On Thu, May 08, 2003 at 03:16:22PM -0700, Rick Smith wrote:
> What are the memory address restrictions when using the O_DIRECT flag
> with XFS? I am trying to perform I/O directly from the filesystem to a
> piece of mmap'ed video memory and I get the "bad address" error when I
> attempt to do so with O_DIRECT. Without the O_DIRECT flag I am able to
> perform the I/O but is it must too slow. Using O_DIRECT with other system
> memory seems to work fine, but I would like the option of transferring data
> directly to a video card without a bounce buffer and a DMA step. Is direct
> I/O available to any memory address that satisfies the alignment
> requirement or must this address be below the MAX_DMA_ADDR?
The only restriction is that the base address and the size must be an
multiply of the block size of the file system (normally 4K)
-Andi
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