[uClinux-dev] nios2: how to update broken references to "sg->page"?

[Robert P. J. Day]

  ok, i'm definitely going to need some guidance on this one.  having
resolved several build errors for nios2 under the absolutely latest
kernel tree, i'm now looking at this one:

  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'
... snip more of the same ...

  well, that's not surprising, since the 2.6.23+ "struct scatterlist"
definition no longer has a "page" member, but looks more like this
(this is what i've replaced it with, it might or might not be totally
correct):

==============================================
#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;     <-- used to be "page"
        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 */
============================================

  and about that new "page_link" member, well, the header file
include/linux/scatterlist.h explains it thusly:

/*
 * Notes on SG table design.
 *
 * Architectures must provide an unsigned long page_link field in the
 * scatterlist struct. We use that to place the page pointer AND encode
 * information about the sg table as well. The two lower bits are reserved
 * for this information.
 *
 * If bit 0 is set, then the page_link contains a pointer to the next sg
 * table list. Otherwise the next entry is at sg + 1.
 *
 * If bit 1 is set, then this sg entry is the last element in a list.
 *
 * See sg_next().
 *
 */

  long story short, i have to figure out how to update the
nios2-specific source file arch/nios2nommu/mm/dma-noncoherent.c to
use the new scatterlist struct.  i'm going to start reading up on
this, but if someone has a quick fix to that file, i'm all ears.

rday

p.s.  not surprisingly, that redefinition of the scatterlist structure
might affect other architectures as well if they've hard-coded
references to "sg->page" anywhere.

-- 
========================================================================
Robert P. J. Day
Linux Consulting, Training and Annoying Kernel Pedantry
Waterloo, Ontario, CANADA

http://crashcourse.ca
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