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Date: Wed, 21 Feb 2018 15:46:06 -0800
From: Dan Williams <dan.j.williams@...el.com>
To: Aishwarya Pant <aishpant@...il.com>
Cc: "Rafael J. Wysocki" <rjw@...ysocki.net>,
Len Brown <lenb@...nel.org>, linux-nvdimm@...ts.01.org,
Linux ACPI <linux-acpi@...r.kernel.org>,
Linux Kernel Mailing List <linux-kernel@...r.kernel.org>,
Jonathan Corbet <corbet@....net>,
Greg KH <gregkh@...uxfoundation.org>,
Julia Lawall <julia.lawall@...6.fr>
Subject: Re: [PATCH] acpi: nfit: document sysfs interface
Wow, thank you for taking a look at this! Always nice to get an
unexpected documentation gift. Some comments below:
On Mon, Feb 19, 2018 at 10:07 AM, Aishwarya Pant <aishpant@...il.com> wrote:
> This is an attempt to document the nfit sysfs interface. The
> descriptions have been collected from git commit logs and the ACPI
> specification 6.2. There are still two undocumented attributes-
> range_index and ecc_unit_size, for which I couldn't collect complete
> information.
'range_index' is taken directly from the ACPI specification. It's a
unique number provided by the BIOS to identify an address range.
Here's a quote from ACPI 6.2a [1] section '5.2.25.2 System Physical
Address (SPA) Range Structure' "SPA Range Structure Index: Used by
NVDIMM Region Mapping Structure to uniquely refer to this structure.
Value of 0 is Reserved and shall not be used as an index."
'ecc_unit_size' is the size of a write request to a DIMM that will not
incur a read-modify-write cycle at the memory controller. More details
from the commit log here [2]
[1]: http://www.uefi.org/sites/default/files/resources/ACPI%206_2_A_Sept29.pdf
[2]: https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git/commit/?id=a15797f4bef
>
> Signed-off-by: Aishwarya Pant <aishpant@...il.com>
> ---
> Documentation/ABI/testing/sysfs-bus-nfit | 202 +++++++++++++++++++++++++++++++
> 1 file changed, 202 insertions(+)
> create mode 100644 Documentation/ABI/testing/sysfs-bus-nfit
>
> diff --git a/Documentation/ABI/testing/sysfs-bus-nfit b/Documentation/ABI/testing/sysfs-bus-nfit
> new file mode 100644
> index 000000000000..758d8d0d4c37
> --- /dev/null
> +++ b/Documentation/ABI/testing/sysfs-bus-nfit
> @@ -0,0 +1,202 @@
> +What: /sys/bus/nd/devices/nmemX/nfit/serial
> +Date: Apr, 2015
> +KernelVersion: v4.1
> +Contact: linux-nvdimm@...ts.01.org
> +Description:
> + (RO) Serial number of the NVDIMM (non-volatile dual in-line
> + memory module), assigned by the module vendor.
For all of these nfit/* attributes it would be helpful to include a
reference to the ACPI specification. I.e. for all of these nfit/*
attributes add a sentence "See the 'NVDIMM Firmware Interface Table
(NFIT)' section in the ACPI specification
(http://www.uefi.org/specifications) for more details.".
> +
> +
> +What: /sys/bus/nd/devices/nmemX/nfit/handle
> +Date: Apr, 2015
> +KernelVersion: v4.1
> +Contact: linux-nvdimm@...ts.01.org
> +Description:
> + (RO) The address (given by the _ADR object) of the device on its
> + parent bus of the NVDIMM device containing the NVDIMM region.
> +
> +
> +What: /sys/bus/nd/devices/nmemX/nfit/device
> +Date: Apr, 2015
> +KernelVersion: v4.1
> +Contact: linux-nvdimm@...ts.01.org
> +Description:
> + (RO) Identifier for the NVDIMM, assigned by the module vendor.
s/Identifier/Device Id/
> +
> +
> +What: /sys/bus/nd/devices/nmemX/nfit/rev_id
> +Date: Apr, 2015
> +KernelVersion: v4.1
> +Contact: linux-nvdimm@...ts.01.org
> +Description:
> + (RO) Revision of the NVDIMM, assigned by the module vendor.
> +
> +
> +What: /sys/bus/nd/devices/nmemX/nfit/phys_id
> +Date: Apr, 2015
> +KernelVersion: v4.1
> +Contact: linux-nvdimm@...ts.01.org
> +Description:
> + (RO) Handle (i.e., instance number) for the SMBIOS (system
> + management BIOS) Memory Device structure describing the NVDIMM
> + containing the NVDIMM region.
> +
> +
> +What: /sys/bus/nd/devices/nmemX/nfit/flags
> +Date: Jun, 2015
> +KernelVersion: v4.1
> +Contact: linux-nvdimm@...ts.01.org
> +Description:
> + (RO) The flags in the NFIT memory device sub-structure indicate
> + the state of the data on the nvdimm relative to its energy
> + source or last "flush to persistence".
> +
> + The attribute is a translation of the 'NVDIMM State Flags' field
> + in section 5.2.25.3 'NVDIMM Region Mapping' Structure of the
> + ACPI specification 6.2.
> +
> + The health states are "save_fail", "restore_fail", "flush_fail",
> + "not_armed", "smart_event", "map_fail" and "smart_notify".
> +
> +
> +What: /sys/bus/nd/devices/nmemX/nfit/format
> +What: /sys/bus/nd/devices/nmemX/nfit/format1
> +What: /sys/bus/nd/devices/nmemX/nfit/formats
> +Date: Apr, 2016
> +KernelVersion: v4.6
> +Contact: linux-nvdimm@...ts.01.org
> +Description:
> + (RO) Identifiers for the programming interface. Starting with
"Identifiers for one or more programming interfaces, format interface
codes, supported by the NVDIMM."
> + ACPI 6.1 an NFIT table reports multiple 'NVDIMM Control Region
> + Structure' instances per-dimm, one for each supported format
> + interface. That code is represented in the sysfs as follows:
> + nmemX/nfit/formats, nmemX/nfit/format, nmemX/nfit/format1,
> + nmemX/nfit/format2 ... nmemX/nfit/formatN, where format2 -
> + formatN are theoretical as there are no known DIMMs with support
> + for more than two interface formats.
I'd delete the above since those are kernel / specification
implementation details that don't help explain what the attribute is.
> The 'formats' attribute
> + displays the number of supported interfaces.
"The interface codes indicate support for persistent memory mapped
directly into system physical address space and / or a block aperture
access mechanism to the NVDIMM media."
> +
> + This layout is compatible with existing libndctl binaries that
> + only expect one code per-dimm as they will ignore
> + nmemX/nfit/formats and nmemX/nfit/formatN.
> +
> +
> +What: /sys/bus/nd/devices/nmemX/nfit/vendor
> +Date: Apr, 2016
> +KernelVersion: v4.6
> +Contact: linux-nvdimm@...ts.01.org
> +Description:
> + (RO) Identifier indicating the vendor of the NVDIMM.
> +
s/Identifier indicating the vendor/Vendor Id/
> +
> +What: /sys/bus/nd/devices/nmemX/nfit/dsm_mask
> +Date: Apr, 2016
> +KernelVersion: v4.6
> +Contact: linux-nvdimm@...ts.01.org
> +Description:
> + (RO) The bitmask indicates the supported device specific control
> + functions.
s/functions/functions relative to the NVDIMM command family supported
by the device./
> +
> +
> +What: /sys/bus/nd/devices/nmemX/nfit/family
> +Date: Apr, 2016
> +KernelVersion: v4.6
> +Contact: linux-nvdimm@...ts.01.org
> +Description:
> + (RO) Displays the NVDIMM family (and the command sets). Values
s/and the command sets/command set/
> + 0, 1, 2 and 3 correspond to NVDIMM_FAMILY_INTEL,
> + NVDIMM_FAMILY_HPE1, NVDIMM_FAMILY_HPE2 and NVDIMM_FAMILY_MSFT
> + respectively.
"See the specifications for these command families here:
http://pmem.io/documents/NVDIMM_DSM_Interface-V1.6.pdf
https://github.com/HewlettPackard/hpe-nvm/blob/master/Documentation/
https://msdn.microsoft.com/library/windows/hardware/mt604741"
> +
> +
> +What: /sys/bus/nd/devices/nmemX/nfit/id
> +Date: Apr, 2016
> +KernelVersion: v4.6
> +Contact: linux-nvdimm@...ts.01.org
> +Description:
> + (RO) ACPI specification 6.2 section 5.2.25.9, defines an
> + identifier for an NVDIMM, which refelects the id attribute.
> +
> + If the manufacturing location and manufacturing date fields are
> + valid, then 'id' is composed of the vendor id (bytes 0-1),
> + manufacturing location byte, manufacturing date (bytes 0-1) and
> + the serial number(bytes 0-3), otherwise it is composed of vendor
> + id (bytes 0-1) and serial number (bytes 0-3)
I'd drop this section, this first sentence that refers to the ACPI
section is enough.
> +
> +
> +What: /sys/bus/nd/devices/nmemX/nfit/subsystem_vendor
> +Date: Apr, 2016
> +KernelVersion: v4.6
> +Contact: linux-nvdimm@...ts.01.org
> +Description:
> + (RO) Vendor of the NVDIMM non-volatile memory subsystem
> + controller.
s/Vendor/Sub-system Vendor Id/
> +
> +
> +What: /sys/bus/nd/devices/nmemX/nfit/subsystem_rev_id
> +Date: Apr, 2016
> +KernelVersion: v4.6
> +Contact: linux-nvdimm@...ts.01.org
> +Description:
> + (RO) Revision of the NVDIMM non-volatile memory subsystem
> + controller, assigned by the non-volatile memory subsystem
> + controller vendor.
s/Revision/Sub-system Revision Id/
> +
> +
> +What: /sys/bus/nd/devices/nmemX/nfit/subsystem_device
> +Date: Apr, 2016
> +KernelVersion: v4.6
> +Contact: linux-nvdimm@...ts.01.org
> +Description:
> + (RO) Identifier for the NVDIMM non-volatile memory subsystem
> + controller, assigned by the non-volatile memory subsystem
> + controller vendor.
s/Identifier/Sub-system Device Id/
> +
> +
> +What: /sys/bus/nd/devices/ndbusX/nfit/revision
> +Date: Apr, 2015
> +KernelVersion: v4.1
> +Contact: linux-nvdimm@...ts.01.org
> +Description:
> + (RO) ACPI Specification minor version number.
"ACPI NFIT table revision number"
> +
> +
> +What: /sys/bus/nd/devices/ndbusX/nfit/scrub
> +Date: Sep, 2016
> +KernelVersion: v4.8
> +Contact: linux-nvdimm@...ts.01.org
> +Description:
> + (RW) This shows the number of full Address Range Scrubs (ARS)
> + that have been completed since driver load time. Userspace can
> + wait on this using select/poll etc. A '+' at the end indicates
> + an ARS is in progress
> +
> + Writing a value of 1 triggers an ARS scan.
> +
> +
> +What: /sys/bus/nd/devices/ndbusX/nfit/hw_error_scrub
> +Date: Sep, 2016
> +KernelVersion: v4.8
> +Contact: linux-nvdimm@...ts.01.org
> +Description:
> + (RW) Provides a way to toggle the behavior between just adding
> + the address (cache line) where the MCE happened to the poison
> + list and doing a full scrub. The former (selective insertion of
> + the address) is done unconditionally.
> +
> + This attribute can have the following values written to it:
> +
> + '0': Switch to the default mode where an exception will only
> + insert the address of the memory error into the poison and
> + badblocks lists.
> + '1': Enable a full scrub to happen if an exception for a memory
> + error is received.
> +
> +
> +What: /sys/bus/nd/devices/ndbusX/nfit/dsm_mask
> +Date: Jun, 2017
> +KernelVersion: v4.12
> +Contact: linux-nvdimm@...ts.01.org
> +Description:
> + (RO) The bitmask indicates the supported bus specific control
> + functions.
I'd add:
"See the section named 'NVDIMM Root Device _DSMs' in the ACPI specification."
So, this looks great and is something I've had on my backlog for a
while. That said this is a bit incomplete. These attributes are
relative to the the "nd" bus which is the libnvdimm sub-system sysfs
interface. This document describes that sysfs layout [3]. Ideally that
content would be converted into Documentation/ABI format and merged
with what you have done here into an overall
Documentation/ABI/testing/sysfs-bus-nvdimm file.
I realize that's quite a bit more work, so I'm fine if we start with
the nfit attributes and save that follow on work for a separate patch
in the future.
[3]: https://git.kernel.org/pub/scm/linux/kernel/git/nvdimm/nvdimm.git/tree/Documentation/nvdimm/nvdimm.txt?h=libnvdimm-for-next
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