[settings] Explicitly separate the concept of a completed fetched setting
The fetch_setting() family of functions may currently modify the
definition of the specified setting (e.g. to add missing type
information). Clean up this interface by requiring callers to provide
an explicit buffer to contain the completed definition of the fetched
setting, if required.
Signed-off-by: Michael Brown <mcb30@ipxe.org>
[settings] Expose memory map via settings mechanism
Allow memory map entries to be read using the syntax
${memmap/<region>.<properties>.<scale>}
where <region> is the index of the memory region, <properties> is a
bitmask where bit 0 represents the start address and bit 1 represents
the length (allowing the end address to be encoded by having both bits
0 and 1 set), and <scale> is the number of bits by which to shift the
result.
This allows for several values of interest to be encoded. For
example:
${memmap/<region>.1.0:hexraw} # 64-bit start address of <region>
${memmap/<region>.2.0:hexraw} # 64-bit length of <region>, in bytes
${memmap/<region>.3.0:hexraw} # 64-bit end address of <region>
${memmap/<region>.2.10:int32} # Length of <region>, in kB
${memmap/<region>.2.20:int32} # Length of <region>, in MB
The numeric encoding is slightly more sophisticated than described
here, allowing a single encoding to cover multiple regions. (See the
source code for details.) The primary use case for this feature is to
provide the total system memory size (in MB) via the "memsize"
predefined setting.
Signed-off-by: Michael Brown <mcb30@ipxe.org>
Michael Brown