Hi, I've compiled kernel 2.6.26 myself, I did install the modules, 
and the modules load successfully

here is from my dmesg:

usbcore: registered new interface driver r5u870
scsi 2:0:0:0: Direct-Access     Sony     USB   HS-CARD    4.52 PQ: 0 
ANSI: 0
usb-storage: device scan complete
Modules linked in: snd_seq_oss snd_seq_midi_event snd_seq 
snd_seq_device snd_pcm_oss snd_mixer_oss snd_intel8x0m snd_intel8x0 
snd_ac97_codec ac97_bus snd_hda_intel snd_pcm r5u870 snd_timer 
snd_page_alloc usbcam videobuf_dma_sg snd_hwdep videobuf_core 
ipw3945 snd
 [<f88d0b9b>] usbcam_v4l_open+0x7b/0x210 [usbcam]

When I try to run v4l-info, I got nothing. the command do nothing 
and I can not get back to the shell by  CTRL-C or CTRZ-Z.

I find the following in the end of my dmesg:

------------[ cut here ]------------
kernel BUG at drivers/media/video/videobuf-core.c:137!
invalid opcode: 0000 [#1] SMP
Modules linked in: snd_seq_oss snd_seq_midi_event snd_seq 
snd_seq_device snd_pcm_oss snd_mixer_oss snd_intel8x0m snd_intel8x0 
snd_ac97_codec ac97_bus snd_hda_intel snd_pcm r5u870 snd_timer 
snd_page_alloc usbcam videobuf_dma_sg snd_hwdep videobuf_core 
ipw3945 snd

Pid: 8779, comm: v4l-info Not tainted (2.6.26-gentoo #18)
EIP: 0060:[<f885f3e8>] EFLAGS: 00010246 CPU: 0
EIP is at videobuf_queue_core_init+0xb8/0xd0 [videobuf_core]
EAX: f88d0fa0 EBX: f75ae2c8 ECX: 00000000 EDX: 00000000
ESI: f88d1b50 EDI: f88d19e0 EBP: f88757e0 ESP: f2025e00
 DS: 007b ES: 007b FS: 00d8 GS: 0033 SS: 0068
Process v4l-info (pid: 8779, ti=f2024000 task=f044bc00 
task.ti=f2024000)
Stack: 00000000 00000000 f7a52b14 00000000 00000078 f75ae2c0 
f7257388 f8873089
       00000000 00000001 00000004 00000078 f75ae2c0 f88757e0 
f7257000 f88d0b9b
       00000000 00000001 00000004 00000078 f75ae2c0 f30731c0 
00000000 c01795fe
Call Trace:
 [<f8873089>] videobuf_queue_sg_init+0x39/0x40 [videobuf_dma_sg]
 [<f88d0b9b>] usbcam_v4l_open+0x7b/0x210 [usbcam]
 [<c01795fe>] cdev_get+0x2e/0x50
 [<c03879dc>] video_open+0x9c/0x140
 [<c0179510>] exact_match+0x0/0x10
 [<c0179be0>] chrdev_open+0xa0/0x1a0
 [<c0179b40>] chrdev_open+0x0/0x1a0
 [<c0175367>] __dentry_open+0xb7/0x240
 [<c0175535>] nameidata_to_filp+0x45/0x60
 [<c01819f3>] do_filp_open+0x173/0x710
 [<c01637bf>] handle_mm_fault+0x10f/0x5b0
 [<c0177eaf>] __fput+0x11f/0x190
 [<c017508f>] get_unused_fd_flags+0x4f/0xc0
 [<c017f8d3>] getname+0xb3/0xe0
 [<c017514c>] do_sys_open+0x4c/0xe0
 [<c017525c>] sys_open+0x2c/0x40
 [<c0103ed9>] sysenter_past_esp+0x6a/0x91
 [<c05a0000>] get_cpu_vendor+0x60/0xb0
 =======================
Code: ff fc 8d c7 8d 43 18 e8 67 d3 8d c7 8d 83 c4 00 00 00 89 40 04 
89 83 c4 00 00 00 83 c4 0c 5b 5e 5f 5d c3 0f 0b eb fe 0f 0b eb fe 
<0f> 0b eb fe 8d 74 26 00 0f 0b eb fe 0f 0b eb fe 0f 0b eb fe 8d
EIP: [<f885f3e8>] videobuf_queue_core_init+0xb8/0xd0 [videobuf_core] 
SS:ESP 0068:f2025e00
---[ end trace c72cd1bdb3731f6b ]---

I've attached my .config too.

Any clue?