Re: [PATCH] libnvdimm: clean up command definitions

From: Dan Williams <dan.j.williams@intel.com>
To: Yasunori Goto <y-goto@jp.fujitsu.com>
Cc: Jerry Hoemann <Jerry.Hoemann@hpe.com>,
	"linux-nvdimm@lists.01.org" <linux-nvdimm@lists.01.org>,
	"linux-kernel@vger.kernel.org" <linux-kernel@vger.kernel.org>
Subject: Re: [PATCH] libnvdimm: clean up command definitions
Date: Mon, 28 Aug 2017 20:22:09 -0700	[thread overview]
Message-ID: <CAPcyv4jp5Q9XZ=ZEp=NvUgJyh+zYoDTOGy=+4ETLjX2RDvAg-w@mail.gmail.com> (raw)
In-Reply-To: <20170829100344.C729.E1E9C6FF@jp.fujitsu.com>

On Mon, Aug 28, 2017 at 6:03 PM, Yasunori Goto <y-goto@jp.fujitsu.com> wrote:
>> On Mon, Aug 28, 2017 at 1:50 PM, Jerry Hoemann <jerry.hoemann@hpe.com> wrote:
>> >
>> > On Mon, Aug 28, 2017 at 08:45:32AM -0700, Dan Williams wrote:
>> >> Remove the command payloads that do not have an associated libnvdimm
>> >> ioctl. I.e. remove the payloads that would only ever be carried in the
>> >> ND_CMD_CALL envelope. This prevents userspace from growing unnecessary
>> >> dependencies on this kernel header when userspace already has everything
>> >> it needs to craft and send these commands.
>> >
>> > Userspace needs to include linux/ndctl.h to make the call as
>> > that is where nd_cmd_pkg is defined.
>> >
>> > So you want to have some structures defined in ndctl.h and other
>> > defined in the to be created libndctl-nfit.h?  Plus a third header
>> > file for the HPE non-root calls?
>>
>> Yes. ndctl.h exports the ioctl command payloads, everything that goes
>> inside of ND_CMD_CALL is defined by userspace headers. The
>> libndctl-nfit.h header is proposed as a place to land vendor agnostic
>> NFIT-defined payloads, and any vendor specific definitions would
>> remain internal to libndctl as they are today.
>>
>> > Will libndctl-nfit.h be generally available and installed?
>>
>> Yes, that's the plan.
>>
>> > Will it be clean so that other applications can use it to get these
>> > definitions?  Or will it be loaded w/ a bunch of stuff only useful
>> > to your ndctl command?
>>
>> Yes, that's the plan. It's a bug if libndctl-nfit.h is not generically
>> clean for issuing the NFIT root device commands via some ND_CMD_CALL
>> helpers from the base libndctl library.
>>
>> In other words libndctl-nfit.h defines the payload and libndctl
>> defines some general helpers for issuing commands.
>
> Maybe I don't understand your idea yet, let me confirm it.
>
> Certainly, current acpi driver does not need these definitions.
> But, I think nfit_test.ko will need them to emulate these features.
>
> Do you intend that libndctl-nfit.h should be defined at "include/uapi/linux/"
> directory?
> Otherwise, it should be defined at "tools/testing/nvdimm/" or
> "tools/testing/nvdimm/test" ?

nfit_test will need its own internal / private copy of these payloads
in tools/testing/nvdimm/test so it can emulate how the bios behaves.
The include/uapi/linux directory is for user to kernel interface
definitions and these command payloads are purely an interface to bios
/ firmware.