Re: [PATCH v2 1/2] spi: Add the SPI daisy chain support.

[Mark Brown]

On Mon, Jul 06, 2020 at 09:57:53PM +0200, Geert Uytterhoeven wrote:
> On Mon, Jul 6, 2020 at 6:18 PM Mark Brown <broonie@xxxxxxxxxx> wrote:

> > It would really help to have an example of how a client device will use
> > this, right now it's a bit hard to follow.  Overall it feels like this
> > should be better abstracted, right now there's lots of ifdefs throughout
> > the code which make things unclear and also seem like they're going to
> > be fragile long term since realistically very few systems will be using
> > this.

> Can't the ifdefs be avoided by implementing this as a new SPI controller?
> I.e. the daisy chain driver will operate as a slave of the parent SPI
> controller,
> but will expose a new SPI bus to the daisy-chained slaves.

Yes, that might work.  I do worry about locking issues with having a SPI
controller connected via SPI but we mostly only lock at the controller
level so it's probably fine.  Not sure how this would perform either.

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