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The Documentation/DMA-API-HOWTO.txt states that the dma_map_sg() function
returns the number of the created entries in the DMA address space.
However the subsequent calls to the dma_sync_sg_for_{device,cpu}() and
dma_unmap_sg must be called with the original number of the entries
passed to the dma_map_sg().
struct sg_table is a common structure used for describing a non-contiguous
memory buffer, used commonly in the DRM and graphics subsystems. It
consists of a scatterlist with memory pages and DMA addresses (sgl entry),
as well as the number of scatterlist entries: CPU pages (orig_nents entry)
and DMA mapped pages (nents entry).
It turned out that it was a common mistake to misuse nents and orig_nents
entries, calling DMA-mapping functions with a wrong number of entries or
ignoring the number of mapped entries returned by the dma_map_sg()
function.
To avoid such issues, lets use a common dma-mapping wrappers operating
directly on the struct sg_table objects and use scatterlist page
iterators where possible. This, almost always, hides references to the
nents and orig_nents entries, making the code robust, easier to follow
and copy/paste safe.
Signed-off-by: Marek Szyprowski <m.szyprowski@samsung.com>
Acked-by: Juergen Gross <jgross@suse.com>
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| events | ||
| xen-pciback | ||
| xenbus | ||
| xenfs | ||
| acpi.c | ||
| arm-device.c | ||
| balloon.c | ||
| biomerge.c | ||
| cpu_hotplug.c | ||
| dbgp.c | ||
| efi.c | ||
| evtchn.c | ||
| features.c | ||
| gntalloc.c | ||
| gntdev-common.h | ||
| gntdev-dmabuf.c | ||
| gntdev-dmabuf.h | ||
| gntdev.c | ||
| grant-table.c | ||
| Kconfig | ||
| Makefile | ||
| manage.c | ||
| mcelog.c | ||
| mem-reservation.c | ||
| pci.c | ||
| pcpu.c | ||
| platform-pci.c | ||
| privcmd-buf.c | ||
| privcmd.c | ||
| privcmd.h | ||
| pvcalls-back.c | ||
| pvcalls-front.c | ||
| pvcalls-front.h | ||
| swiotlb-xen.c | ||
| sys-hypervisor.c | ||
| time.c | ||
| xen-acpi-cpuhotplug.c | ||
| xen-acpi-memhotplug.c | ||
| xen-acpi-pad.c | ||
| xen-acpi-processor.c | ||
| xen-balloon.c | ||
| xen-front-pgdir-shbuf.c | ||
| xen-scsiback.c | ||
| xen-stub.c | ||
| xlate_mmu.c | ||