Messages in this thread | | | Date | Wed, 5 Feb 2014 15:05:07 +0100 | Subject | Re: [systemd-devel] [PATCH] tty: Set correct tty name in 'active' sysfs attribute | From | David Herrmann <> |
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Hi
On Wed, Feb 5, 2014 at 2:53 PM, Peter Hurley <peter@hurleysoftware.com> wrote: > On 02/05/2014 07:53 AM, David Herrmann wrote: >> >> Hi >> >> On Wed, Feb 5, 2014 at 11:11 AM, Hannes Reinecke <hare@suse.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. >>> >>> Cc: Lennart Poettering <lennart@poettering.net> >>> Cc: Kay Sievers <kay@vrfy.org> >>> Signed-off-by: Werner Fink <werner@suse.de> >>> Signed-off-by: Hannes Reinecke <hare@suse.de> >>> --- >>> drivers/tty/tty_io.c | 14 ++++++++++++-- >>> 1 file changed, 12 insertions(+), 2 deletions(-) >>> >>> diff --git a/drivers/tty/tty_io.c b/drivers/tty/tty_io.c >>> index c74a00a..17db8ca 100644 >>> --- a/drivers/tty/tty_io.c >>> +++ b/drivers/tty/tty_io.c >>> @@ -3545,9 +3545,19 @@ static ssize_t show_cons_active(struct device >>> *dev, >>> if (i >= ARRAY_SIZE(cs)) >>> break; >>> } >>> - while (i--) >>> + while (i--) { >>> + const struct tty_driver *driver; >>> + const char *name = cs[i]->name; >>> + int index = cs[i]->index; >>> + >>> + driver = cs[i]->device(cs[i], &index); >>> + if (driver) { >>> + index += driver->name_base; >>> + name = driver->name; >>> + } >>> count += sprintf(buf + count, "%s%d%c", >>> - cs[i]->name, cs[i]->index, i ? ' >>> ':'\n'); >>> + name, index, i ? ' ':'\n'); >>> + } >> >> >> Nice catch and indeed, systemd already relies on these names to be >> identical to their char-dev name. Fortunately, VTs and most serial >> devices register the console with the same name as the TTY, so we're >> fine. > > > What device did this trip over?
I haven't seen one so far, but to me it's a coincident, not something we should rely on.
> Also, this file is not private to systemd. Maybe these changes should > be forked into a different sysfs attribute, "active_devices"?
What's the use-case to return the name of the console-driver? There is no way for user-space to read active console-drivers anywhere so I think returning the TTY makes more sense. We already have working user-space that can spawn gettys on active consoles via this file. I am open to change this to "active_devices" as the existing interface was clearly not designed to return the device-names.
However, given the fact that both matched so far, I think changing the existing interface to the only user I am aware of is better than adding a new interface just to keep this unused attribute. But obviously it's the maintainer's/your decision and you might know user-space which requires the console-names instead of the tty-names. So please let us know which way to go as we would like to see a reliable way to match active consoles to TTY devices for automated getty-startup.
Thanks David
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