Clockport devices configuration layer [was: Re: USB stack vs bus_dma_tag_t]

[Radek Kujawa <radoslaw.kujawa%c0ff33.net@localhost>]

Wiadomość napisana w dniu 2010-10-13, o godz. 14:36, przez Frank Wille:
> > Can it be easily glued together to provide what I need? Ofcourse that
> > would not bring proper DMA handling to amiga port, because it needs
> > far more MD code.
>
> When you look at mac68k you just need to define a m68k_bus_dma_tag in
> mainbus.c and pass the tag to all attached devices. The dma functions
> are all defined in m68k/m68k/bus_dma.c.


I already hacked contents of m68k bus_dma.h into amiga bus.h. It was  
enough for USB stack to compile. I'll look into bus_dma  
implementations of other ports later. Though, I would prefer not to  
mess with it - I don't really understand what is going on in this code.

SUBWAY driver is slowly progressing. I have probe prototype working:
http://c0ff33.net/~rkujawa/subway-probe.txt
It is quite nice, because due to design of SUBWAY it does not need any  
writes to bus, only series of reads. So I think it would be okay to  
include driver even in GENERIC kernel.

Speaking of GENERIC kernel. Current autoconf mechanism in amiga port  
does not work well for clockport cards. Now we can either attach to  
mainbus by means of autoconf.c (really ugly for anything but  
mainboards devices), or by zbus which is fine for real Zorro cards,  
but not for clockport stuff.

There's one problem that makes writing drivers for clockport devices  
difficult. Clockport is available on many base addresses, and address  
depends on physical location of clockport. A1200 mainboard clockport  
has different address than X-Surf clockport, different than ZIV  
busboard clockport, etc. etc. In current situation, handling this is  
up to person developing the device driver. SUBWAY driver should work  
on original clockport and various Zorro clockports. But I don't want  
to probe all these posible locations inside of my driver... And  
tomorrow someone may create clockport on other base address.

I propose that we (read: mostly I) implement thin abstration layer,  
that would simplify writing clockport cards drivers. Clockport layer  
would provide information on base address to the device driver. It  
could be configured manually, by setting base address in config file,  
or automatically by matching known clockport carrier at zbus.

Configuration file could look like this:

clockport0 at mainbus addr 0xd80000 # A1200 mainboard clockport
clockport* at zbus? # various Zorro clockports
tduhc0 at clockport? # E3B SUBWAY USB Controller

If someone bought unofficial clockport adapter (like A603, CPU  
clockport adapter), that does use other base address, he could just  
change address in config file. No changes to the driver required!  
Ofcourse, all of this is against amiga idea of autoconfiguration, but  
so are clockport cards.

Best regards,
Radoslaw Kujawa