linux-kernel - Re: [PATCH 2/3] acpi, nfit: add dimm device notification support

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Date:   Fri, 26 Aug 2016 11:39:23 -0700
From:   Dan Williams <dan.j.williams@...el.com>
To:     "Kani, Toshimitsu" <toshi.kani@....com>
Cc:     "linux-nvdimm@...ts.01.org" <linux-nvdimm@...ts.01.org>,
        "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
        "linux-acpi@...r.kernel.org" <linux-acpi@...r.kernel.org>,
        "Wysocki, Rafael J" <rafael.j.wysocki@...el.com>
Subject: Re: [PATCH 2/3] acpi, nfit: add dimm device notification support

On Fri, Aug 26, 2016 at 11:26 AM, Kani, Toshimitsu <toshi.kani@....com> wrote:
> On Tue, 2016-08-23 at 14:54 -0700, Dan Williams wrote:
>> Per "ACPI 6.1 Section 9.20.3" NVDIMM devices, children of the
>> ACPI0012 NVDIMM Root device, can receive health event notifications.
>>
>> Given that these devices are precluded from registering a
>> notification handler via acpi_driver.acpi_device_ops (due to no
>> _HID), we use acpi_install_notify_handler() directly.
>
> I've confirmed that this ACPI notify handler is called properly.
>
>> The registered handler, acpi_nvdimm_notify(), triggers a poll(2)
>> event on the nmemX/nfit/flags sysfs attribute when a health event
>> notification is received.
>
> This sounds good idea, but should we document that the value of sysfs
> 'flags' itself does not get updated?  User space program will then need
> to call its _DSM to get health status.

Yes, this plus the new scrub attribute behavior need documentation.
I'll prepare a refresh for Documentation/nvdimm/nvdimm.txt.

The need to call a _DSM after a notification event is documented in
the ACPI spec, but you're right, we do need to connect that language
to the Linux specific mechanism.