[PATCH v4 2/6] block: Add Sed-opal library

[Scott Bauer]

On Sun, Jan 08, 2017 at 06:05:07AM -0800, Christoph Hellwig wrote:
> On Thu, Dec 29, 2016 at 12:26:51PM -0700, Scott Bauer wrote:
> 
> > +	cmd->cmd = cmd->cmd_buf;
> > +	cmd->resp = cmd->resp_buf;
> > +
> > +	dma_align = (queue_dma_alignment(q) | q->dma_pad_mask) + 1;
> > +	cmd->cmd = (u8 *)round_up((uintptr_t)cmd->cmd, dma_align);
> > +	cmd->resp = (u8 *)round_up((uintptr_t)cmd->resp, dma_align);
> 
> The block layer will automatically bounce buffer non-aligned payloads.
> If the cost of copying is too high we could switch back to dynamic
> allocations using kmalloc here, which will be properly aligned.
> 
> Also ->cmd and ->resp probably should be void pointers, so that no
> casting is required for the various command and response structures.

We'll keep it unaligned and let the block layer deal with it. I had
previously toyed with the void pointers, but we reference directly into
cmd->cmd[] during command setup. So while we'll avoid a cast here we'll
end up adding more code/casts to other functions, so I'm going to leave
it as is in the series coming out in an hour or so.