linux-kernel - Re: [PATCHv3] tty: Set correct tty name in 'active' sysfs attribute

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Date:	Mon, 24 Feb 2014 15:58:09 +0100
From:	David Herrmann <dh.herrmann@...il.com>
To:	Hannes Reinecke <hare@...e.de>
Cc:	linux-kernel <linux-kernel@...r.kernel.org>,
	Ray Strode <halfline@...il.com>,
	Lennart Poettering <lennart@...ttering.net>,
	Kay Sievers <kay@...y.org>,
	Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
	Jiri Slaby <jslaby@...e.cz>, Werner Fink <werner@...e.de>
Subject: Re: [PATCHv3] tty: Set correct tty name in 'active' sysfs attribute

Hi

On Mon, Feb 24, 2014 at 3:50 PM, Hannes Reinecke <hare@...e.de> wrote:
> 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.
> But we need to take care for the virtual console to always display
> 'tty0' so as not to break existing programs.
>
> Cc: Lennart Poettering <lennart@...ttering.net>
> Cc: Kay Sievers <kay@...y.org>
> Cc: Greg Kroah-Hartman <gregkh@...uxfoundation.org>
> Cc: Jiri Slaby <jslaby@...e.cz>
> Signed-off-by: Werner Fink <werner@...e.de>
> Signed-off-by: Hannes Reinecke <hare@...e.de>
> ---
>  drivers/tty/tty_io.c | 24 ++++++++++++++++++------
>  1 file changed, 18 insertions(+), 6 deletions(-)
>
> diff --git a/drivers/tty/tty_io.c b/drivers/tty/tty_io.c
> index c74a00a..96eb462 100644
> --- a/drivers/tty/tty_io.c
> +++ b/drivers/tty/tty_io.c
> @@ -1271,12 +1271,13 @@ static void pty_line_name(struct tty_driver *driver, int index, char *p)
>   *
>   *     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 +3546,20 @@ static ssize_t show_cons_active(struct device *dev,
>                 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);
> +               /* Some programs rely on 'tty0' for console */
> +               if (driver && (index > 0 || driver->major != TTY_MAJOR)) {

As Ray mentioned in the previous discussion, this has to be
cs[i]->index instead of "index" as ->device() changes the parameter.
See drivers/tty/vt/vt.c vt_console_device().

Thanks
David

> +                       count += tty_line_name(driver, index, buf + count);
> +                       count += sprintf(buf + count, "%c", i ? ' ':'\n');
> +               } else
> +                       count += sprintf(buf + count, "%s%d%c",
> +                                        name, cs[i]->index, i ? ' ':'\n');
> +       }
>         console_unlock();
>
>         return count;
> --
> 1.7.12.4
>
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