linux-kernel - Re: [RFC,v2 2/6] i2c: add I2C Address Translator (ATR) support

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Date:   Tue, 10 Sep 2019 18:16:30 +0100
From:   Wolfram Sang <wsa@...-dreams.de>
To:     Luca Ceresoli <luca@...aceresoli.net>
Cc:     Vladimir Zapolskiy <vz@...ia.com>,
        jacopo mondi <jacopo@...ndi.org>,
        Peter Rosin <peda@...ntia.se>, linux-media@...r.kernel.org,
        linux-i2c@...r.kernel.org, devicetree@...r.kernel.org,
        linux-kernel@...r.kernel.org,
        Mauro Carvalho Chehab <mchehab@...nel.org>,
        Rob Herring <robh+dt@...nel.org>,
        Mark Rutland <mark.rutland@....com>,
        Sakari Ailus <sakari.ailus@...ux.intel.com>,
        Hans Verkuil <hverkuil-cisco@...all.nl>,
        Laurent Pinchart <laurent.pinchart@...asonboard.com>,
        Kieran Bingham <kieran.bingham@...asonboard.com>
Subject: Re: [RFC,v2 2/6] i2c: add I2C Address Translator (ATR) support


> Here i2c-0 is the "local" bus, i2c-4 and i2c-5 are the remote busses on
> ports 0 and 1. As you can see the eeproms are accessed using a name like
> "4-0050", meaning physical slave address 0x50 on bus 4. No alias is needed.
> 
> Should you want to know the alias, perhaps for debugging (it's the
> address you'll see on your logic analyzer), they are shown in the kernel
> log.

And to add to that: The aliases on i2c-0 will be marked busy and show up
as used if you run i2cdetect. So, you'd need a force-flag if you'd want
to access them from userspace.


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