This is in no way specific to mach64, so I would appreciate if someone
could help on this.
I would like to read the contents of a DMA buffer in a DRM IOCTL to
process it with MMIO. Initialy I thought that "buf->address" gave me the
pointer to that but after some debuggin output I saw that "buf->address"
has the same info than "buf->offset",
<7>[drm:mach64_dma_vertex] mach64_dma_vertex: pid=1471 index=0
count=560 discard=1
<7>[drm:mach64_dma_dispatch_vertex] mach64_dma_dispatch_vertex:
buf=0 nbox=0
<6>[drm] idx = 0, offset=0xe0000000, address=0xe0000000, used=560
^^^^^^^^^^ ^^^^^^^^^^
|||||||||| ||||||||||
and in fact both are given the same value in the presence of AGP-GART
(drm_bufs.h:400):
buf->bus_address = agp_offset + offset;
buf->address = (void *)(agp_offset + offset);
although I noticed that with PCI-GART and plain PCI they are done
differently.
So what is the general approach to get a valid C pointer to a DMA buffer?
Regards,
José Fonseca
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