linux-kernel - [PATCH 1/2] dt-bindings: mailbox: add support for referencing controllers solely by node

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Message-Id: <20241219-mbox_request_channel_by_args-v1-1-617a6910f842@linaro.org>
Date: Thu, 19 Dec 2024 13:07:46 +0000
From: Tudor Ambarus <tudor.ambarus@...aro.org>
To: Jassi Brar <jassisinghbrar@...il.com>, Rob Herring <robh@...nel.org>, 
 Krzysztof Kozlowski <krzk+dt@...nel.org>, 
 Conor Dooley <conor+dt@...nel.org>
Cc: linux-kernel@...r.kernel.org, devicetree@...r.kernel.org, 
 linux-samsung-soc@...r.kernel.org, linux-arm-kernel@...ts.infradead.org, 
 andre.draszik@...aro.org, peter.griffin@...aro.org, kernel-team@...roid.com, 
 willmcvicker@...gle.com, daniel.lezcano@...aro.org, 
 vincent.guittot@...aro.org, ulf.hansson@...aro.org, arnd@...db.de, 
 Tudor Ambarus <tudor.ambarus@...aro.org>
Subject: [PATCH 1/2] dt-bindings: mailbox: add support for referencing
 controllers solely by node

There are mailbox clients that can discover the mailbox channel ID at
run-time. For such cases passing the channel identifier via DT is
redundant. Add support for referencing controllers solely by node.

Signed-off-by: Tudor Ambarus <tudor.ambarus@...aro.org>
---
 Documentation/devicetree/bindings/mailbox/mailbox.txt | 19 +++++++++++++++----
 1 file changed, 15 insertions(+), 4 deletions(-)

diff --git a/Documentation/devicetree/bindings/mailbox/mailbox.txt b/Documentation/devicetree/bindings/mailbox/mailbox.txt
index af8ecee2ac68..0c4295a62f61 100644
--- a/Documentation/devicetree/bindings/mailbox/mailbox.txt
+++ b/Documentation/devicetree/bindings/mailbox/mailbox.txt
@@ -5,9 +5,10 @@ assign appropriate mailbox channel to client drivers.
 
 * Mailbox Controller
 
-Required property:
-- #mbox-cells: Must be at least 1. Number of cells in a mailbox
-		specifier.
+Optional property:
+- #mbox-cells: Must be at least 1. Number of cells in a mailbox specifier.
+               The property becomes mandatory for the cases where the clients
+               reference the controller via the mboxes property.
 
 Example:
 	mailbox: mailbox {
@@ -19,7 +20,11 @@ Example:
 * Mailbox Client
 
 Required property:
+Clients must reference the mailbox controller either via the mboxes or mbox
+properties.
 - mboxes: List of phandle and mailbox channel specifiers.
+- mbox: phandle pointing to the controller. Used by clients that can discover
+        the channel identifiers at runtime.
 
 Optional property:
 - mbox-names: List of identifier strings for each mailbox channel.
@@ -29,7 +34,13 @@ Optional property:
 	  communication between the mailbox client and the remote.
 
 
-Example:
+Example using mbox:
+	power-management {
+		...
+		mbox = <&mailbox>;
+	};
+
+Example using mboxes:
 	pwr_cntrl: power {
 		...
 		mbox-names = "pwr-ctrl", "rpc";

-- 
2.47.1.613.gc27f4b7a9f-goog