For ATA-8 devices, per "TRIM – DRAT / RZAT clarifications for ATA8-ACS2" (http://www.t13.org/Documents/UploadedDocuments/docs2010/e09158r2-Trim_Clarifications.pdf) there is TRIM specific feature information in the Identify Block. See "Table X – TRIM related interactions" on page 5.
For people working with disk drives as a potential source of evidence in a trial it is useful to know what support for Trim a drive advertises. Thus it would be great if hdparm -I would decode the bits described in that table. (Yes I know we can get use hdparm to extract the entire Identify Block and then decode those bits ourselves, but it would be nicer if -I did it automatically.)