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Subject: Re: [RFC] MFD's relationship with Device Tree (OF)
To:     Michael Walle <michael@walle.cc>, Rob Herring <robh+dt@kernel.org>
Cc:     Lee Jones <lee.jones@linaro.org>,
        Andy Shevchenko <andy.shevchenko@gmail.com>,
        Mark Brown <broonie@kernel.org>,
        devicetree <devicetree@vger.kernel.org>,
        Linux Kernel Mailing List <linux-kernel@vger.kernel.org>,
        linux-arm Mailing List <linux-arm-kernel@lists.infradead.org>,
        Linus Walleij <linus.walleij@linaro.org>,
        Guenter Roeck <linux@roeck-us.net>,
        Andy Shevchenko <andriy.shevchenko@linux.intel.com>,
        Robin Murphy <robin.murphy@arm.com>,
        GregKroah-Hartman <gregkh@linuxfoundation.org>,
        Frank Rowand <frowand.list@gmail.com>
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From:   Frank Rowand <frowand.list@gmail.com>
Message-ID: <0e9e25cc-b3f2-926a-31dd-c6fafa7d581b@gmail.com>
Date:   Wed, 24 Jun 2020 16:01:42 -0500
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+Frank (me)

On 2020-06-22 16:03, Michael Walle wrote:
> Am 2020-06-14 12:26, schrieb Michael Walle:
>> Hi Rob,
>>
>> Am 2020-06-10 00:03, schrieb Rob Herring:
>> [..]
>>> Yes, we should use 'reg' whenever possible. If we don't have 'reg',
>>> then you shouldn't have a unit-address either and you can simply match
>>> on the node name (standard DT driver matching is with compatible,
>>> device_type, and node name (w/o unit-address)). We've generally been
>>> doing 'classname-N' when there's no 'reg' to do 'classname@N'.
>>> Matching on 'classname-N' would work with node name matching as only
>>> unit-addresses are stripped.
>>
>> This still keeps me thinking. Shouldn't we allow the (MFD!) device
>> driver creator to choose between "classname@N" and "classname-N".
>> In most cases N might not be made up, but it is arbitrarily chosen;
>> for example you've chosen the bank for the ab8500 reg. It is not
>> a defined entity, like an I2C address if your parent is an I2C bus,
>> or a SPI chip select, or the memory address in case of MMIO. Instead
>> the device driver creator just chooses some "random" property from
>> the datasheet; another device creator might have chosen another
>> property. Wouldn't it make more sense, to just say this MFD provides
>> N pwm devices and the subnodes are matching based on pwm-{0,1..N-1}?
>> That would also be the logical consequence of the current MFD sub
>> device to OF node matching code, which just supports N=1.
>>
> 
> Rob? Lee?
> 
> -michael