linux-kernel - Re: [PATCH v5 0/6] Add spi-hid, transport for HID over SPI bus

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Message-ID: <86b63b7b-afda-d7f4-7bfa-175085d5a8ef@gmail.com>
Date:   Tue, 9 Aug 2022 02:53:26 +0200
From:   Maximilian Luz <luzmaximilian@...il.com>
To:     jaschultzms@...il.com
Cc:     benjamin.tissoires@...hat.com, biju.das.jz@...renesas.com,
        bjorn.andersson@...aro.org, catalin.marinas@....com,
        corbet@....net, devicetree@...r.kernel.org, dmanti@...rosoft.com,
        dmitry.baryshkov@...aro.org, dmitry.torokhov@...il.com,
        geert+renesas@...der.be, jaschultz@...rosoft.com, jikos@...nel.org,
        krzysztof.kozlowski+dt@...aro.org,
        linux-arm-kernel@...ts.infradead.org, linux-doc@...r.kernel.org,
        linux-input@...r.kernel.org, linux-kernel@...r.kernel.org,
        marcel.ziswiler@...adex.com, robh+dt@...nel.org,
        shawnguo@...nel.org, vkoul@...nel.org, will@...nel.org
Subject: Re: [PATCH v5 0/6] Add spi-hid, transport for HID over SPI bus

On 8/7/22 09:58, Jarrett Schultz <jaschultzms@...il.com> wrote:
> Surface Duo devices use a touch digitizer that communicates to the main
> SoC via SPI and presents itself as a HID device. This patch's goal is to
> add the spi-hid transport driver to drivers/hid. The driver follows the
> publically available HID Over SPI Protocol Specification version 1.0.

As far as I can tell based on the downstream code you provide in [1],
your proposed driver (and v1.0 spec) is incompatible with the version
used on current Surface devices (Surface Duo 1 and 2, Surface Pro X, and
I assume some AMD/x86 based devices on which you also use spi-hid for the
digitizer). On those, SPI_HID_SUPPORTED_VERSION is 0x0100 whereas it is
0x0300 for the driver proposed here, along with at least some protocol
struct changes.

Do you have any plans on supporting those devices (i.e. protocol version
0x0100) at some point?

Regards,
Max

[1]: https://github.com/microsoft/surface-duo-oss-kernel.msm-5..4/tree/surfaceduo2/11/2022.108.8/drivers/hid/spi-hid