Re: [PATCH v5 05/21] libnvdimm: control (ioctl) messages for libnvdimm bus and dimm devices

[Dan Williams]

On Mon, Jun 8, 2015 at 11:34 PM, Christoph Hellwig <hch@xxxxxx> wrote:
> On Mon, Jun 01, 2015 at 08:14:35PM -0400, Dan Williams wrote:
>> 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()).
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