Re: Scatter-gather list constraints

[Andi Kleen <andi@firstfloor.org>]

Alan Stern <stern@rowland.harvard.edu> writes:

> This question arises in connection with wireless USB mass-storage
> devices.  The controller driver requires that all DMA segments
> in a transfer, other than the last one, have a multiple of 1024 bytes.  
> But we're sometimes getting s-g lists where an element contains an odd
> number of 512-byte sectors, and of course it doesn't work.

But you can handle a single 512 byte request? Splitting the request
in this case should work. Or maybe copying is cheaper than splitting?

I don't think the block layer knows about such kinds of restrictions.

-Andi