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What does improved JFFS2 compression mean?It means patches for JFFS2. It contains a rewritten compression framework. New features:
About advanced compressor configurationCompressor configuration is a regular expression like string to specify the mode for JFFS2 how to compress blocks:
How does it work?At JFFS2 there is a compr field in the struct jffs2_raw_inode to identify the compression method used in that node. In most cases it is JFFS2_COMPR_ZLIB which means ZLIB. Using this new method the compression/encoding method is stored not in that compr field (that will be JFFS2_COMPR_ENGINE) but in the begining of the compressed/encoded data. It allows to use not only one algorithm for one block. At decompressing/deconding there will be a loop which will terminated if the begining of the result is 0 and not a valid algorithm name. Downloads
StatusMissing but planned features in the very near future:
How can I use it?You should use the latest JFFS2 snaphot from MTD CVS. Apply the advanced compression patch on it. There will be two versions of mkfs.jffs2: an old one and a new one. The old one works as before. If you whould like to use new mkfs.jffs2 which uses the kernel's CryptoAPI, you should patch your kernel with CryptoDev extension patch, which will provide user space access for the kernel's crypto (and compression) argorithm using the following device file: crw-rw-rw- 1 root root 10, 63 Nov 9 15:28 /dev/crypto Old stuffsSee BBC. |