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

[Adrian Fiergolski]

On 07.07.2020 12:25, Mark Brown wrote:
> 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.

I see your point here. I could evaluate how complicated it would be to
abstract the spi-daisy_chain driver as an SPI controller for its nodes.

Regards,

Adrian