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    SubjectRe: [PATCH v2 20/20] libnd, nd_acpi, nd_blk: driver for BLK-mode access persistent memory
    On Tue, Apr 28, 2015 at 11:26 AM, Dan Williams <dan.j.williams@intel.com> wrote:
    > From: Ross Zwisler <ross.zwisler@linux.intel.com>
    >
    > The libnd implementation handles allocating dimm address space (DPA)
    > between PMEM and BLK mode interfaces. After DPA has been allocated from
    > a BLK-region to a BLK-namespace the nd_blk driver attaches to handle I/O
    > as a struct bio based block device. Unlike PMEM, BLK is required to
    > handle platform specific details like mmio register formats and memory
    > controller interleave. For this reason the libnd generic nd_blk driver
    > calls back into the bus provider to carry out the I/O.
    >
    > This initial implementation handles the BLK interface defined by the
    > ACPI 6 NFIT [1] and the NVDIMM DSM Interface Example [2] composed from
    > DCR (dimm control region), BDW (block data window), IDT (interleave
    > descriptor) NFIT structures and the hardware register format.
    > [1]: http://www.uefi.org/sites/default/files/resources/ACPI_6.0.pdf
    > [2]: http://pmem.io/documents/NVDIMM_DSM_Interface_Example.pdf
    >
    > Cc: Andy Lutomirski <luto@amacapital.net>
    > Cc: Boaz Harrosh <boaz@plexistor.com>
    > Cc: H. Peter Anvin <hpa@zytor.com>
    > Cc: Jens Axboe <axboe@fb.com>
    > Cc: Ingo Molnar <mingo@kernel.org>
    > Cc: Christoph Hellwig <hch@lst.de>
    > Signed-off-by: Ross Zwisler <ross.zwisler@linux.intel.com>
    > Signed-off-by: Dan Williams <dan.j.williams@intel.com>
    > ---
    > drivers/block/nd/Kconfig | 12 +
    > drivers/block/nd/Makefile | 3
    > drivers/block/nd/acpi.c | 422 +++++++++++++++++++++++++++++++++++--
    > drivers/block/nd/acpi_nfit.h | 47 ++++
    > drivers/block/nd/blk.c | 264 +++++++++++++++++++++++
    > drivers/block/nd/libnd.h | 11 +
    > drivers/block/nd/namespace_devs.c | 47 ++++
    > drivers/block/nd/nd-private.h | 3
    > drivers/block/nd/nd.h | 16 +
    > drivers/block/nd/region.c | 8 +
    > drivers/block/nd/region_devs.c | 65 +++++-
    > drivers/block/nd/test/nfit.c | 29 +++
    > drivers/block/nd/test/nfit_test.h | 2
    > 13 files changed, 891 insertions(+), 38 deletions(-)
    > create mode 100644 drivers/block/nd/blk.c
    >
    > diff --git a/drivers/block/nd/Kconfig b/drivers/block/nd/Kconfig
    > index 612bf2b14283..bac4290129fc 100644
    > --- a/drivers/block/nd/Kconfig
    > +++ b/drivers/block/nd/Kconfig
    > @@ -95,6 +95,18 @@ config BLK_DEV_PMEM
    >
    > Say Y if you want to use a NVDIMM described by ACPI, E820, etc...
    >
    > +config ND_BLK
    > + tristate "BLK: Block data window (aperture) device support"
    > + depends on LIBND
    > + default ND_ACPI
    > + help
    > + This driver performs I/O using a set of mmio windows on a
    > + dimm. The set of apertures will all access the one DIMM.
    > + Multiple windows allow multiple threads to have a different
    > + portions of the dimm open at one time.
    > +
    > + Say Y if you want to use a NVDIMM with BLK-mode capability
    > +

    This describes how it works, not what it is. How about:

    This driver exposes NVDIMM BLK regions as block devices. BLK regions
    are regions of NVDIMM storage that are sector-addressable, not
    byte-addressible, and do not support DAX.

    Say Y if you want to...

    --Andy


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