Getting dual tuner KWorld U399 USB DVB-T working on linux 2.6.37

I recently upgraded the kernel version on my MythTV. One side affect of this was that the second tuner for my DVB-T USB stick (an af9015 based KWorld U399) no longer existed in /dev/dvb. In previous versions of the af9015 module it was just a case of explicitly enabling it with a module parameter of dual_mode=1 and possibly suffering some reception issues when both tuners are enabled.

To get the second tuner working it's necessary to use the very latest firmware for the device. So download the firmware file from here and place it in /lib/firmware. From a quick look at the source code for af9015 it looks like the driver now checks a value in the EEPROM to see if dual mode is safe or not. I assume the clever developer for the af9015 driver has worked out that this is what determines if there will be reception issues with both tuners enabled and that the 5.1.0.0 firmware updates this EEPROM in a suitable way.

You'll need to unplug your USB stick and replug it in to get it to use the new firmware, but you should then get two DVB tuners.