How to control debugging in yaffs
YAFFS provides a debugging mechanism which can be controlled at runtime if you have access to /proc, normally via a shell. If you need to trace things before you get to a shell, then you can set default trace options at compile time.
Available Trace Flags
| name | C #define | bitmask value |
|---|---|---|
| error | YAFFS_TRACE_ERROR | 0x00000001 |
| os | YAFFS_TRACE_OS | 0x00000002 |
| allocate | YAFFS_TRACE_ALLOCATE | 0x00000004 |
| scan | YAFFS_TRACE_SCAN | 0x00000008 |
| bad_blocks | YAFFS_TRACE_BAD_BLOCKS | 0x00000010 |
| erase | YAFFS_TRACE_ERASE | 0x00000020 |
| gc | YAFFS_TRACE_GC | 0x00000040 |
| write | YAFFS_TRACE_WRITE | 0x00000080 |
| tracing | YAFFS_TRACE_TRACING | 0x00000100 |
| deletion | YAFFS_TRACE_DELETION | 0x00000200 |
| buffers | YAFFS_TRACE_BUFFERS | 0x00000400 |
| nandaccess | YAFFS_TRACE_NANDACCESS | 0x00000800 |
| gc_detail | YAFFS_TRACE_GC_DETAIL | 0x00001000 |
| scan_debug | YAFFS_TRACE_SCAN_DEBUG | 0x00002000 |
| mtd | YAFFS_TRACE_MTD | 0x00004000 |
| always | YAFFS_TRACE_ALWAYS | 0x40000000 |
| bug | YAFFS_TRACE_BUG | 0x80000000 |
Flag meanings
The flags cover possible debugging messages from various aspects of the filesystem - initial scanning, mtd interface, writing, nand access, garbage collection, OS interaction etc. Turning on everything results an awful lot of trace info, so it is usually best to just enable a few relevant flags.
Setting flags at runtime
The flags can be set or cleared by echoing the name of the flag into /proc/yaffs with a '+' or '-':
echo +os-write > /proc/yaffs
It can be set to to all or none using '=', and then flags can be added or removed:
echo =none+os+write > /proc/yaffs
And you can use numerical values, if you are so inclined (using standard C format):
echo 0xf00001 > /proc/yaffs
So
echo all > /proc/yaffs
will turn all tracing on
Note that you only see the output showing you the current trace state if the 'always' (YAFFS_TRACE_ALWAYS) flag is set, so to see what you are doing do this:
echo +always > /proc/yaffs
Setting flags at compile time
Flags can be set in the code at compile-time by setting yaffs_traceMask in yaffs_fs.c (add new flags to always and bad_blocks which are set by default)