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| -rw-r--r-- | Documentation/sysctl/ctl_unnumbered.txt | 22 |
1 files changed, 22 insertions, 0 deletions
diff --git a/Documentation/sysctl/ctl_unnumbered.txt b/Documentation/sysctl/ctl_unnumbered.txt new file mode 100644 index 00000000000..23003a8ea3e --- /dev/null +++ b/Documentation/sysctl/ctl_unnumbered.txt @@ -0,0 +1,22 @@ + +Except for a few extremely rare exceptions user space applications do not use +the binary sysctl interface. Instead everyone uses /proc/sys/... with +readable ascii names. + +Recently the kernel has started supporting setting the binary sysctl value to +CTL_UNNUMBERED so we no longer need to assign a binary sysctl path to allow +sysctls to show up in /proc/sys. + +Assigning binary sysctl numbers is an endless source of conflicts in sysctl.h, +breaking of the user space ABI (because of those conflicts), and maintenance +problems. A complete pass through all of the sysctl users revealed multiple +instances where the sysctl binary interface was broken and had gone undetected +for years. + +So please do not add new binary sysctl numbers. They are unneeded and +problematic. + +If you really need a new binary sysctl number please first merge your sysctl +into the kernel and then as a separate patch allocate a binary sysctl number. + +(ebiederm@xmission.com, June 2007) |