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

Commit 5aa068ea40 ("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.

Link: http://lkml.kernel.org/r/0102016cf1b26630-8e9b337b-da49-43c6-b028-4250c2fac3ef-000000@eu-west-1.amazonses.com
Cc: Steven Rostedt <rostedt@goodmis.org>
Cc: linux-kernel@vger.kernel.org
Signed-off-by: James Byrne <james.byrne@origamienergy.com>
Reviewed-by: Sergey Senozhatsky <sergey.senozhatsky@gmail.com>
Signed-off-by: Petr Mladek <pmladek@suse.com>
This commit is contained in:
James Byrne 2019-09-02 11:18:16 +00:00 committed by Petr Mladek
parent 35c35493b0
commit 085a3a8fdf
1 changed files with 7 additions and 8 deletions
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15
Documentation/ABI/testing/dev-kmsg
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@ -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 The logged line can be prefixed with a <N> syslog prefix, which
carries the syslog priority and facility. The single decimal carries the syslog priority and facility. The single decimal
prefix number is composed of the 3 lowest bits being the syslog 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 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 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 +sound:card0 - subsystem:devname
The flags field carries '-' by default. A 'c' indicates a The flags field carries '-' by default. A 'c' indicates a
fragment of a line. All following fragments are flagged with fragment of a line. Note, that these hints about continuation
'+'. Note, that these hints about continuation lines are not lines are not necessarily correct, and the stream could be
necessarily correct, and the stream could be interleaved with interleaved with unrelated messages, but merging the lines in
unrelated messages, but merging the lines in the output the output usually produces better human readable results. A
usually produces better human readable results. A similar similar logic is used internally when messages are printed to
logic is used internally when messages are printed to the the console, /proc/kmsg or the syslog() syscall.
console, /proc/kmsg or the syslog() syscall.
By default, kernel tries to avoid fragments by concatenating By default, kernel tries to avoid fragments by concatenating
when it can and fragments are rare; however, when extended when it can and fragments are rare; however, when extended