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Thu, 09 Apr 2026 10:16:50 -0700 (PDT) Date: Thu, 9 Apr 2026 10:16:46 -0700 From: Dmitry Torokhov To: Conor Dooley Cc: Jingyuan Liang , Jiri Kosina , Benjamin Tissoires , Jonathan Corbet , Mark Brown , Steven Rostedt , Masami Hiramatsu , Mathieu Desnoyers , Rob Herring , Krzysztof Kozlowski , Conor Dooley , linux-input@vger.kernel.org, linux-doc@vger.kernel.org, linux-kernel@vger.kernel.org, linux-spi@vger.kernel.org, linux-trace-kernel@vger.kernel.org, devicetree@vger.kernel.org, hbarnor@chromium.org, tfiga@chromium.org, Dmitry Antipov , Jarrett Schultz Subject: Re: [PATCH v3 09/11] dt-bindings: input: Document hid-over-spi DT schema Message-ID: References: <20260402-send-upstream-v3-0-6091c458d357@chromium.org> <20260402-send-upstream-v3-9-6091c458d357@chromium.org> <20260409-defuse-thank-4b038128fac5@spud> Precedence: bulk X-Mailing-List: linux-doc@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20260409-defuse-thank-4b038128fac5@spud> On Thu, Apr 09, 2026 at 05:02:11PM +0100, Conor Dooley wrote: > On Thu, Apr 02, 2026 at 01:59:46AM +0000, Jingyuan Liang wrote: > > Documentation describes the required and optional properties for > > implementing Device Tree for a Microsoft G6 Touch Digitizer that > > supports HID over SPI Protocol 1.0 specification. > > > > The properties are common to HID over SPI. > > > > Signed-off-by: Dmitry Antipov > > Signed-off-by: Jarrett Schultz > > Signed-off-by: Jingyuan Liang > > --- > > .../devicetree/bindings/input/hid-over-spi.yaml | 126 +++++++++++++++++++++ > > 1 file changed, 126 insertions(+) > > > > diff --git a/Documentation/devicetree/bindings/input/hid-over-spi.yaml b/Documentation/devicetree/bindings/input/hid-over-spi.yaml > > new file mode 100644 > > index 000000000000..d1b0a2e26c32 > > --- /dev/null > > +++ b/Documentation/devicetree/bindings/input/hid-over-spi.yaml > > @@ -0,0 +1,126 @@ > > +# SPDX-License-Identifier: (GPL-2.0-only OR BSD-2-Clause) > > +%YAML 1.2 > > +--- > > +$id: http://devicetree.org/schemas/input/hid-over-spi.yaml# > > +$schema: http://devicetree.org/meta-schemas/core.yaml# > > + > > +title: HID over SPI Devices > > + > > +maintainers: > > + - Benjamin Tissoires > > + - Jiri Kosina > > Why them and not you, the developers of the series? > > > + > > +description: |+ > > + HID over SPI provides support for various Human Interface Devices over the > > + SPI bus. These devices can be for example touchpads, keyboards, touch screens > > + or sensors. > > + > > + The specification has been written by Microsoft and is currently available > > + here: https://www.microsoft.com/en-us/download/details.aspx?id=103325 > > + > > + If this binding is used, the kernel module spi-hid will handle the > > + communication with the device and the generic hid core layer will handle the > > + protocol. > > This is not relevant to the binding, please remove it. > > > + > > +allOf: > > + - $ref: /schemas/input/touchscreen/touchscreen.yaml# > > + > > +properties: > > + compatible: > > + oneOf: > > + - items: > > + - enum: > > + - microsoft,g6-touch-digitizer > > + - const: hid-over-spi > > + - description: Just "hid-over-spi" alone is allowed, but not recommended. > > + const: hid-over-spi > > Why is it allowed but not recommended? Seems to me like we should > require device-specific compatibles. Why would we want to change the driver code to add a new compatible each time a vendor decides to create a chip that is fully hid-spi-protocol compliant? Or is the plan to still allow "hid-over-spi" fallback but require device-specific compatible that will be ignored unless there is device-specific quirk needed? > > > + > > + reg: > > + maxItems: 1 > > + > > + interrupts: > > + maxItems: 1 > > + > > + reset-gpios: > > + maxItems: 1 > > + description: > > + GPIO specifier for the digitizer's reset pin (active low). The line must > > + be flagged with GPIO_ACTIVE_LOW. > > + > > + vdd-supply: > > + description: > > + Regulator for the VDD supply voltage. > > + > > + input-report-header-address: > > + $ref: /schemas/types.yaml#/definitions/uint32 > > + minimum: 0 > > + maximum: 0xffffff > > + description: > > + A value to be included in the Read Approval packet, listing an address of > > + the input report header to be put on the SPI bus. This address has 24 > > + bits. > > + > > + input-report-body-address: > > + $ref: /schemas/types.yaml#/definitions/uint32 > > + minimum: 0 > > + maximum: 0xffffff > > + description: > > + A value to be included in the Read Approval packet, listing an address of > > + the input report body to be put on the SPI bus. This address has 24 bits. > > + > > + output-report-address: > > + $ref: /schemas/types.yaml#/definitions/uint32 > > + minimum: 0 > > + maximum: 0xffffff > > + description: > > + A value to be included in the Output Report sent by the host, listing an > > + address where the output report on the SPI bus is to be written to. This > > + address has 24 bits. > > + > > + read-opcode: > > + $ref: /schemas/types.yaml#/definitions/uint8 > > + description: > > + Value to be used in Read Approval packets. 1 byte. > > + > > + write-opcode: > > + $ref: /schemas/types.yaml#/definitions/uint8 > > + description: > > + Value to be used in Write Approval packets. 1 byte. > > Why can none of these things be determined from the device's compatible? > On the surface, they like the kinds of things that could/should be. Why would we want to keep tables of these values in the kernel and again have to update the driver for each new chip? It also probably firmware-dependent. Thanks. -- Dmitry