linux-kernel - Re: [PATCH 3.13 35/99] tty: Set correct tty name in active sysfs attribute

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Date:	Fri, 21 Feb 2014 09:48:46 -0500
From:	Josh Boyer <jwboyer@...oraproject.org>
To:	Greg Kroah-Hartman <gregkh@...uxfoundation.org>
Cc:	"Linux-Kernel@...r. Kernel. Org" <linux-kernel@...r.kernel.org>,
	"stable@...r.kernel.org" <stable@...r.kernel.org>,
	Lennart Poettering <lennart@...ttering.net>,
	Kay Sievers <kay@...y.org>, Jiri Slaby <jslaby@...e.cz>,
	David Herrmann <dh.herrmann@...il.com>,
	Werner Fink <werner@...e.de>, Hannes Reinecke <hare@...e.de>,
	Ray Strode <halfline@...il.com>
Subject: Re: [PATCH 3.13 35/99] tty: Set correct tty name in active sysfs attribute

On Thu, Feb 20, 2014 at 6:52 PM, Greg Kroah-Hartman
<gregkh@...uxfoundation.org> wrote:
> 3.13-stable review patch.  If anyone has any objections, please let me know.
>
> ------------------
>
> From: Hannes Reinecke <hare@...e.de>
>
> commit d8a5dc3033af2fd6d16030d2ee4fbd073460fe54 upstream.
>
> The 'active' sysfs attribute should refer to the currently active tty
> devices the console is running on, not the currently active console.
>
> The console structure doesn't refer to any device in sysfs, only the tty
> the console is running on has.  So we need to print out the tty names in
> 'active', not the console names.
>
> This resolves an issue on s390 platforms in determining the correct
> console device to use.

Just to be double sure this is seen, Ray points out that it breaks
current plymouth because the heuristic changed.  Hold off on this one?

josh

>
> Cc: Lennart Poettering <lennart@...ttering.net>
> Cc: Kay Sievers <kay@...y.org>
> Cc: Jiri Slaby <jslaby@...e.cz>
> Cc: David Herrmann <dh.herrmann@...il.com>
> Signed-off-by: Werner Fink <werner@...e.de>
> Signed-off-by: Hannes Reinecke <hare@...e.de>
> Signed-off-by: Greg Kroah-Hartman <gregkh@...uxfoundation.org>
>
> ---
>  Documentation/ABI/testing/sysfs-tty |    3 ++-
>  drivers/tty/tty_io.c                |   25 ++++++++++++++++++-------
>  2 files changed, 20 insertions(+), 8 deletions(-)
>
> --- a/Documentation/ABI/testing/sysfs-tty
> +++ b/Documentation/ABI/testing/sysfs-tty
> @@ -3,7 +3,8 @@ Date:           Nov 2010
>  Contact:       Kay Sievers <kay.sievers@...y.org>
>  Description:
>                  Shows the list of currently configured
> -                console devices, like 'tty1 ttyS0'.
> +                tty devices used for the console,
> +                like 'tty1 ttyS0'.
>                  The last entry in the file is the active
>                  device connected to /dev/console.
>                  The file supports poll() to detect virtual
> --- a/drivers/tty/tty_io.c
> +++ b/drivers/tty/tty_io.c
> @@ -1267,16 +1267,17 @@ static void pty_line_name(struct tty_dri
>   *     @p: output buffer of at least 7 bytes
>   *
>   *     Generate a name from a driver reference and write it to the output
> - *     buffer.
> + *     buffer. Return the number of bytes written.
>   *
>   *     Locking: None
>   */
> -static void tty_line_name(struct tty_driver *driver, int index, char *p)
> +static ssize_t tty_line_name(struct tty_driver *driver, int index, char *p)
>  {
>         if (driver->flags & TTY_DRIVER_UNNUMBERED_NODE)
> -               strcpy(p, driver->name);
> +               return sprintf(p, "%s", driver->name);
>         else
> -               sprintf(p, "%s%d", driver->name, index + driver->name_base);
> +               return sprintf(p, "%s%d", driver->name,
> +                              index + driver->name_base);
>  }
>
>  /**
> @@ -3545,9 +3546,19 @@ static ssize_t show_cons_active(struct d
>                 if (i >= ARRAY_SIZE(cs))
>                         break;
>         }
> -       while (i--)
> -               count += sprintf(buf + count, "%s%d%c",
> -                                cs[i]->name, cs[i]->index, i ? ' ':'\n');
> +       while (i--) {
> +               struct tty_driver *driver;
> +               const char *name = cs[i]->name;
> +               int index = cs[i]->index;
> +
> +               driver = cs[i]->device(cs[i], &index);
> +               if (driver) {
> +                       count += tty_line_name(driver, index, buf + count);
> +                       count += sprintf(buf + count, "%c", i ? ' ':'\n');
> +               } else
> +                       count += sprintf(buf + count, "%s%d%c",
> +                                        name, index, i ? ' ':'\n');
> +       }
>         console_unlock();
>
>         return count;
>
>
> --
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