Re: [PATCH 0/4] Mac IOP driver fixes

[Finn Thain <fthain@telegraphics.com.au>]

On Sun, 31 May 2020, Brad Boyer wrote:

> 
> The swim_iop driver was never completed. As far as I know, the data 
> transfer code was never written. I remember testing the driver, and all 
> it could do was detect the drives and do eject. Read and write were not 
> working. I looked into it at the time, but it's a little messy and is 
> much more complicated than the ADB driver. For ADB, the data is small 
> enough that it's packed in the IOP message. That's not possible for 
> SWIM, so it has a more complex data handling method. If you look at the 
> code of that driver and the messages, it looks like the IOP can do DMA 
> but it can't. The SWIM IOP message includes a buffer pointer, but the 
> IOP chip isn't connected in a way that it can just access it (and it's 
> getting passed a virtual address anyway). Based on some of the other 
> information I was given, there's a separate message protocol on channel 
> 0 (on each IOP) for bulk data transfer.
> 
> At the time, I had a diff to fix some bugs in the detection and handle 
> the status update messages. However, it hardly seemed worth submitting 
> that as a fix since the driver still wasn't useful without the bulk data 
> transfer working. I can pass my diff along if you intend to make an 
> attempt at a working swim_iop driver.
> 

I'm hoping that the SWIM IOP can be used in bypass mode, so it could be 
used with the swim.c driver. I haven't been able to make that work yet.

You may want to send the patch to the mailing list anyway. Or maybe send 
it to the linux-mac68k bug tracker on sourceforge.