[SRU] [F/Unstable] [PATCH 0/1] Add sysfs attribute to show remapped NVMe

[Kai-Heng Feng]

BugLink: https://bugs.launchpad.net/bugs/1863621

[Impact]
Intel Rapid Storage Technology hides NVMe behind AHCI controller, to
provide firmware base "fusion drive", like combining with Intel Optane.

There's a driver to support this but upstream doesn't like it for
reasons like NVMe quirks can't be applied when NVMe are behind AHCI
controller.

So we need to devise a mechanism to ask users to change BIOS storage
settings. This patch only provides a new attribute to let userspace like
distro installer know NVMe is remapped behind AHCI.

[Fix]
Add a new attribute to show that how many NVMes are remapped.

[Test]
After applying the patch, there's a new "remapped_nvme" under the AHCI PCI
device sysfs.

If there's no remapped NVMe:
$ cat remapped_nvme
0

If there are two remapped NVMes:
$ cat remapped_nvme
2

[Regression Potential]
Low. It adds a new read only sysfs attribute, no actual functional
change to the AHCI driver.

Kai-Heng Feng (1):
  ata: ahci: Add sysfs attribute to show remapped NVMe device count

 drivers/ata/ahci.c | 28 ++++++++++++++++++++++++----
 drivers/ata/ahci.h |  1 +
 2 files changed, 25 insertions(+), 4 deletions(-)

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2.17.1