V4L/DVB (7366): Support for a 16-channel bt878 card

I have what looks like a Geovision GV-600 (or 650) card. It has a large
chip in the middle labeled

CONEXANT
FUSION 878A
25878-13
E345881.1
0312 TAIWAN

It has an audio connector coming out from a chip labeled

ATMEL
0242
AT89C2051-24PI

It is identified as follows on my Debian GNU/Linux Etch (kernel 2.6.18)

...
01:0a.0 Multimedia video controller: Brooktree Corporation Bt878 Video Capture (rev 11)
01:0a.1 Multimedia controller: Brooktree Corporation Bt878 Audio Capture (rev 11)
...
01:0a.0 0400: 109e:036e (rev 11)
        Subsystem: 008a:763c
        Flags: bus master, medium devsel, latency 64, IRQ 58
        Memory at dfffe000 (32-bit, prefetchable) [size=4K]
        Capabilities: [44] Vital Product Data
        Capabilities: [4c] Power Management version 2

01:0a.1 0480: 109e:0878 (rev 11)
        Subsystem: 008a:763c
        Flags: bus master, medium devsel, latency 64, IRQ 58
        Memory at dffff000 (32-bit, prefetchable) [size=4K]
        Capabilities: [44] Vital Product Data
        Capabilities: [4c] Power Management version 2

It was being detected as a GENERIC UNKNOWN CARD both by the 2.6.18
kernel and the latest v4l-dvb drivers, but it did not work at all. The
card has sixteen (16) BNC video inputs, four of them on the board itself
and twelve on three daughter-cards. It has a single bt878 chip, no tuner
and what looks like and audio input. After doing some research I managed
to get only eight channels working by forcing card=125 and those DID NOT
match channels 0-7 on the card, and no audio.

Based on what was working for card=125, I added the card definition
block, added a specific muxsel routine and got the card working fully
with xawtv, where the sixteen channels show up as Composite0 to
Composite15, matching the channel labels in the card and daughter-cards.
I have made no efforts yet to get audio working, but would appreciate
any pointers.

Signed-off-by: Ernesto Hernández-Novich <emhn@usb.ve>
Signed-off-by: Mauro Carvalho Chehab <mchehab@infradead.org>