[PATCH] regcache: Improve documentation of available cache types

[Mark Brown <broonie@kernel.org>]

There is some user confusion about which cache types to choose when which
is not helped by the lack of any central documentation providing an
overview of what's available. Provide a short overview in the API header to
try to help reduce this.

Signed-off-by: Mark Brown <broonie@kernel.org>
---
 include/linux/regmap.h | 9 ++++++++-
 1 file changed, 8 insertions(+), 1 deletion(-)

diff --git a/include/linux/regmap.h b/include/linux/regmap.h
index 122e38161acb..5b59423e786a 100644
--- a/include/linux/regmap.h
+++ b/include/linux/regmap.h
@@ -54,7 +54,14 @@ struct sdw_slave;
 #define REGMAP_UPSHIFT(s)	(-(s))
 #define REGMAP_DOWNSHIFT(s)	(s)
 
-/* An enum of all the supported cache types */
+/*
+ * The supported cache types, the default is no cache.  Any new caches
+ * should usually use the maple tree cache unless they specifically
+ * require that there are never any allocations at runtime and can't
+ * provide defaults in which case they should use the flat cache.  The
+ * rbtree cache *may* have some performance advantage for very low end
+ * systems that make heavy use of cache syncs but is mainly legacy.
+ */
 enum regcache_type {
 	REGCACHE_NONE,
 	REGCACHE_RBTREE,

---
base-commit: 98f7e32f20d28ec452afb208f9cffc08448a2652
change-id: 20240923-regcache-document-types-5ab0e3448b8b

Best regards,
-- 
Mark Brown <broonie@kernel.org>