Comment 11 for bug 864051

Looking at the initial commit for TRIM in the kernel I can see that it's calling ata_id_has_trim() and passing in the disks ID. This looks like it filters disks that don't support TRIM.

You can see the commit for trim in the 2.6.33 kernel here:

http://git.kernel.org/?p=linux/kernel/git/torvalds/linux-2.6.git;a=commitdiff;h=18f0f97850059303ed73b1f02084f55ca330a80c

If you want to investigate the ata_id_has_trim function more closely you can find it in include/linux/ata.h.