linux-kernel - [PATCH v3 1/7] dt-bindings: input: syna,rmi4: document syna,pdt-fallback-desc

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Message-Id: <20250308-synaptics-rmi4-v3-1-215d3e7289a2@ixit.cz>
Date: Sat, 08 Mar 2025 15:08:37 +0100
From: David Heidelberg via B4 Relay <devnull+david.ixit.cz@...nel.org>
To: Dmitry Torokhov <dmitry.torokhov@...il.com>, 
 Rob Herring <robh@...nel.org>, Krzysztof Kozlowski <krzk+dt@...nel.org>, 
 Conor Dooley <conor+dt@...nel.org>, "Jason A. Donenfeld" <Jason@...c4.com>, 
 Matthias Schiffer <matthias.schiffer@...tq-group.com>, 
 Vincent Huang <vincent.huang@...synaptics.com>
Cc: linux-input@...r.kernel.org, devicetree@...r.kernel.org, 
 linux-kernel@...r.kernel.org, phone-devel@...r.kernel.org, 
 ~postmarketos/upstreaming@...ts.sr.ht, 
 Caleb Connolly <caleb.connolly@...aro.org>, 
 David Heidelberg <david@...t.cz>
Subject: [PATCH v3 1/7] dt-bindings: input: syna,rmi4: document
 syna,pdt-fallback-desc

From: Caleb Connolly <caleb.connolly@...aro.org>

This new property allows devices to specify some register values which
are missing on units with third party replacement displays. These
displays use unofficial touch ICs which only implement a subset of the
RMI4 specification.

Signed-off-by: Caleb Connolly <caleb.connolly@...aro.org>
Signed-off-by: David Heidelberg <david@...t.cz>
---
 Documentation/devicetree/bindings/input/syna,rmi4.yaml | 18 ++++++++++++++++++
 1 file changed, 18 insertions(+)

diff --git a/Documentation/devicetree/bindings/input/syna,rmi4.yaml b/Documentation/devicetree/bindings/input/syna,rmi4.yaml
index b522c8d3ce0db719ff379f2fefbdca79e73d027c..a80ec0c052cb1b7278f0832dd18ebd3256bc0874 100644
--- a/Documentation/devicetree/bindings/input/syna,rmi4.yaml
+++ b/Documentation/devicetree/bindings/input/syna,rmi4.yaml
@@ -49,6 +49,24 @@ properties:
     description:
       Delay to wait after powering on the device.

+  syna,pdt-fallback-desc:
+    $ref: /schemas/types.yaml#/definitions/uint8-matrix
+    description:
+      This property provides fallback values for certain register fields that
+      are missing on devices using third-party replacement displays.
+      These unofficial displays contain touch controllers that claim RMI4
+      compliance but fail to populate the function_number and function_version
+      registers of their Page Descriptor Table (PDT) entries.
+
+      Since the number of required fallback entries depends on the number of
+      Page Descriptor Tables supported by a given device, this property
+      should be provided on a best-effort basis.
+
+    items:
+      items:
+        - description: The 5th byte of the PDT entry (function number)
+        - description: The 4th byte of the PDT entry (version value)
+
   vdd-supply: true
   vio-supply: true

-- 
2.47.2