linux-kernel - [PATCH v3 0/7] Subject: [PATCH v3 0/7] Input: synaptics-rmi4: add quirks for third party touchscreen controllers

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Message-Id: <20250308-synaptics-rmi4-v3-0-215d3e7289a2@ixit.cz>
Date: Sat, 08 Mar 2025 15:08:36 +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>, methanal <baclofen@...a.io>
Subject: [PATCH v3 0/7] Subject: [PATCH v3 0/7] Input: synaptics-rmi4: add
 quirks for third party touchscreen controllers

With the growing popularity of running upstream Linux on mobile devices,
we're beginning to run into more and more edgecases. The OnePlus 6 is a
fairly well supported 2018 era smartphone, selling over a million units
in it's first 22 days. With this level of popularity, it's almost
inevitable that we get third party replacement displays, and as a
result, replacement touchscreen controllers.

The OnePlus 6 shipped with an extremely usecase specific touchscreen
driver, it implemented only the bare minimum parts of the highly generic
rmi4 protocol, instead hardcoding most of the register addresses.

As a result, the third party touchscreen controllers that are often
found in replacement screens, implement only the registers that the 
downstream driver reads from. They additionally have other restrictions
such as heavy penalties on unaligned reads.

This series attempts to implement the necessary workaround to support  
some of these chips with the rmi4 driver. Although it's worth noting
that at the time of writing there are other unofficial controllers in
the wild that don't work even with these patches.

We have been shipping these patches in postmarketOS for the last several
months, and they are known to not cause any regressions on the OnePlus
6/6T (with the official Synaptics controller), however I don't own any
other rmi4 hardware to further validate this.

---
Changes since v2:
- reworded dt-bindings property description
- fixed the rmi_driver_of_probe definition for non device-tree builds.
- fixed some indentation issues reported by checkpatch
- change rmi_pdt_entry_is_valid() variable to unsigned 
- Link to v2: https://patchwork.kernel.org/project/linux-input/cover/20230929-caleb-rmi4-quirks-v2-0-b227ac498d88@linaro.org/

Changes since v1:
- Improve dt-bindings patch (thanks Rob)
- Add missing cast in patch 5 to fix the pointer arithmetic
- Link to v1: https://lore.kernel.org/r/20230929-caleb-rmi4-quirks-v1-0-cc3c703f022d@linaro.org

---
Caleb Connolly (2):
      dt-bindings: input: syna,rmi4: document syna,pdt-fallback-desc
      Input: synaptics-rmi4 - handle duplicate/unknown PDT entries

methanal (5):
      Input: synaptics-rmi4 - f12: use hardcoded values for aftermarket touch ICs
      Input: synaptics-rmi4 - f55: handle zero electrode count
      Input: synaptics-rmi4 - don't do unaligned reads in IRQ context
      Input: synaptics-rmi4 - read product ID on aftermarket touch ICs
      Input: synaptics-rmi4 - support fallback values for PDT descriptor bytes

 .../devicetree/bindings/input/syna,rmi4.yaml       |  18 +++
 drivers/input/rmi4/rmi_driver.c                    | 140 +++++++++++++++++----
 drivers/input/rmi4/rmi_driver.h                    |   8 ++
 drivers/input/rmi4/rmi_f01.c                       |  14 +++
 drivers/input/rmi4/rmi_f12.c                       | 117 +++++++++++++----
 drivers/input/rmi4/rmi_f55.c                       |   5 +
 include/linux/rmi.h                                |   3 +
 7 files changed, 258 insertions(+), 47 deletions(-)
---
base-commit: 0a2f889128969dab41861b6e40111aa03dc57014
change-id: 20250308-synaptics-rmi4-c832b2f73ceb

Best regards,
-- 
David Heidelberg <david@...t.cz>