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

[Charles Machalow]

On Thu, Oct 31, 2019, 6:39 AM Christoph Hellwig <hch@xxxxxx> wrote

> 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.

Not quite sure what you mean by check for zero in the ioctl handler. I
like the idea of being able to use the same struct for either the
original or 64 ioctls from userspace. I don't believe adding the
explicit rsvd field allows that

- Charlie Scott Machalow

On Thu, Oct 31, 2019 at 6:39 AM Christoph Hellwig <hch@xxxxxx> wrote:
>
> 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.