nvdimm/blk: Delete the block-aperture window driver

Block Aperture Window support was an attempt to layer an error model
over PMEM for platforms that did not support machine-check-recovery.
However, it was abandoned before it ever shipped, and only ever existed
in the ACPI specification. Meanwhile Linux has carried a large pile of
dead code for non-shipping infrastructure. For years it has been off to
the side out of the way, but now CXL and recent directions with DAX
support have the potential to collide with this code.

In preparation for adding discontiguous namespace support, a
pre-requisite for the nvdimm subsystem to replace device-mapper for
striping + concatenation use cases, delete BLK aperture support.

On the obscure chance that some hardware vendor shipped support for this
mode, note that the driver will still keep BLK space reserved in the
label area. So an end user in this case would still have the opportunity
to report the regression to get BLK-mode support restored without
risking the data they have on that device.

Reviewed-by: Christoph Hellwig <hch@lst.de>
Link: https://lore.kernel.org/r/164688416668.2879318.16903178375774275120.stgit@dwillia2-desk3.amr.corp.intel.com
Signed-off-by: Dan Williams <dan.j.williams@intel.com>

1 files changed, 4 insertions, 21 deletions

diff --git a/drivers/nvdimm/Kconfig b/drivers/nvdimm/Kconfig
index 347fe7afa583..5a29046e3319 100644
--- a/drivers/nvdimm/Kconfig
+++ b/drivers/nvdimm/Kconfig
@@ -10,12 +10,9 @@ menuconfig LIBNVDIMM
 	  ACPI-6-NFIT defined resources.  On platforms that define an
 	  NFIT, or otherwise can discover NVDIMM resources, a libnvdimm
 	  bus is registered to advertise PMEM (persistent memory)
-	  namespaces (/dev/pmemX) and BLK (sliding mmio window(s))
-	  namespaces (/dev/ndblkX.Y). A PMEM namespace refers to a
+	  namespaces (/dev/pmemX). A PMEM namespace refers to a
 	  memory resource that may span multiple DIMMs and support DAX
-	  (see CONFIG_DAX).  A BLK namespace refers to an NVDIMM control
-	  region which exposes an mmio register set for windowed access
-	  mode to non-volatile memory.
+	  (see CONFIG_DAX).
 
 if LIBNVDIMM
 
@@ -38,19 +35,6 @@ config BLK_DEV_PMEM
 
 	  Say Y if you want to use an NVDIMM
 
-config ND_BLK
-	tristate "BLK: Block data window (aperture) device support"
-	default LIBNVDIMM
-	select ND_BTT if BTT
-	help
-	  Support NVDIMMs, or other devices, that implement a BLK-mode
-	  access capability.  BLK-mode access uses memory-mapped-i/o
-	  apertures to access persistent media.
-
-	  Say Y if your platform firmware emits an ACPI.NFIT table
-	  (CONFIG_ACPI_NFIT), or otherwise exposes BLK-mode
-	  capabilities.
-
 config ND_CLAIM
 	bool
 
@@ -67,9 +51,8 @@ config BTT
 	  applications that rely on sector writes not being torn (a
 	  guarantee that typical disks provide) can continue to do so.
 	  The BTT manifests itself as an alternate personality for an
-	  NVDIMM namespace, i.e. a namespace can be in raw mode (pmemX,
-	  ndblkX.Y, etc...), or 'sectored' mode, (pmemXs, ndblkX.Ys,
-	  etc...).
+	  NVDIMM namespace, i.e. a namespace can be in raw mode pmemX,
+	  or 'sectored' mode.
 
 	  Select Y if unsure