RE: [PATCH v26 2/4] dt-bindings: i2c: ast2600-i2c.yaml: Add global-regs and transfer-mode properties

> Subject: Re: [PATCH v26 2/4] dt-bindings: i2c: ast2600-i2c.yaml: Add global-regs
> and transfer-mode properties
> 
> Hi Ryan,
> 
> > > Not at all - the next paragraph was my attempt at a recap of those,
> > > but Ryan, please correct me if I am wrong on any of those points.
> >
> > Your understanding is correct; the byte and buffer mode is mostly the same.
> > And also mode should be decided before xfer, due to the
> > controller/target both use the same xfer mode, not decide by transfer time.
> > The original my submit is only buffer mode and dma mode, and use only
> > one Boolean property, aspeed,i2c-dma-enabled, but someone suggest add
> > byte mode select, so I start to add at v17. I can drop the byte mode, if this is
> confused.
> >
> > byte mode request:
> > https://lore.kernel.org/all/010e55e9-d58b-444c-ab57-ddf8c75f2390@gmail
> > .com/
> 
> I understand that there may be valid uses for byte mode, but that does not
> mean the configuration belongs in the device tree.
> 
> We do not seem to have much data on what those valid uses are, but I am
> assuming it is not an attribute of the controller peripheral hardware.

OK will remove it in yaml file, instead Boolean property, aspeed,i2c-dma-enabled
> 
> [As an example: I suspect MCTP cannot be fully spec-compliant without byte
> mode, in order to support the NAK window on target-mode RX. In that case we
> can enforce byte mode when the controller is selected for MCTP use, without
> requiring a mode selection property in the DT]
> 
> > > Ryan: I think this gives us a much cleaner approach to the binding.
> > Thanks the feedback, do you mean, just one boolean property for mode
> > selection, Am I right?
> 
> The property would not select a mode, it just indicates whether DMA is
> available.
> 
> A driver implementation can use that indication, along with any other
> configuration data, in order to select a mode. The Linux driver implementation
> may use other runtime facilities to control that selection, if you need, like sysfs
> or configfs.

Do you mean sysfs select support mode selection(byte, buffer, dma)
Or just force byte mode? 

> 
> Cheers,
> 
> 
> Jeremy