Flash filesystem for SH4 7751 Big Sur eval board
- This driver is available only in the
Board Support Packages that need it.
- You must be root to start this driver.
[-a] [-b priority]
[-E] [-f verifylevel] [-i arrayindex[,partindex]]
[-l] [-m mountover]
[-p backgroundpercent[,superlimit]] [-r]
[-t threads] [-u update] [-V] [-v]
SH4 7751 Big Sur Application Development System board
- Don't automount filesystem partitions present on the media.
See also the -R option.
- -b priority
- Enable background reclaim at the specified priority.
By default, background reclamation is disabled.
- Do not daemonize. Exit on EBADFSYS with partition num + 1 of corrupt
- -f verifylevel
- Enable flash verify. (default=0, 0=none, write=1, erase=2, all=3)
- -i arrayindex[,partindex]
- Starting socket index and first partition index;
0 >= index >=15. The default is 0,0.
Use this to give multiple drivers unique IDs.
The -i option is just a suggestion for the resource
database manager; the selected indexes can be larger.
- List the available flash databases and exit.
- -m mountover
- Override the mountpoints assigned to a file system that are formatted with an empty (i.e. flashctl -p/dev/fs0p0 -f -n "") mountpoint.
argument can include two
%X format specifiers (like those for printf())
that are replaced by the socket index and the partition index.
|| The -m option doesn't override a mountpoint specified with
- -p backgroundpercent[,superlimit]
- Set the background-reclaim percentage trigger (stale space over free
space) and, optionally, the superseded extent limit before reclaim.
The default is 100,16.
- Mount the automount filesystem as read-only. It doesn't affect raw
partition mounts. The -R option has an effect only at startup and
initialization. Any subsequent mounting (with either flashctl or
ignores the -R option. If you use -a option, the
-R option is ignored.
- Specify this option always. Enable fault recovery for
dirty extents, dangling extents, and partial reclaims. If you
don't specify -r, recovery isn't performed, which, when power
faults are likely, can waste space on the media or make the media
read-only. You should always specify the -r option unless you're
trying to debug a flash corruption issue or you don't have the
time to repair a damage.
- -s base[,wsize[,aoffset[,asize[,usize[,bwidth[,ileave]]]]]]
- Set socket options, normally the base physical address, window size,
array offset, array size, unit size, bus width, and interleave. The format is left flexible
for socket services with customized drivers.
The arguments are:
- Physical base address of the flash part. This value is board-specific.
- Size of the physically contiguous flash part.
- For SRAM, the offset from the base address to the start of the flash
- For SRAM, the size of the flash array. The default is equal to
- The size of a physical erase sector. For SRAM, this number can be any
power of two. 64K should be the minimum, for performance reasons.
- The total width of the data bus, as seen from the microprocessor's
perspective. This is the width of one flash chip multiplied by the
The value is specified as a power of 2 (1,2,4,8).
- The number of flash chips arranged on the data bus.
Two 16-bit wide chips used as the upper and lower halves of a 32-bit
databus give an interleave of 2. This number is specified as a power
of 2 (1,2,4).
You can specify the base physical address, sizes, and offset
in octal (0777), hexadecimal (0x1ff), or
The sizes must be a power of two, and you can specify them with any of
the following suffixes:
- (nothing) -- bytes
- k -- kilobytes
- m -- megabytes
- -t threads
- Number of threads;
1 >= threads >= 4
(default is 2). Extra threads increase performance when
background reclaim is enabled (with the -b option) and
when multiple chips and/or spare blocks are available.
- -u update
- Update level for timestamps; 0 for never update,
1 to update files only, and 2 to update files
and directories. The default update is 0.
- Display filesystem and MTD version information.
- Display verbose information.
- -w buffersize
- Write (append) buffer size in bytes. The default
buffersize is 512. Using a larger write-buffer
prevents the creation of very small extents, reducing overhead.
If buffersize is 0, appending is disabled.
The devf-bigsur manager provides Flash filesystem
support for SH4 7751 Big Sur eval board using the
following default filenames (the ID, n, appended to
be changed via the -i option):
- Default mountpoint for socket n.
- Raw access for socket n, partition 0.
- Flash filesystem mountpoint for socket n, partition 0 with
||You should always specify the -r option unless you're trying to
debug a flash corruption issue or you don't have the time to repair a damage.
See the background information for this:
- If an erase was happening when the power is cut off,
it results in a number of dangling extents at the next
power on. These extents continue to occupy space forever, until they
are deleted. Using the -r option will cause them to be deleted.
If you start the the driver with -vv, it prints dangle
every dangling extent found.
- If the
filesystem detects an error, and the -r isn't specified, the
driver marks the partition read-only, so that more damage isn't done.
The second case is when a reclaim was interrupted by a power-loss. In this
case the spare block may be unusable and the driver prints
partial to the console. The partition is still read-write, but
turned off, which means overwriting of files will eventually fill up the
filesystem with stale data.
You can specify the mountpoint above with the
mount attribute of the
command, and override it with the
-n option to
By default, it's /fsnp0.
||If you erase a raw partition or the raw array (socket),
you might erase any boot monitor,
BIOS, or other data installed by the manufacturer.
Check the documentation for the board.|
The driver probes the hardware to determine its block size.
If you need to know the block size, you can:
- Look in the documentation for the hardware.
- Start the driver in verbose mode by specifying the -v option.
In the output, U: indicates the number of units (i.e. blocks),
and S: indicates the block size.
Both numbers are in hexadecimal.
- Start the driver, and then run
specifying the -i option.
Start devf-bigsur and automatically mount the Flash filesystem
partitions, with an initial fault recovery process, most POSIX semantics
enabled and background reclaim at priority 5:
devf-bigsur -r -u2 -b5 &
Create a 32MB flash partition, with a 64KB unit (sector) size:
devf-bigsur -s0,32m,,,64k -v -r
Create a 128MB flash partition, with large block sizes (to
devf-bigsur -s0,128m,,,512k -v -r
Create a 4MB partition:
devf-bigsur -s0,4m,,,64k -v -r
Create a 16MB flash partition, from a given physical address, with a 128KB
unit size, and a 16-bit wide data bus:
devf-generic -s0xa4000000,16m,,,128k,2 -v -r
Create a 16MB flash partition, from a given physical address, with a 256KB
unit size, and a 32-bit-wide data bus, with an interleave of two:
devf-generic -s0,16m,,,256k,4,2 -v -r
Although the Flash filesystem supports most POSIX semantics, some
functionality isn't implemented in order to keep the driver simple and
efficient. The unsupported POSIX semantics include:
- Hard links, and everything related to hard links (the
. and .. directories don't exist,
struct stat's nlink member is hard-coded,
of directories returns ENOTSUP).
- Access times aren't updated on the media; they're set to
the modification time.
QNX Neutrino flash filesystem version 3 no longer
provides built-in decompression.
The flash filesystem's decompression functionality has moved into the
resource manager. You should now use the deflate utility to compress files.
Performance might be slow when multiple writers are writing randomly
to a shared file or to a shared directory (e.g. using unlink or
In these cases,
the offset pointers have to be rewound for every access.
There's no performance penalty when appending to a file, or when
creating files with open(O_CREAT),
mkdir, mknod, or link.
in the Working With Filesystems chapter of the User's Guide