Add qemu 2.4.0

[kvmfornfv.git] / qemu / roms / u-boot / doc / README.JFFS2

diff --git a/qemu/roms/u-boot/doc/README.JFFS2 b/qemu/roms/u-boot/doc/README.JFFS2
new file mode 100644 (file)
index 0000000..f0e9bc1
--- /dev/null
+++ b/qemu/roms/u-boot/doc/README.JFFS2
@@ -0,0 +1,74 @@
+JFFS2 options and usage.
+-----------------------
+
+JFFS2 in U-Boot is a read only implementation of the file system in
+Linux with the same name. To use JFFS2 define CONFIG_CMD_JFFS2.
+
+The module adds three new commands.
+fsload  - load binary file from a file system image
+fsinfo  - print information about file systems
+ls      - list files in a directory
+chpart  - change active partition
+
+If you boot from a partition which is mounted writable, and you
+update your boot environment by replacing single files on that
+partition, you should also define CONFIG_SYS_JFFS2_SORT_FRAGMENTS. Scanning
+the JFFS2 filesystem takes *much* longer with this feature, though.
+Sorting is done while inserting into the fragment list, which is
+more or less a bubble sort. That algorithm is known to be O(n^2),
+thus you should really consider if you can avoid it!
+
+
+There is two ways for JFFS2 to find the disk. The default way uses
+the flash_info structure to find the start of a JFFS2 disk (called
+partition in the code) and you can change where the partition is with
+two defines.
+
+CONFIG_SYS_JFFS2_FIRST_BANK
+       defined the first flash bank to use
+
+CONFIG_SYS_JFFS2_FIRST_SECTOR
+       defines the first sector to use
+
+
+The second way is to define CONFIG_SYS_JFFS_CUSTOM_PART and implement the
+jffs2_part_info(int part_num) function in your board specific files.
+In this mode CONFIG_SYS_JFFS2_FIRST_BANK and CONFIG_SYS_JFFS2_FIRST_SECTOR is not
+used.
+
+The input is a partition number starting with 0.
+Return a pointer to struct part_info or NULL for error;
+
+Ex jffs2_part_info() for one partition.
+---
+#if defined CONFIG_SYS_JFFS_CUSTOM_PART
+#include <jffs2/jffs2.h>
+
+static struct part_info part;
+
+struct part_info*
+jffs2_part_info(int part_num)
+{
+       if(part_num==0){
+               if(part.usr_priv==(void*)1)
+                       return &part;
+
+               memset(&part, 0, sizeof(part));
+               part.offset=(char*)0xFF800000;
+               part.size=1024*1024*8;
+
+               /* Mark the struct as ready */
+               part.usr_priv=(void*)1;
+
+               return &part;
+       }
+       return 0;
+}
+#endif
+---
+
+TODO.
+
+       Remove the assumption that JFFS can dereference a pointer
+       into the disk. The current code do not work with memory holes
+       or hardware with a sliding window (PCMCIA).