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| author | Alan Cox <alan@llwyncelyn.cymru> | 2017-06-02 15:49:30 +0300 |
|---|---|---|
| committer | Greg Kroah-Hartman <gregkh@linuxfoundation.org> | 2017-06-03 12:43:46 +0300 |
| commit | 8a8dabf2dd68caff842d38057097c23bc514ea6e (patch) | |
| tree | 98e019474882e4f4ea47ac77e162c86f3540c726 /include/uapi/linux/tty.h | |
| parent | 47f58e32a27c647de0963386d2714d570b38e3d3 (diff) | |
| download | linux-8a8dabf2dd68caff842d38057097c23bc514ea6e.tar.xz | |
tty: handle the case where we cannot restore a line discipline
Historically the N_TTY driver could never fail but this has become broken over
time. Rather than trying to rewrite half the ldisc layer to fix the breakage
introduce a second level of fallback with an N_NULL ldisc which cannot fail,
and thus restore the guarantees required by the ldisc layer.
We still try and fail to N_TTY first. It's much more useful to find yourself
back in your old ldisc (first attempt) or in N_TTY (second attempt), and while
I'm not aware of any code out there that makes those assumptions it's good to
drive(r) defensively.
Signed-off-by: Alan Cox <alan@linux.intel.com>
Reported-by: Dmitry Vyukov <dvyukov@google.com>
Tested-by: Dmitry Vyukov <dvyukov@google.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Diffstat (limited to 'include/uapi/linux/tty.h')
| -rw-r--r-- | include/uapi/linux/tty.h | 1 |
1 files changed, 1 insertions, 0 deletions
diff --git a/include/uapi/linux/tty.h b/include/uapi/linux/tty.h index e7855dffd592..cf1455396df0 100644 --- a/include/uapi/linux/tty.h +++ b/include/uapi/linux/tty.h @@ -36,5 +36,6 @@ #define N_TRACEROUTER 24 /* Trace data routing for MIPI P1149.7 */ #define N_NCI 25 /* NFC NCI UART */ #define N_SPEAKUP 26 /* Speakup communication with synths */ +#define N_NULL 27 /* Null ldisc used for error handling */ #endif /* _UAPI_LINUX_TTY_H */ |