linux-kernel - Re: [PATCH v5 2/2] iio: humidity: hdc100x: add manufacturer and device ID check

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Message-ID: <CAHp75VcZqTpmvVV=u4t=fdx=ffzksoWVDFZmq6Lfr6DrFrB2aA@mail.gmail.com>
Date:   Mon, 1 Aug 2022 10:22:16 +0200
From:   Andy Shevchenko <andy.shevchenko@...il.com>
To:     Potin Lai <potin.lai.pt@...il.com>
Cc:     Jonathan Cameron <jic23@...nel.org>,
        Lars-Peter Clausen <lars@...afoo.de>,
        Patrick Williams <patrick@...cx.xyz>,
        Potin Lai <potin.lai@...ntatw.com>,
        linux-iio <linux-iio@...r.kernel.org>,
        Linux Kernel Mailing List <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH v5 2/2] iio: humidity: hdc100x: add manufacturer and
 device ID check

On Mon, Aug 1, 2022 at 3:52 AM Potin Lai <potin.lai.pt@...il.com> wrote:
> On 7/31/22 20:09, Jonathan Cameron wrote:

...

> In our hardware board, we have "ti,hdc1080" as main source, and "silabs,si7020"
> for 2nd source. This two chip are locate at same bus and same slave address,
> and we want to use multiple compatibles to support both chips with single device
> node in device tree.
>
> Ex:
> compatible = "ti,hdc1099", "silabs,si7020";

This is simply broken DT, you must not put incompatible hardware on
the same compatible string. DT is by definition the description of a
certain platform. What you showed is a combination of incompatible
chips in a single DT.

> In order to support this, I need to add ID checking mechanism into the current
> hdc100x driver, so the si7020 chip will fail to probe with hdc100x driver
> (because the ID checking is not failed), then success probe with si7020.
>
> Base on you explanation, it looks multiple compatibles is not suitable in this
> case? Would you mind advise us what would be the better approach for our case?

If I may advise... fix your DT by dropping the wrong compatible item.

-- 
With Best Regards,
Andy Shevchenko