Re: [PATCH] nvme: change nvme_passthru_cmd64's result field.

[Christoph Hellwig]

On Wed, Oct 30, 2019 at 10:03:38PM -0700, Charles Machalow wrote:
> Changing nvme_passthru_cmd64's result field to be backwards compatible
> with the nvme_passthru_cmd/nvme_admin_cmd struct in terms of the result
> field. With this change the first 32 bits of result in either case
> point to CQE DW0. This allows userspace tools to use the new structure
> when using the old ADMIN/IO_CMD ioctls or new ADMIN/IO_CMD64 ioctls.

All that casting is a pretty bad idea.  please just add an explicit
reserved field before the result, and check that it always is zero
in the ioctl handler.