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

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Message-ID: <20260114114638.2290765-12-cristian.marussi@arm.com>
Date: Wed, 14 Jan 2026 11:46:15 +0000
From: Cristian Marussi <cristian.marussi@....com>
To: linux-kernel@...r.kernel.org,
	linux-arm-kernel@...ts.infradead.org,
	arm-scmi@...r.kernel.org,
	linux-fsdevel@...r.kernel.org
Cc: sudeep.holla@....com,
	james.quinlan@...adcom.com,
	f.fainelli@...il.com,
	vincent.guittot@...aro.org,
	etienne.carriere@...com,
	peng.fan@....nxp.com,
	michal.simek@....com,
	dan.carpenter@...aro.org,
	d-gole@...com,
	jonathan.cameron@...wei.com,
	elif.topuz@....com,
	lukasz.luba@....com,
	philip.radford@....com,
	souvik.chakravarty@....com,
	Cristian Marussi <cristian.marussi@....com>
Subject: [PATCH v2 11/17] fs/stlmfs: Document alternative ioctl based binary interface

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@....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