linux-kernel - Re: [PATCH v2 0/2] iio: humidity: si7020: Check device property for skipping reset in probe

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Date:   Thu, 12 May 2022 17:48:59 +0100
From:   Jonathan Cameron <Jonathan.Cameron@...wei.com>
To:     Eddie James <eajames@...ux.ibm.com>
CC:     <linux-iio@...r.kernel.org>, <devicetree@...r.kernel.org>,
        <linux-kernel@...r.kernel.org>,
        <krzysztof.kozlowski+dt@...aro.org>, <robh+dt@...nel.org>,
        <lars@...afoo.de>, <jic23@...nel.org>, <miltonm@...ibm.com>
Subject: Re: [PATCH v2 0/2] iio: humidity: si7020: Check device property for
 skipping reset in probe

On Thu, 12 May 2022 11:20:18 -0500
Eddie James <eajames@...ux.ibm.com> wrote:

> I2C commands issued after the SI7020 is starting up or after reset
> can potentially upset the startup sequence. Therefore, the host
> needs to wait for the startup sequence to finish before issuing
> further i2c commands. This is impractical in cases where the SI7020
> is on a shared bus or behind a mux, which may switch channels at
> any time (generating I2C traffic). Therefore, check for a device
> property that indicates that the driver should skip resetting the
> device when probing.

Why not lock the bus?  It's not ideal, but then not resetting and hence
potentially ending up in an unknown state isn't great either.

Jonathan

> 
> Changes since v1:
>  - Fix dt binding document
> 
> Eddie James (2):
>   dt-bindings: iio: humidity: Add si7020 bindings
>   iio: humidity: si7020: Check device property for skipping reset in probe
> 
>  .../bindings/iio/humidity/silabs,si7020.yaml  | 47 +++++++++++++++++++
>  .../devicetree/bindings/trivial-devices.yaml  |  2 -
>  drivers/iio/humidity/si7020.c                 | 14 +++---
>  3 files changed, 55 insertions(+), 8 deletions(-)
>  create mode 100644 Documentation/devicetree/bindings/iio/humidity/silabs,si7020.yaml
>