ok, i think i have this figured out. the current build error for a
nios2 kernel:
...
CC arch/nios2nommu/mm/dma-noncoherent.o
arch/nios2nommu/mm/dma-noncoherent.c: In function `dma_map_sg':
arch/nios2nommu/mm/dma-noncoherent.c:139: error: structure has no member named
`page'
arch/nios2nommu/mm/dma-noncoherent.c:142: error: structure has no member named
`page'
arch/nios2nommu/mm/dma-noncoherent.c: In function `dma_unmap_sg':
arch/nios2nommu/mm/dma-noncoherent.c:194: error: structure has no member named
`page'
arch/nios2nommu/mm/dma-noncoherent.c: In function `dma_sync_sg_for_cpu':
arch/nios2nommu/mm/dma-noncoherent.c:263: error: structure has no member named
`page'
arch/nios2nommu/mm/dma-noncoherent.c: In function `dma_sync_sg_for_device':
arch/nios2nommu/mm/dma-noncoherent.c:278: error: structure has no member named
`page'
make[2]: *** [arch/nios2nommu/mm/dma-noncoherent.o] Error 1
make[1]: *** [arch/nios2nommu/mm] Error 2
make[1]: Leaving directory
`/home/rpjday/nios2/uclinux/uClinux-dist-cvs/linux-2.6.x'
make: *** [linux] Error 1
$
that's because a "struct sg" doesn't have a simple "page" member
anymore, it has a "page_link" member which allows "sg" structs to not
be consecutive. that means that, when you iterate through a list of
"struct sg"s, it's not enough to just keep incrementing the current
pointer, as in "sg++", as it's doing in the current source file
arch/nios2nommu/mm/dma-noncoherent.c (here's one example):
for (i = 0; i < nents; i++, sg++) {
unsigned long addr;
addr = (unsigned long) page_address(sg->page);
if (addr) {
__dma_sync(addr + sg->offset, sg->length, direction);
sg->dma_address = (dma_addr_t)page_to_phys(sg->page)
+ sg->offset;
}
}
see how that just assumes that all sg's are consecutive? but you
can't assume that anymore. happily, the current header file
include/linux/scatterlist.h takes care of that with an iterator
definition:
/*
* Loop over each sg element, following the pointer to a new list if necessary
*/
#define for_each_sg(sglist, sg, nr, __i) \
for (__i = 0, sg = (sglist); __i < (nr); __i++, sg = sg_next(sg))
and it's that "sg_next(sg)" macro that automatically handles either
a simple iteration, or following the pointer, so any sg iterator loops
should be re-coded to use the newer macro. note that those new
macros are fully backward-compatible, so just changing the way
iteration is done should work just fine with older code.
of course, i've been wrong before.
rday
p.s. obviously, the include/asm-nios2nommu/scatterlist.h header file
has to be updated to match the new scatterlist definition as well.
this is what i've got now, just FYI:
==============================
#ifndef __ASM_NIOS2_SCATTERLIST_H
#define __ASM_NIOS2_SCATTERLIST_H
struct scatterlist {
#ifdef CONFIG_DEBUG_SG
unsigned long sg_magic;
#endif
unsigned long page_link;
unsigned int offset;
dma_addr_t dma_address;
unsigned int length;
};
#define ISA_DMA_THRESHOLD (0xffffffff)
#define sg_dma_address(sg) (virt_to_bus((sg)->dma_address))
#define sg_dma_len(sg) ((sg)->length)
#endif /* __ASM_NIOS2_SCATTERLIST_H */
==================================
--
========================================================================
Robert P. J. Day
Linux Consulting, Training and Annoying Kernel Pedantry
Waterloo, Ontario, CANADA
http://crashcourse.ca
========================================================================
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