[spi_device] Auto-generated macros for reserved areas in the buffer

[alphan]

It would be nice to have auto-generated macros for the offset (0xc00) and size (256 bytes) of the SFDP area in spi_device_regs.h and some documentation.

@a-will's comment: I wonder if we ought to have regtool generate constants / macros that associate cmd_info slots with the specific hardware-handled commands.

Update: Also for payload buffer (0xd00) and size.

[alphan]

@eunchan These constants are grouped together here. It would be great if we could have these in spi_device_regs.h for ease of maintenance.

[eunchan]

Let me think about this. Not sure defining the items as parameters in spi_device.hjson is enough or not.

[andreaskurth]

Triaged for spi_device. If I understand correctly, we have the information we need but it would be nice to autogenerate it, so I think we can resolve this post M2.5 --> Type:Icebox Changes deferred to future milestones .