc_tty_consoles_operations);
> }
> --
---
~Randy
*** Remember to use Documentation/SubmitChecklist when testing your code ***
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