[PATCH v4 30/31] fs/stlmfs: Document lazy mode and related mount option

[Cristian Marussi]

Document optional lazy enumeration behaviour and related mount option.

Cc: Jonathan Corbet <corbet at lwn.net>
Cc: Shuah Khan <skhan at linuxfoundation.org>
Cc: linux-doc at vger.kernel.org
Signed-off-by: Cristian Marussi <cristian.marussi at arm.com>
---
 Documentation/filesystems/stlmfs.rst | 21 +++++++++++++++++++--
 1 file changed, 19 insertions(+), 2 deletions(-)

diff --git a/Documentation/filesystems/stlmfs.rst b/Documentation/filesystems/stlmfs.rst
index b5b3cd649775..fe69d40f9249 100644
--- a/Documentation/filesystems/stlmfs.rst
+++ b/Documentation/filesystems/stlmfs.rst
@@ -74,8 +74,12 @@ Design
 STLMFS is a pseudo filesystem used to expose ARM SCMI Telemetry data
 discovered dynamically at run-time via SCMI.
 
-Inodes are all dynamically created at mount-time from a dedicated
-kmem_cache based on the gathered available SCMI Telemetry information.
+Normally all of the top level file/inodes are dynamically created at
+mount-time from a dedicated kmem_cache based on the gathered available
+SCMI Telemetry information, but it is possible to enable a lazy enumeration
+and FS population mode that delays SCMI Telemetry resources enumerations
+and related FS population till the moment a user steps into the related FS
+subdirectories: *des/* *groups/* and *components/*.
 
 Since inodes represent the discovered Telemetry entities, which in turn are
 statically defined at the platform level and immutable throughout the same
@@ -128,6 +132,19 @@ Note that all of the above options are explicitly designed NOT to support
 a remount operation, so as not have surprising effects on permissions of
 already discovered/created telemetry files.
 
+It is possible to mount it in lazy-mode by using the *lazy* mount option::
+
+	mount -t stlmfs -o lazy none /sys/fs/arm_telemetry
+
+In this latter case, the des/ groups/ and components/ directory will be
+created empty at mount-time and only filled later when 'walked in'.
+
+This allows a user to benefit from a lazy enumeration scheme of the SCMI
+Telemetry resources by delaying such, usually expensive, message exchanges
+to the last possible moment: ideally, even never, if using some of the
+other alternative binary interfaces that does not need any resource
+enumeration at all.
+
 Usage
 =====
 
-- 
2.54.0