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Fwd: USB stack vs bus_dma_tag_t
I already posted following message to port-amiga, but comment on this matter
from USB wizard would be appreciated. I'm mostly interested in how complete
bus_dma implementation must be for USB stack to work (provided I'm not doing
any real DMA transfers).
----- Forwarded message from Radek Kujawa -----
Date: Sun, 10 Oct 2010 08:30:56 +0200
Subject: USB stack vs bus_dma_tag_t
Yesterday evening I tried to compile kernel for Amiga with USB stack
included. I stumbed upon following error:
# compile A1200DEV/uhub.o
In file included from /Users/rkujawa/NetBSD-src/src/sys/dev/usb/uhub.c:53:
/Users/rkujawa/NetBSD-src/src/sys/dev/usb/usbdivar.h:123: error: expected
specifier-qualifier-list before 'bus_dma_tag_t'
Brief look at the source gave me impression that:
- Amiga port of NetBSD does not support MI DMA machinery
- There's bus_dma_tag_t in arch/m68k but not in arch/amiga
- USB stack thinks that every port is capable of MI DMA
- USB stack thinks that every driver does DMA transfers
I don't need real implementation of bus_dma, as SUBWAY is not a DMA controller
anyway. I just need the data structures for USB stack. DMA transfers can be
faked by driver, it was already done in SL811HS driver. Albeit this looks ugly
and proper solution would be introduction of non-DMA Host Controller concept to
USB stack. Requirement of bus_dma structures must stay in USB stack anyway,
because there are DMA controllers that need it.
How does bus_dma implementation of arch/m68k relate to arch/amiga? 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.
----- End forwarded message -----
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