159 lines
2.6 KiB
HTML
159 lines
2.6 KiB
HTML
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>SG_SET_FORCE_LOW_DMA</TITLE
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>Chapter 8. Ioctl()s</TD
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NAME="S_LOWDMA">8.7. SG_SET_FORCE_LOW_DMA</H1
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CLASS="FORMALPARA"
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><P
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><B
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>SG_SET_FORCE_LOW_DMA 0x2279. </B
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>Assumes 3rd argument points to an int containing 0 or 1. 0 (default)
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means sg decides whether to use memory above 16 Mbyte level (on i386)
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based on the host adapter being used by this SCSI device. Typically
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PCI SCSI adapters will indicate they can DMA to the whole 32 bit address
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space.
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If 1 is given then the host adapter is overridden and only memory below
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the 16MB level is used for DMA. A requirement for this should be
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extremely rare. If the "reserved" buffer allocated on open() is not in
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use then it will be de-allocated and re-allocated under the 16MB level
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(and the latter operation could fail yielding ENOMEM).
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Only the current file descriptor is affected.</P
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