[RFC] MFD's relationship with Device Tree (OF)

Michael Walle michael at walle.cc
Mon Jun 22 17:03:59 EDT 2020

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 at 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 at 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?


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