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tridge has done it again, offering a patch to Linux's VFAT filesystem that retains support for long names, while carefully avoiding ever having both a long and a short name for the same file.

And here is the FAQ. Note particularly what can and can't be safely discussed regarding patents on LKML.

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Q3. Why should we apply a patch to avoid a patent that might be invalid?

A3. It takes a lot of time in the courts (and thus, a lot of money)
to legally prove that a patent is invalid, and in the meantime
the patent remains at least a nuisance and in practice still
dangerous. Any damage done during this time period, to both
persons and organizations, might well be permanent -- it might
never be possible to repair that damage, even if the patent
should eventually be invalidated. On the other hand, a patch
that avoids both the patent and regressions in function and
performance can greatly reduce the danger of such damage.

One of the specific dangers that needs to be addressed is
illustrated by the ITC action that Microsoft took against TomTom:

»www.itcblog.com/20090227/microso···devices/

That ITC action asked for TomTom's products to be seized at US
borders, and might have effectively shutdown TomTom as a going
concern in the US. If Microsoft did the same thing to another
Linux vendor then even though the vendor might eventually win
they could still be severely damaged just by having their market
disrupted or frightened.

The way to avoid this is to ensure that the Linux kernel is so
obviously non-infringing that the case does not even go to trial.
That means you have to have an extremely clear explanation of how
the patent does not apply to your code. The aim of the patches we
have posted is to ensure that we would meet that standard.

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Linux developers want to circumvent VFATs patent problem

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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