[PATCH 3/4] cpumask: add a "none" alias to complement "all"

Paul Gortmaker
2020-11-10T04:07:24Z

With global support for a CPU list alias of "all", it seems to just make
sense to also trivially extend support for an opposite "none" specifier.

Signed-off-by: Paul Gortmaker <paul.gortmaker@windriver.com>
---
Documentation/admin-guide/kernel-parameters.rst | 6 ++++++
lib/cpumask.c | 5 +++++
2 files changed, 11 insertions(+)

diff --git a/Documentation/admin-guide/kernel-parameters.rst b/Documentation/admin-guide/kernel-parameters.rst
index ef98ca700946..9e1c4522e1f0 100644
--- a/Documentation/admin-guide/kernel-parameters.rst
+++ b/Documentation/admin-guide/kernel-parameters.rst
@@ -76,6 +76,12 @@ is equivalent to "foo_cpus=0-N" -- where "N" is the numerically last CPU on
the system, thus avoiding looking up the value in "/sys/devices/system/cpu"
in advance on each deployed system.

+ foo_cpus=none
+
+will provide an empty/cleared cpu mask for the associated boot argument.
+
+Note that "all" and "none" are not necessarily valid/sensible input values
+for each available parameter expecting a CPU list.

This document may not be entirely up to date and comprehensive. The command
"modinfo -p ${modulename}" shows a current list of all parameters of a loadable
diff --git a/lib/cpumask.c b/lib/cpumask.c
index 15599cdf5db6..eb8b1c92501e 100644
--- a/lib/cpumask.c
+++ b/lib/cpumask.c
@@ -110,6 +110,11 @@ int cpulist_parse(const char *buf, struct cpumask *dstp)
return 0;
}

+ if (!strcmp(buf, "none")) {
+ cpumask_clear(dstp);
+ return 0;