mmc: Add read-only directory to support mboxd

The mboxd implementation assumes that there is a read-only and
read-write directory. During a write request, mboxd copies the
contents o

mmc: Add read-only directory to support mboxd

The mboxd implementation assumes that there is a read-only and
read-write directory. During a write request, mboxd copies the
contents of the read-only to the read-write directory. To continue
to support mboxd, mount a read-only directory of the hostfw image
for mboxd to use. Otherwise the write command fails (can't copy
the file to itself) and mboxd exits.

Tested: Verified mboxd didn't fail and system powered on.

Change-Id: Idcb8ff0c5eee0179d5d70e60e5e01c7d0f76b880
Signed-off-by: Adriana Kobylak <anoo@us.ibm.com>

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mmc: Setup hostfw directories

The BMC updater will take care of writing the new hostfw image
to flash since it's delivered in the single tarball file, but
when the BMC starts up, nee

mmc: Setup hostfw directories

The BMC updater will take care of writing the new hostfw image
to flash since it's delivered in the single tarball file, but
when the BMC starts up, need to setup the directories so that
the contents of the host FW are visible to consumers like pldm.

The first service is to setup the patch directory. This is
similar to UBI. The path that mboxd expects (pnor) will point to
a directory in the hostfw partition. Then create a similar
symlink (hostfw) for pldm to use. Eventually pldm will replace
mboxd.

The second service is an init setup. We need to make the 2 hostfw
versions visible. The secondary (non-running) will just be a
read-only mount of the non-running image. The primary (running)
version needs to be read-write. The mboxd code currently
handles 3 directories: ro, rw, prsv. This was deemed too complex
for pldm to replicate, so it was decided to have a single rw
directory, then pldm would determine if it allowed a write or not.
To handle the preserved files (that are not updated on an update),
need to copy them off to a tmp space, then set up the primary
directory with the contents of the running image, then restore the
preserved files. Currently only the PNOR contents are preserved,
at a later point the pldm files will be preserved and a different
list like the pnor.toc file will be added.

Finally, like the vpnor util does, if the version has changed on,
remove the patch files. Just that we need to do this when the init
service starts because the symlinks will not change at runtime
(the host fw version is tied to the bmc version).

Change-Id: I32b456bd363671404f573cb941a0f2f374a3eab2
Signed-off-by: Adriana Kobylak <anoo@us.ibm.com>

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