On Wed, 2 Jun 1999 20:18:27 +0200 (MET DST), Gerard Roudier
<groudier@club-internet.fr> said:
> Thanks, Stephen, for your raw-io patch.
> It does work, but refuses to work for me with non sector-size aligned
> buffer address.
That's correct: this is expected behaviour for Unix raw character
devices. You are doing dma from memory to disk, so the application
needs to do the alignment normally done by the OS.
> If the IO is broken into several ones, perhaps this condition would
> be required, but it seems to me that only the total IO length has to
> be a multiple of the sector-size.
You might be talking to a device which cannot scatter-gather, or which
can scatter-gather only on block boundaries. Remember that the
virtual memory is not going to be physically contiguous.
> I have implemented recently the support of unaligned Wide Transfers in the
> sym53c8xx driver and I need something that provides some oddly aligned
> buffers to test the driver code. If it is possible to remove the checking
> of buffer alignment in your code without serious breakage,
It will break the code, since there is absolutely no support anywhere
in the kernel for submitting an IO to a single disk block from a
scatter-gather buffer.
--Stephen
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