Thread (36 messages) 36 messages, 4 authors, 2026-03-26
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Revisions (3)
  1. v2 current
  2. v3 [diff vs current]
  3. v4 [diff vs current]

[PATCH v2 11/17] fs/stlmfs: Document alternative ioctl based binary interface

From: Cristian Marussi <cristian.marussi@arm.com>
Date: 2026-01-14 11:48:03
Also in: arm-scmi, linux-fsdevel, lkml
Subsystem: documentation, the rest · Maintainers: Jonathan Corbet, Linus Torvalds

Document the additionally provided special files and their usage in the
context of the alternative binary ioctl-based interface.

Signed-off-by: Cristian Marussi <cristian.marussi@arm.com>
---
 Documentation/filesystems/stlmfs.rst | 24 ++++++++++++++++++++++++
 1 file changed, 24 insertions(+)
diff --git a/Documentation/filesystems/stlmfs.rst b/Documentation/filesystems/stlmfs.rst
index 7ea8878098f7..5c23f7e5f12c 100644
--- a/Documentation/filesystems/stlmfs.rst
+++ b/Documentation/filesystems/stlmfs.rst
@@ -112,6 +112,7 @@ the following directory structure::
 	|-- all_des_enable
 	|-- all_des_tstamp_enable
 	|-- available_update_intervals_ms
+	|-- control
 	|-- current_update_interval_ms
 	|-- de_implementation_version
 	|-- des/
@@ -129,6 +130,10 @@ the following directory structure::
 	|-- tlm_enable
 	`-- version
 
+.. Note::
+	The control/ special file can be used to use the alternative
+	binary interface described in include/uapi/linux/scmi.h
+
 Each subdirectory is defined as follows.
 
 des/
@@ -189,6 +194,7 @@ values, as in::
 	scmi_tlm_0/groups/0/
 	|-- available_update_intervals_ms
 	|-- composing_des
+	|-- control
 	|-- current_update_interval_ms
 	|-- des_bulk_read
 	|-- des_single_sample_read
@@ -196,3 +202,21 @@ values, as in::
 	|-- intervals_discrete
 	`-- tstamp_enable
 
+Alternative Binary Interfaces - Special files
+=============================================
+
+Special files are populated across the filesystem so as to implement the support
+of more performant alternative binary interfaces that can be used instead of the
+main human readable ABI.
+
+IOCTLs Interface
+----------------
+
+The ioctl-based interface is detailed in::
+
+	include/uapi/linux/smci.h
+
+The filesystem provides special files named *control/* to be used with the
+ioctl interface mentioned above: note that the behaviour of some of the ioctls
+is dependent on which *control/* file is used to invoke them (as detailed in the
+UAPI header above).
-- 
2.52.0

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