Aligning os_args Values and the Mass Storage Layout
When flashing a device, the flashing script uses the configuration file to determine how
to flash individual partitions. os_args
attributes provide a kernel
command line that specifies file system and partition attributes. Of particular interest
are the settings for Memory Technology Device (MTD) devices, which use QSPI flash.
If you change your flash partition layout, you must also modify the attributes in
os_args
to be consistent with the mass storage layout. For example,
if you move the data partition, you must also update the offsets or indices in the
os_args value. Such modifications are required to ensure non-overlapping partitions.
By default, the OS kernel has no knowledge of the mass storage layout created when
flashing (i.e., QSPI partition offset and size, and file system type). At runtime, the
kernel cannot determine all layout settings. In particular, the os_args
attribute may need to specify the Linux kernel settings described in the following table.
os_args Settings | Description |
---|---|
rootfstype=ubifs | Required if the root file system is UBIFS. Unlike the ext2/ext3/ext4 file systems, the kernel cannot at runtime detect UBIFS. |
root=ubi<n>_<m> Where: <n> is the sequential number of the UBI device (usually 0) <m> is the "id" attribute on the partition. |
Required if the root device is a UBI volume. The alternative form of this value is
|
ubi.mtd=<x> Where |
Required to attach the UBI to the MTD partition at boot, for example, if the root device is a UBI volume. |
Where: • • • |
Required to export NOR partitions as mtdN and mtdblockN devices. For
example, use this key-value pair to export the partition at offset
|
For information on all supported kernel command parameters, see the following file.
kernel/Documentation/kernel-parameters.txt