• ref : microdia, sn9c20x-sysfs.c

static DEVICE_ATTR(release, S_IRUGO, show_release, NULL);							/**< Release value */
static DEVICE_ATTR(videostatus, S_IRUGO, show_videostatus, NULL);						/**< Video status */
static DEVICE_ATTR(information, S_IRUGO, show_information, NULL);						/**< Information */
...

$ pwd
/sys/devices/pci0000:00/0000:00:1d.7/usb1/1-4/1-4.1/1-4.1:1.0/video4linux/video0
suapapa@suapapa-desktop:video0$ ls
auto_exposure      brightness  dev     exposure  gamma  index         name   release    subsystem  vflip
auto_whitebalance  contrast    device  fps       hflip  informations  power  sharpness  uevent     videostatus
$ cat videostatus 
Overflow frames    : 0
Incomplete frames  : 0
Dropped frames     : 0