On Mon, Jun 8, 2015 at 11:34 PM, Christoph Hellwig [off-list ref] wrote:

On Mon, Jun 01, 2015 at 08:14:35PM -0400, Dan Williams wrote:

quoted

Most discovery/configuration of the libnvdimm-subsystem is done via
sysfs attributes.  However, some libnvdimm buses, particularly the
ACPI.NFIT bus, define a small set of messages that can be passed to the
platform.  For convenience we derive the initial libnvdimm-ioctl command
formats directly from the NFIT DSM Interface Example formats.

Why not merge these into the extensive sysfs interface?

Data payload size for one, these commands transfer more than a page
worth of data at a time.

Even if we killed the ioctl interface to userspace we still need all
the ugly data marshaling code in the kernel to craft properly
formatted ACPI _DSM messages.  I try to share as much common
infrastructure from the ACPI _DSM implementation to the ioctl
interface (nd_cmd_dimm_desc() + nd_cmd_bus_desc()).