V4L2 and norm switching — Video for Linux

  I'm (finally) doing V4L2 support in tvtime.  For testing I've been
using bttv-0.9.10 and bttv9-20030606 with v4l2-20030606.

  I have been having some difficulties with norm switching.  In tvtime,
we support norm switching for areas which receive both PAL and SECAM
channels: we don't change the capture size, just change the norm.  For
my testing, since I'm in an NTSC area, I usually switch between NTSC and
NTSC-JP.

  I'm curious about how norm switching and capturing are supposed to
interact.  Do I need to stop streaming before changing the norm?  For
some norms, parameters such as the max frame size may change.  When
should I negotiate the format?

  I've been having some problems in my testing, and found a reproducable
panic with bttv9-20030606.

  I see this alot:

  bttv0: skipped frame. no signal? high irq latency?

  And here is my panic:

kernel BUG at btcx-risc.c:67!
invalid operand: 0000
CPU:    0
EIP:    0010:[<e08de0ae>]    Not tainted
EFLAGS: 00010286
eax: 00000000   ebx: 000009e8   ecx: 00000000   edx: dc8c4000
esi: d599a5f0   edi: dc8c49e8   ebp: 00000500   esp: dca7bba8
ds: 0018   es: 0018   ss: 0018
Process tvtime (pid: 27180, stackpage=dca7b000)
Stack: 00000500 00000000 d599a560 1c8c4000 e08eb0e6 c1592000 d599a5f0 000009e8
       00000500 0004b000 d599a560 e08ed1bc 00000016 e08ec172 e08f5dc0 d599a5f0
       d1bd4000 00000000 00000500 00000500 000000f0 000001e0 d599a560 00000280
Call Trace:    [<e08eb0e6>] [<e08ed1bc>] [<e08ec172>] [<e08f5dc0>] [<e08ed1bc>]
  [<e08ecfe8>] [<e08e4fe2>] [<e08f5dc0>] [<e08e509e>] [<e08f5dc0>] [<e08ed1bc>]
  [<e08e0c7d>] [<e08e712f>] [<e08f5dc0>] [<c0129bb6>] [<c0120e06>] [<c013b2ee>]
  [<e083e0dd>] [<e083f6c0>] [<c0107e7d>] [<c010a278>] [<c0108001>] [<c010a1c8>]
  [<c0209134>] [<c01114d0>] [<c011af3c>] [<c0187d55>] [<c0117dca>] [<c0187d55>]
  [<c0129b0e>] [<c0129dc0>] [<c018a07b>] [<c0186a53>] [<c018a07b>] [<e08a9441>]
  [<c018465a>] [<e08e7428>] [<e08e60ec>] [<c013b5d7>] [<c0106bc7>]

Code: 0f 0b 43 00 c0 e4 8d e0 89 56 04 8b 44 24 0c 89 46 0c 89 1e
 bttv0: skipped frame. no signal? high irq latency?
bttv0: skipped frame. no signal? high irq latency?


  Thanks,
  -Billy