[PATCH] ABI: Update dev-kmsg documentation to match current kernel behaviour

[PATCH] ABI: Update dev-kmsg documentation to match current kernel behaviour

[James Byrne]

Commit 5aa068ea4082 ("printk: remove games with previous record flags")
abolished the practice of setting the log flag to 'c' for the first
continuation line and '+' for subsequent lines. Now all continuation
lines are flagged with 'c' and '+' is never used.

Update the 'dev-kmsg' documentation to remove the reference to the
obsolete '+' flag. In addition, state explicitly that only 8 bits of the
<N> syslog prefix are used for the facility number when writing to
/dev/kmsg.

Signed-off-by: James Byrne <james.byrne@origamienergy.com>
---
 Documentation/ABI/testing/dev-kmsg | 15 +++++++--------
 1 file changed, 7 insertions(+), 8 deletions(-)

diff --git a/Documentation/ABI/testing/dev-kmsg b/Documentation/ABI/testing/dev-kmsg
index fff817efa508..f307506eb54c 100644
--- a/Documentation/ABI/testing/dev-kmsg
+++ b/Documentation/ABI/testing/dev-kmsg
@@ -12,7 +12,7 @@ Description:	The /dev/kmsg character device node provides userspace access
 		The logged line can be prefixed with a <N> syslog prefix, which
 		carries the syslog priority and facility. The single decimal
 		prefix number is composed of the 3 lowest bits being the syslog
-		priority and the higher bits the syslog facility number.
+		priority and the next 8 bits the syslog facility number.
 
 		If no prefix is given, the priority number is the default kernel
 		log priority and the facility number is set to LOG_USER (1). It
@@ -90,13 +90,12 @@ Description:	The /dev/kmsg character device node provides userspace access
 		  +sound:card0 - subsystem:devname
 
 		The flags field carries '-' by default. A 'c' indicates a
-		fragment of a line. All following fragments are flagged with
-		'+'. Note, that these hints about continuation lines are not
-		necessarily correct, and the stream could be interleaved with
-		unrelated messages, but merging the lines in the output
-		usually produces better human readable results. A similar
-		logic is used internally when messages are printed to the
-		console, /proc/kmsg or the syslog() syscall.
+		fragment of a line. Note, that these hints about continuation
+		lines are not necessarily correct, and the stream could be
+		interleaved with unrelated messages, but merging the lines in
+		the output usually produces better human readable results. A
+		similar logic is used internally when messages are printed to
+		the console, /proc/kmsg or the syslog() syscall.
 
 		By default, kernel tries to avoid fragments by concatenating
 		when it can and fragments are rare; however, when extended
-- 
2.17.1

Re: [PATCH] ABI: Update dev-kmsg documentation to match current kernel behaviour

[Sergey Senozhatsky]

On (09/02/19 11:18), James Byrne wrote:
> Commit 5aa068ea4082 ("printk: remove games with previous record flags")
> abolished the practice of setting the log flag to 'c' for the first
> continuation line and '+' for subsequent lines. Now all continuation
> lines are flagged with 'c' and '+' is never used.
>
> Update the 'dev-kmsg' documentation to remove the reference to the
> obsolete '+' flag. In addition, state explicitly that only 8 bits of the
> <N> syslog prefix are used for the facility number when writing to
> /dev/kmsg.
>
> Signed-off-by: James Byrne <james.byrne@origamienergy.com>

Looks good to me.

Reviewed-by: Sergey Senozhatsky <sergey.senozhatsky@gmail.com>

	-ss

Re: [PATCH] ABI: Update dev-kmsg documentation to match current kernel behaviour

[Petr Mladek]

On Tue 2019-09-03 14:02:20, Sergey Senozhatsky wrote:
> On (09/02/19 11:18), James Byrne wrote:
> > Commit 5aa068ea4082 ("printk: remove games with previous record flags")
> > abolished the practice of setting the log flag to 'c' for the first
> > continuation line and '+' for subsequent lines. Now all continuation
> > lines are flagged with 'c' and '+' is never used.
> >
> > Update the 'dev-kmsg' documentation to remove the reference to the
> > obsolete '+' flag. In addition, state explicitly that only 8 bits of the
> > <N> syslog prefix are used for the facility number when writing to
> > /dev/kmsg.
> >
> > Signed-off-by: James Byrne <james.byrne@origamienergy.com>
> 
> Looks good to me.
> 
> Reviewed-by: Sergey Senozhatsky <sergey.senozhatsky@gmail.com>

The patch has been committed into printk.git, branch for-5.4.

Best Regards,
Petr Mladek