linux-kernel - Re: [RFC PATCH v2 2/6] i2c: allow DT nodes without 'compatible'

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Date:   Wed, 15 Apr 2020 09:07:56 +0100
From:   Kieran Bingham <kieran.bingham+renesas@...asonboard.com>
To:     Wolfram Sang <wsa@...-dreams.de>,
        Luca Ceresoli <luca@...aceresoli.net>
Cc:     Wolfram Sang <wsa+renesas@...g-engineering.com>,
        linux-i2c@...r.kernel.org, linux-renesas-soc@...r.kernel.org,
        linux-i3c@...ts.infradead.org,
        Niklas Söderlund <niklas.soderlund@...natech.se>,
        Jacopo Mondi <jacopo@...ndi.org>,
        Laurent Pinchart <laurent.pinchart@...asonboard.com>,
        Vladimir Zapolskiy <vz@...ia.com>,
        linux-kernel@...r.kernel.org,
        Geert Uytterhoeven <geert+renesas@...der.be>,
        Rob Herring <robh@...nel.org>
Subject: Re: [RFC PATCH v2 2/6] i2c: allow DT nodes without 'compatible'

Hi Wolfram,

On 15/04/2020 08:59, Wolfram Sang wrote:
> 
>> As I said in the reply to v1, I think we should reserve addresses also
>> when there is a compatible string but no matching driver, but this is
>> another story and can be handled separately.
> 
> Unless I misunderstand you, I think they do already. Note that
> only 'i2cdetect' shows a device as busy *IFF* there is a driver bound to
> it. The internal 'i2c_check_addr_busy' does not care about a driver
> being bound. You can check this by trying to use
> i2c_new_ancillary_device() with an address which is already described in
> DT but which driver is disabled.

Aha, is it easy enough to distinguish that difference in user-space so
that we can present a specific character to indicate this in i2cdetect?
Or is that not so easy?

--
Kieran