[PATCH 08/12] doc: binding: pwrseq-usb-generic: add binding doc for generic usb power sequence driver

Mark Brown broonie at kernel.org
Mon Jun 20 10:06:10 PDT 2016

On Mon, Jun 20, 2016 at 11:16:07AM -0500, Rob Herring wrote:
> On Mon, Jun 20, 2016 at 07:26:51PM +0800, Peter Chen wrote:

> > If the node has property "power-sequence", the pwrseq core will create
> > related platform device, and the driver under pwrseq driver will handle
> > power sequence stuffs. 

> This I have issue with. If you are creating a platform device here, you 
> are trying to work-around limitations in the linux driver model. Either 
> we need some sort of pre-probe hook to the drivers to call or each 
> parent node driver is responsible for checking and calling pwr-seq 
> functions for child nodes. e.g. The host controller calls pwr-seq for 
> the hub, the hub driver calls the power seq for the asix chip. Soon as 
> we have a case too complex for the generic pwr-seq, we're going to need 
> the pre-probe hook as I don't want to see a continual expansion of 
> generic pwr-seq binding for ever more complex cases.

I think it's fairly clear that we need one or both of these mechanisms
for enumerable buses in embedded contexts - it's something that keeps
croping up.
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