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From:   Rob Herring <robh+dt@kernel.org>
Date:   Mon, 1 Jun 2020 11:08:37 -0600
Message-ID: <CAL_JsqJeod3Rm4K_7c3AcH8A4aMKKmT97CcbGpRbG4b0yWzrXA@mail.gmail.com>
Subject: Re: [PATCH v2] check: Add 10bit/slave i2c reg flags support
To:     Wolfram Sang <wsa@the-dreams.de>
Cc:     Serge Semin <Sergey.Semin@baikalelectronics.ru>,
        Devicetree Compiler <devicetree-compiler@vger.kernel.org>,
        Serge Semin <fancer.lancer@gmail.com>,
        Alexey Malahov <Alexey.Malahov@baikalelectronics.ru>,
        Thomas Bogendoerfer <tsbogend@alpha.franken.de>,
        Jarkko Nikula <jarkko.nikula@linux.intel.com>,
        Andy Shevchenko <andriy.shevchenko@linux.intel.com>,
        Frank Rowand <frowand.list@gmail.com>,
        devicetree@vger.kernel.org, Linux I2C <linux-i2c@vger.kernel.org>,
        "linux-kernel@vger.kernel.org" <linux-kernel@vger.kernel.org>
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On Sat, May 30, 2020 at 3:32 AM Wolfram Sang <wsa@the-dreams.de> wrote:
>
>
> > +     addr = reg & 0x3FFFFFFFU;
> > +     snprintf(unit_addr, sizeof(unit_addr), "%x", addr);
>
> Hmm, this hardcoded value will not work if we ever need to add another
> bit. I hope this will never happen, though.

I had this concern and requested the first time this was submitted
(and abandoned) to just mask out the top byte. However, Joel's version
of this fix[1] does some actual checks on 10-bit addressing, so I've
dropped that request.

> > +             if ((reg & (1U << 31)) && addr > 0x3ff)
>
> Same here with bit 31. I haven't checked DTC but can't we import the
> header with the defines into the project? Or is this then a circular
> dependency?

Easier to just duplicate the define here which Joel's patches do.

Rob

[1] https://www.spinics.net/lists/devicetree-compiler/msg03196.html