03/30/2010 10:27 AM
RE: Scanning for start of file system partition
I'm not sure I understand what you're asking. The HDD filesystems have
a standard MBR which describes each partition, and the NOR and NAND
filesystems (devf and ETFS respectively) have to scan a given range in
order to detect the presence of the filesystem on the flash (since, for
wear levelling and power safety, structures are allowed to migrate
within the partition).
In the case of traditional raw flash (NOR or NAND), there is no format
for the raw partition, hence why it is called "raw". This is simply a
physical range of flash that the filesystem drivers do not try to
interpret, and only provides basic "passthrough" access for. In the
ETFS case, the size of the raw partition is given on the command-line,
so that the driver can skip that range when loading the filesystem. For
the devf drivers, the driver scans the entire device to detect any
formatted filesystems. Raw partitions are simply ranges of blocks which
do not belong to formatted filesystems.
If I misunderstand, please clarify. What is the specific problem you
are trying to solve?
> -----Original Message-----
> From: Gordon Molek [mailto:firstname.lastname@example.org]
> Sent: March 30, 2010 10:04 AM
> To: general-bsp
> Subject: Scanning for start of file system partition
> The IPL currently scans the raw flash partition and detects
> IFSes based on a starting block number and an ending block
> number. We would like to know if there is documentation on
> the format of the first block of the file system partition so
> that we could scan for that as part of the IPL scan and not
> have to hard code a raw partition size.
> The IPL could then pass the file system partition block
> number (or size of the raw partition) to the IFS it selects
> to run as part of the boot info structure. That way, neither
> the IPL nor the IFSes need to hardcode the raw partition size
> (and don't have to be kept in sync).
> QNX BSPs