Question about dma_direct_ops in PowerPC.

[Fushen Chen]

We have a board with PCI device driver that calls for
pci_dma_sync_single_for_device.
This driver used to work for Linux kernel 2.6.25.

We ported to the driver to Linux kernel 2.6.32. The PCI device driver
doesn't work anymore.
The following call trace shows why the PCI driver won't work in kernel
2.6.32.
1. In pci_include/asm-generic/pci-dma-compat.h
    pci_dma_sync_single_for_device calls for dma_sync_single_for_cpu
2. In include/asm-generic/dma-mapping-common.h
    dma_sync_single_for_cpu calls for ops->sync_single_for_cpu
3. In arch/powerpc/kernel/dma.c
struct dma_map_ops dma_direct_ops = {
        .alloc_coherent = dma_direct_alloc_coherent,
        .free_coherent  = dma_direct_free_coherent,
        .map_sg         = dma_direct_map_sg,
        .unmap_sg       = dma_direct_unmap_sg,
        .dma_supported  = dma_direct_dma_supported,
        .map_page       = dma_direct_map_page,
        .unmap_page     = dma_direct_unmap_page,
#ifdef CONFIG_NOT_COHERENT_CACHE
        .sync_single_range_for_cpu      = dma_direct_sync_single_range,
        .sync_single_range_for_device   = dma_direct_sync_single_range,
        .sync_sg_for_cpu                = dma_direct_sync_sg,
        .sync_sg_for_device             = dma_direct_sync_sg,
#endif
};
There is no ops defined for sync_single_for_cpu.
The pci_dma_sync_single_for_device is a no-op.

However Linux kernel 2.6.35.1 from kernel.org has the  .sync_single_for_cpu
for dma_direct_ops.
in arch/powerpc/kernel/dma.c
#ifdef CONFIG_NOT_COHERENT_CACHE
        .sync_single_for_cpu            = dma_direct_sync_single,
        .sync_single_for_device         = dma_direct_sync_single,
        .sync_sg_for_cpu                = dma_direct_sync_sg,
        .sync_sg_for_device             = dma_direct_sync_sg,
#endif


We won't move to Linux kernel 2.6.35 anytime soon.
My questions:
1. Is there any side effect for adding .sync_single_for_cpu to
dma_direct_ops in 2.6.32?
2. What will be the future development here?


Best regards & Thanks,
Fushen
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