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authorDan Williams <dan.j.williams@intel.com>2008-02-02 19:49:57 -0700
committerDan Williams <dan.j.williams@intel.com>2008-02-06 10:12:17 -0700
commit0036731c88fdb5bf4f04a796a30b5e445fc57f54 (patch)
tree66982e4a9fdb92fedadca35c0ccaa0b9a75e9d2e /drivers/dma/Kconfig
parentd909b347591a23c5a2c324fbccd4c9c966f31c67 (diff)
async_tx: kill tx_set_src and tx_set_dest methods
The tx_set_src and tx_set_dest methods were originally implemented to allow an array of addresses to be passed down from async_xor to the dmaengine driver while minimizing stack overhead. Removing these methods allows drivers to have all transaction parameters available at 'prep' time, saves two function pointers in struct dma_async_tx_descriptor, and reduces the number of indirect branches.. A consequence of moving this data to the 'prep' routine is that multi-source routines like async_xor need temporary storage to convert an array of linear addresses into an array of dma addresses. In order to keep the same stack footprint of the previous implementation the input array is reused as storage for the dma addresses. This requires that sizeof(dma_addr_t) be less than or equal to sizeof(void *). As a consequence CONFIG_DMADEVICES now depends on !CONFIG_HIGHMEM64G. It also requires that drivers be able to make descriptor resources available when the 'prep' routine is polled. Signed-off-by: Dan Williams <dan.j.williams@intel.com> Acked-by: Shannon Nelson <shannon.nelson@intel.com>
Diffstat (limited to 'drivers/dma/Kconfig')
-rw-r--r--drivers/dma/Kconfig1
1 files changed, 1 insertions, 0 deletions
diff --git a/drivers/dma/Kconfig b/drivers/dma/Kconfig
index c46b7c219ee9..a703deffb795 100644
--- a/drivers/dma/Kconfig
+++ b/drivers/dma/Kconfig
@@ -5,6 +5,7 @@
menuconfig DMADEVICES
bool "DMA Engine support"
depends on (PCI && X86) || ARCH_IOP32X || ARCH_IOP33X || ARCH_IOP13XX
+ depends on !HIGHMEM64G
help
DMA engines can do asynchronous data transfers without
involving the host CPU. Currently, this framework can be