On Thu, Jul 22, 2021 at 11:55:58PM +0100, Wedson Almeida Filho wrote:

On Thu, Jul 08, 2021 at 01:58:32AM +0100, Matthew Wilcox wrote:

quoted

A simple NVMe driver is less than a thousand lines of C.
I know the one in the kernel now is ridiculously complicated and has
been thoroughly messed up with abstractions to support NVMeoF instead
of having a separate driver, but it's really a simple interface at heart.

The latest NVMe spec is 452 pages long, which seems to contradict your claim
that it's simple. In any case, translating less than 1K lines of C shouldn't be
too hard (after I've built the abstractions, of course). Would you mind sharing
the simple driver you mention above?

You can use the 1.0 spec, which is much shorter. A 1.0 capable driver
should be forward compatible with newer devices, too.

The current nvme driver became less simple since blk-mq integration and
has only gotten more complicated since then with other transports and
more advanced features. For a simpler example, you can reference an in
kernel version <= 3.16, and ignore the "nvme-scsi" parts.