Re: [PATCH v9] block: Add n64 cart driver

Lauri Kasanen
2021-01-22T17:08:10Z

On Fri, 22 Jan 2021 16:39:13 +0000
Christoph Hellwig <hch@infradead.org> wrote:

> On Fri, Jan 22, 2021 at 06:23:49PM +0200, Lauri Kasanen wrote:
> > > Your driver can communicate the required alignment using the
> > > blk_queue_update_dma_alignment API.
> >
> > Is it guaranteed to be physically contiguous?
>
> The alignment requirement applies to each bio_vec.
>
> What alignment does the hardware require?

It requires 8-byte alignment, but the buffer must also be physically
contiguous.

I grepped around, but apparently no driver under drivers/block does
direct DMA to the bio buffer. They all use their own buffer and memcpy,
like this patch. ps3vram, ps3disk, amiflop, etc etc.

If all existing drivers use their own buffer, why is a different
approach required for new drivers?

- Lauri