This patch has been backported for 2.6.16.1 from the following patch,
which is queued for 2.6.17:

V4L/DVB (3495): Kconfig: select VIDEO_CX25840 to build cx25840 a/v 
decoder module
http://www.kernel.org/git/?p=linux/kernel/git/mchehab/v4l-dvb.git;a=commitdiff;h=4f767be057d0173eae7ef116de32a3f4f12888a8