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    Subject[PATCH 4/7] sg_ring: dma_map_sg_ring() helper
    Date
    Obvious counterpart to dma_map_sg.  Note that this is arch-independent
    code; sg_rings are backwards compatible with simple sg arrays.

    Signed-off-by: Rusty Russell <rusty@rustcorp.com.au>
    ---
    drivers/base/dma-mapping.c | 13 +++++++++++++
    include/linux/dma-mapping.h | 4 ++++
    2 files changed, 17 insertions(+), 0 deletions(-)

    diff --git a/drivers/base/dma-mapping.c b/drivers/base/dma-mapping.c
    --- a/drivers/base/dma-mapping.c
    +++ b/drivers/base/dma-mapping.c
    @@ -8,6 +8,7 @@
    */

    #include <linux/dma-mapping.h>
    +#include <linux/sg_ring.h>

    /*
    * Managed DMA API
    @@ -162,6 +163,59 @@ void dmam_free_noncoherent(struct device
    }
    EXPORT_SYMBOL(dmam_free_noncoherent);

    +/**
    + * dma_map_sg_ring - Map an entire sg ring
    + * @dev: Device to free noncoherent memory for
    + * @sg: The sg_ring
    + * @direction: DMA_TO_DEVICE, DMA_FROM_DEVICE or DMA_BIDIRECTIONAL.
    + *
    + * This returns -ENOMEM if mapping fails. It's not clear that telling you
    + * it failed is useful though.
    + */
    +int dma_map_sg_ring(struct device *dev, struct sg_ring *sg,
    + enum dma_data_direction direction)
    +{
    + struct sg_ring *i;
    + unsigned int num;
    +
    + for (i = sg; i; i = sg_ring_next(i, sg)) {
    + BUG_ON(i->num > i->max);
    + num = dma_map_sg(dev, i->sg, i->num, direction);
    + if (num == 0 && i->num != 0)
    + goto unmap;
    + }
    + return 0;
    +
    +unmap:
    + while (sg) {
    + dma_unmap_sg(dev, sg->sg, sg->num, direction);
    + sg = sg_ring_next(sg, i);
    + }
    + return -ENOMEM;
    +
    +}
    +EXPORT_SYMBOL(dma_map_sg_ring);
    +
    +/**
    + * dma_unmap_sg_ring - Unmap an entire sg ring
    + * @dev: Device to free noncoherent memory for
    + * @sg: The sg_ring
    + * @direction: DMA_TO_DEVICE, DMA_FROM_DEVICE or DMA_BIDIRECTIONAL.
    + *
    + * Call after dma_map_sg_ring() succeeds.
    + */
    +void dma_unmap_sg_ring(struct device *dev, struct sg_ring *sg,
    + enum dma_data_direction direction)
    +{
    + struct sg_ring *i;
    +
    + for (i = sg; i; i = sg_ring_next(i, sg)) {
    + BUG_ON(i->num > i->max);
    + dma_unmap_sg(dev, i->sg, i->num, direction);
    + }
    +}
    +EXPORT_SYMBOL(dma_unmap_sg_ring);
    +
    #ifdef ARCH_HAS_DMA_DECLARE_COHERENT_MEMORY

    static void dmam_coherent_decl_release(struct device *dev, void *res)
    diff --git a/include/linux/dma-mapping.h b/include/linux/dma-mapping.h
    --- a/include/linux/dma-mapping.h
    +++ b/include/linux/dma-mapping.h
    @@ -87,6 +87,12 @@ dma_mark_declared_memory_occupied(struct
    }
    #endif

    +struct sg_ring;
    +extern int dma_map_sg_ring(struct device *dev, struct sg_ring *sg,
    + enum dma_data_direction direction);
    +extern void dma_unmap_sg_ring(struct device *dev, struct sg_ring *sg,
    + enum dma_data_direction direction);
    +
    /*
    * Managed DMA API
    */

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