Re: Raspberry Pi zero 2 dtb and devices

[Dave Tyson <dtyson%anduin.org.uk@localhost>]

> Also...  you more or less should use the *SAME* dtb and firmware for the
> same NetBSD kernel.  That is, if you run 9.x, then you should use the
> 9.x dtb and firmware.  To be honest, this isn't quite as strict, but I
> have had to update that from time to time as I have moved forward with
> versions of NetBSD.
> 
> Back to the SPI problem, there is probably something wrong with the spi
> attachment on the RPI with respect to pin assignment.  The dtb, when
> turned back into text, that NetBSD uses seems to imply that the
> functions of the pins are to be alt0, but I can't prove that the SPI
> attachment routine does that, nor am I entirely clear that it should (it
> probably needs to).  I2C works fine out of the box, and doesn't appear
> to set the pins, but I suspect that gets more testing and it may work
> differently anyway.  At one point I found a documentation page out there
> (mostly for Linux) that explained what the lines in the dtb meant,
> including the raw values (0x04 meant use alt0 or some such thing, for
> example).
> 

OK, thanks for that. I'll do a bit of code reading and try and work out what 
is happening,

Thanks also to Michael van Elst regarding the comment about the GPIO interface 
only working on rpi's - I hadn't realised it didn't work on other SOC's. Also 
it is useful to know the code is based on the main linux distribution. I saw 
the stuff about 'hats' and noted that linux dedicates i2c0 for dealing with 
the eproms - I actually need to use that I/F so I don't need or want the 
functionality to generate overlays on the fly.

Dave