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29 June 2009, 14:57

Linux developers want to circumvent VFATs patent problem

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Nearly two months after his first VFAT patch, Andrew Tridgell, Samba developer and IBM employee, has now released a second patch which should make it possible to circumvent the patent issue with the VFAT implementation in Linux.

The original workaround, CONFIG_VFAT_NO_CREATE_WITH_LONGNAMES, which effectively prohibited creation or modification of files with long file names, but allowed the read only use of existing long file named files without problems. The new workaround, CONFIG_VFAT_FS_DUALNAMES, does not limit the functionality of the VFAT implementation. Instead, a boolean variable is used which sets whether a short or a long file name is created, but never creates both. The fields that normally contain the short name are then filled with invalid characters, so the result, in FAT terms, is not a valid short file name.

The reason for the two kernel patches is the now settled case between Microsoft and TomTom which named the long file name patents on FAT as part of the patent violation case. It is hoped that Tridgell's second patch minimises the risk of patent violation. Both FAT patents from Microsoft refer explicitly to the creating or saving of both long and short file names; the patch makes it so the Linux VFAT implementation never simultaneously creates both long and short file names.


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