lkml.org 
[lkml]   [2009]   [Sep]   [8]   [last100]   RSS Feed
Views: [wrap][no wrap]   [headers]  [forward] 
 
Messages in this thread
    Patch in this message
    /
    Date
    From
    Subject[PATCH RFC] char/tty_io: fix legacy pty name when more than 256 pty devices are requested
    There are some use cases where more than 256 pty device pairs are needed.

    With kernel 2.6, the number of minors is not 256 anymore. So, it is
    possible to have more than 256 pty devices, either by specifying the number
    of tty devices at CONFIG_LEGACY_PTY_COUNT or by using tty.legacy_count parameter
    at boot time.

    However, the pty_line_name() only provides device names for the first
    256 tty/pty devices.

    As this function is used to generate the sysfs class name, any number of
    pty devices above 256 will fail to properly register them at sysfs.

    This is a bug, since there's no limits for the maximum number of legacy
    pty devices at Kconfig or at pty.legacy_count.

    It is important to preserve the old nomenclature for tty/pty devices for the
    first 256 devices, to avoid breakage on existing applications and with udev.

    So, in order to allow more pty devices, the nomenclature were extended for
    the devices with minor 256 or above. For those, the nomenclature will be:
    ttyf0000-ttfpffff (pty slave)
    ptyf0000-ttyfffff (pty master)

    Signed-off-by: Mauro Carvalho Chehab <mchehab@redhat.com>

    diff --git a/drivers/char/tty_io.c b/drivers/char/tty_io.c
    index a3afa0c..fdea89b 100644
    --- a/drivers/char/tty_io.c
    +++ b/drivers/char/tty_io.c
    @@ -1110,9 +1110,15 @@ static void pty_line_name(struct tty_driver *driver, int index, char *p)
    {
    int i = index + driver->name_base;
    /* ->name is initialized to "ttyp", but "tty" is expected */
    - sprintf(p, "%s%c%x",
    - driver->subtype == PTY_TYPE_SLAVE ? "tty" : driver->name,
    - ptychar[i >> 4 & 0xf], i & 0xf);
    + if (i < 256) {
    + sprintf(p, "%s%c%x",
    + driver->subtype == PTY_TYPE_SLAVE ? "tty" : driver->name,
    + ptychar[i >> 4 & 0xf], i & 0xf);
    + } else { /* Up to 4096 */
    + sprintf(p, "%sf%04x",
    + driver->subtype == PTY_TYPE_SLAVE ? "tty" : driver->name,
    + i - 256);
    + }
    }

    /**




    Cheers,
    Mauro


    \
     
     \ /
      Last update: 2009-09-08 19:53    [W:0.021 / U:62.028 seconds]
    ©2003-2016 Jasper Spaans. hosted at Digital OceanAdvertise on this site