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