linux-kernel - [PATCH v2] dt-bindings: mfd: Explain lack of child dependency in simple-mfd

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Date: Sun, 23 Jun 2024 15:46:00 +0200
From: Krzysztof Kozlowski <krzysztof.kozlowski@...aro.org>
To: Lee Jones <lee@...nel.org>,
	Rob Herring <robh@...nel.org>,
	Krzysztof Kozlowski <krzk+dt@...nel.org>,
	Conor Dooley <conor+dt@...nel.org>,
	devicetree@...r.kernel.org,
	linux-kernel@...r.kernel.org
Cc: Krzysztof Kozlowski <krzysztof.kozlowski@...aro.org>,
	Linus Walleij <linus.walleij@...aro.org>,
	Arnd Bergmann <arnd@...db.de>,
	Conor Dooley <conor.dooley@...rochip.com>
Subject: [PATCH v2] dt-bindings: mfd: Explain lack of child dependency in simple-mfd

Common mistake of usage of 'simple-mfd' compatible is a dependency of
children on resources acquired and managed by the parent, e.g. clocks.
Extend the simple-mfd documentation to cover this case.

Cc: Linus Walleij <linus.walleij@...aro.org>
Cc: Arnd Bergmann <arnd@...db.de>
Reviewed-by: Conor Dooley <conor.dooley@...rochip.com>
Signed-off-by: Krzysztof Kozlowski <krzysztof.kozlowski@...aro.org>
---

Changes in v2:
1. Rephrase the paragraph, as discussed with Lee.
2. Add Rb tag.
---
 Documentation/devicetree/bindings/mfd/mfd.txt | 15 ++++++++-------
 1 file changed, 8 insertions(+), 7 deletions(-)

diff --git a/Documentation/devicetree/bindings/mfd/mfd.txt b/Documentation/devicetree/bindings/mfd/mfd.txt
index 336c0495c8a3..b938fa26d2ce 100644
--- a/Documentation/devicetree/bindings/mfd/mfd.txt
+++ b/Documentation/devicetree/bindings/mfd/mfd.txt
@@ -17,13 +17,14 @@ A typical MFD can be:
 
 Optional properties:
 
-- compatible : "simple-mfd" - this signifies that the operating system should
-  consider all subnodes of the MFD device as separate devices akin to how
-  "simple-bus" indicates when to see subnodes as children for a simple
-  memory-mapped bus. For more complex devices, when the nexus driver has to
-  probe registers to figure out what child devices exist etc, this should not
-  be used. In the latter case the child devices will be determined by the
-  operating system.
+- compatible : "simple-mfd" - this signifies that the operating system
+  should consider all subnodes of the MFD device as separate and independent
+  devices, so not needing any resources to be provided by the parent device.
+  Similarly to how "simple-bus" indicates when to see subnodes as children for
+  a simple memory-mapped bus.
+  For more complex devices, when the nexus driver has to probe registers to
+  figure out what child devices exist etc, this should not be used. In the
+  latter case the child devices will be determined by the operating system.
 
 - ranges: Describes the address mapping relationship to the parent. Should set
   the child's base address to 0, the physical address within parent's address
-- 
2.43.0