From c2faf737abfb10f88f2d2612d573e9edc3c42c37 Mon Sep 17 00:00:00 2001 From: Max Staudt Date: Fri, 11 Feb 2022 15:10:36 +0100 Subject: [PATCH] tty: Reserve ldisc 29 for development purposes It's handy to have an ldisc number free for out-of-tree testing. This way, a new ldisc can be developed on any running system, without having to recompile the kernel just to define a new number. This is the highest number (and also the last one) available under the old numbering scheme, so let's reserve it before it's too late. From now on, every new ldisc upstreamed will have to increment NR_LDISCS in lockstep with its addition to the table in tty.h. Signed-off-by: Max Staudt Link: https://lore.kernel.org/r/20220211141036.6403-1-max@enpas.org Signed-off-by: Greg Kroah-Hartman --- include/uapi/linux/tty.h | 6 ++++-- 1 file changed, 4 insertions(+), 2 deletions(-) diff --git a/include/uapi/linux/tty.h b/include/uapi/linux/tty.h index a58deb3061eb..9d0f06bfbac3 100644 --- a/include/uapi/linux/tty.h +++ b/include/uapi/linux/tty.h @@ -6,8 +6,6 @@ * 'tty.h' defines some structures used by tty_io.c and some defines. */ -#define NR_LDISCS 30 - /* line disciplines */ #define N_TTY 0 #define N_SLIP 1 @@ -39,5 +37,9 @@ #define N_SPEAKUP 26 /* Speakup communication with synths */ #define N_NULL 27 /* Null ldisc used for error handling */ #define N_MCTP 28 /* MCTP-over-serial */ +#define N_DEVELOPMENT 29 /* Manual out-of-tree testing */ + +/* Always the newest line discipline + 1 */ +#define NR_LDISCS 30 #endif /* _UAPI_LINUX_TTY_H */