hello, I am having trouble getting 3+ recorders drivers loaded and working properly, and I suspect it has to do with the number of recorders and memory limitations and/or lack of kernel parameters to accomodate the greater number of cards.  I have 3 Hauppauge_WinTV-HVR-1250 PCIe cards of which only 2 are working.  I have 1 pcHDTV_HD5500 PCI card which is working (so a total of 3 recorders are working).
I am trying to get a KWorld_UB435-Q USB working on the same machine and it gives me the following error:
stack trace and then: "unable to allocate 196608 bytes for transfer buffer 0"
"em2874 #0: em28xx_dvb: failed to pre-allocate USB transfer buffers for DVB."
are you installing that on some pentium with 64meg ram?
dongs:  no, but a very "modest" machine:   Dual Core E5300 2.6Ghz, 2 GB RAM
more than enough then
right, but I think tweaking driver parameters is required (if that will even work) since the drivers for individual cards were probably not originally written for handling 3+ cards of different types on the same machine..
for example, i remember facing an issue with multiple Hauppauge_WinTV-HVR-1600 PCI on the same machine:  https://www.mythtv.org/wiki/Common_Problem:_vmalloc_too_small
but that was a few years ago
you better look at em28xx drirver and see what its trying to do
and why its failing
soresis open.
the em28xx seems to work when using it exclusively or with 1 other recorder.  it fails when using it on a machine that already has 4 internal recorder cards (3 of which are working).
`modprobe em28xx`  shows some parameters but i'm not sure if tweaking any will fix the problem.  also, is it possible to tweak those driver parmaters without rebooting? 
if so ,how?
sorry, i meant:  `modinfo em28xx`