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From:   Dan Williams <dan.j.williams@intel.com>
Date:   Mon, 26 Nov 2018 10:08:12 -0800
Message-ID: <CAPcyv4hVFMvut9+Rq7G41yyKzV072U33YEeHNh160VBr3QW-nw@mail.gmail.com>
Subject: Re: [PATCH 0/7] ACPI HMAT memory sysfs representation
To:     Dave Hansen <dave.hansen@intel.com>
Cc:     anshuman.khandual@arm.com, Keith Busch <keith.busch@intel.com>,
        Linux Kernel Mailing List <linux-kernel@vger.kernel.org>,
        Linux ACPI <linux-acpi@vger.kernel.org>,
        Linux MM <linux-mm@kvack.org>,
        Greg KH <gregkh@linuxfoundation.org>,
        "Rafael J. Wysocki" <rafael@kernel.org>
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On Mon, Nov 26, 2018 at 8:42 AM Dave Hansen <dave.hansen@intel.com> wrote:
>
> On 11/23/18 1:13 PM, Dan Williams wrote:
> >> A new system call makes total sense to me.  I have the same concern
> >> about the completeness of what's exposed in sysfs, I just don't see a
> >> _route_ to completeness with sysfs itself.  Thus, the minimalist
> >> approach as a first step.
> > Outside of platform-firmware-id to Linux-numa-node-id what other
> > userspace API infrastructure does the kernel need to provide? It seems
> > userspace enumeration of memory attributes is fully enabled once the
> > firmware-to-Linux identification is established.
>
> It would be nice not to have each app need to know about each specific
> platform's firmware.

The app wouldn't need to know if it uses a common library. Whether the
library calls into the kernel or not is an implementation detail. If
it is information that only the app cares about and the kernel does
not consume, why have a syscall?