C - how can i reset the USB Bus under linux? -

daily--about 5 10 times--my usb camera disappears system. it's been happening day 1 because manufacturer driver not compatible linux. lsusb , dmesg show correctly @ first, after longer period of time disappears. best solution fix reset usb interface camera back. did few times manually using c source code , worked, when doing in bash loop seems it's failing on , over. idea?

how can make both programs work, /dev/video0 or 1 or 2 available?

step 1: resetting usb bus under linux using code:

/* few times it's resetting when use in bash loop it's not doing */ #include <stdio.h> #include <usb.h>  int main(int argc, char *argv[]) {   struct usb_bus *busses;   usb_init();   usb_find_busses();   usb_find_devices();   busses = usb_get_busses();   struct usb_bus *bus;   int c, i, a;   (bus = busses; bus; bus = bus->next) {     struct usb_device *dev;     int val;     usb_dev_handle *junk;     (dev = bus->devices; dev; dev = dev->next) {       char buf[1024];       junk = usb_open ( dev );       usb_get_string_simple(junk,2,buf,1023);        switch(argc) {        case 1:         if ( junk == null ) {           printf("can't open %p (%s)\n", dev, buf );         } else if (strcmp(buf,"hd pro webcam c920")==0) {           val = usb_reset(junk);           printf( "reset %p %d (%s)\n", dev, val, buf );         }         break;         default:         if ( junk == null ){           printf("can't open %p (%s)\n", dev, buf );         } else {           val = usb_reset(junk);           printf( "reset %p %d (%s)\n", dev, val, buf );         }       }        usb_close(junk);     }   } } 

step 2: running scanner - make sure video0 or 1 or 2 available, if not available resetting usb bus

#!/bin/bash j=true while $j   in 0 1 2       tmp="/dev/video$i"     if [ -e $tmp ]           echo "/dev/video$i"       j=false     else       echo "no - camera found - restarting usb $i"       echo root_password_to_execute | sudo -s /var/tmp/c-restartusb/restartusb     fi   done done echo "camera - logic ended, expecting camera available now" 

step 3: still it's not available?

no - camera found - restart usb 0 no - camera found - restart usb 1 no - camera found - restart usb 2 no - camera found - restart usb 0 no - camera found - restart usb 1 no - camera found - restart usb 2 no - camera found - restart usb 0 no - camera found - restart usb 1 no - camera found - restart usb 2 no - camera found - restart usb 0 no - camera found - restart usb 1 no - camera found - restart usb 2 no - camera found - restart usb 0 no - camera found - restart usb 1 no - camera found - restart usb 2 no - camera found - restart usb 0 no - camera found - restart usb 1 no - camera found - restart usb 2 no - camera found - restart usb 0 no - camera found - restart usb 1 no - camera found - restart usb 2 no - camera found - restart usb 0 no - camera found - restart usb 1 no - camera found - restart usb 2 no - camera found - restart usb 0 no - camera found - restart usb 1 no - camera found - restart usb 2 no - camera found - restart usb 0 no - camera found - restart usb 1 no - camera found - restart usb 2 no - camera found - restart usb 0 no - camera found - restart usb 1 no - camera found - restart usb 2 no - camera found - restart usb 0 no - camera found - restart usb 1 no - camera found - restart usb 2 no - camera found - restart usb 0 no - camera found - restart usb 1 no - camera found - restart usb 2 no - camera found - restart usb 0 no - camera found - restart usb 1 no - camera found - restart usb 2 no - camera found - restart usb 0 no - camera found - restart usb 1 no - camera found - restart usb 2 no - camera found - restart usb 0 no - camera found - restart usb 1 no - camera found - restart usb 2 no - camera found - restart usb 0 no - camera found - restart usb 1 no - camera found - restart usb 2 no - camera found - restart usb 0 no - camera found - restart usb 1 no - camera found - restart usb 2 no - camera found - restart usb 0 no - camera found - restart usb 1 no - camera found - restart usb 2 no - camera found - restart usb 0 no - camera found - restart usb 1 no - camera found - restart usb 2 no - camera found - restart usb 0 no - camera found - restart usb 1 no - camera found - restart usb 2 no - camera found - restart usb 0 no - camera found - restart usb 1 no - camera found - restart usb 2 no - camera found - restart usb 0 no - camera found - restart usb 1 no - camera found - restart usb 2 no - camera found - restart usb 0 no - camera found - restart usb 1 no - camera found - restart usb 2 no - camera found - restart usb 0 no - camera found - restart usb 1 no - camera found - restart usb 2 no - camera found - restart usb 0 no - camera found - restart usb 1 

don't sure reset usb code right...

can find usb device ?

if can, try below:

btw, code here. should work if can find usb node:

/* usbreset -- send usb port reset usb device */  #include <stdio.h> #include <unistd.h> #include <fcntl.h> #include <errno.h> #include <sys/ioctl.h>  #include <linux/usbdevice_fs.h>   int main(int argc, char **argv) {     const char *filename;     int fd;     int rc;      if (argc != 2) {         fprintf(stderr, "usage: usbreset device-filename\n");         return 1;     }     filename = argv[1];      fd = open(filename, o_wronly);     if (fd < 0) {         perror("error opening output file");         return 1;     }      printf("resetting usb device %s\n", filename);     rc = ioctl(fd, usbdevfs_reset, 0);     if (rc < 0) {         perror("error in ioctl");         return 1;     }     printf("reset successful\n");      close(fd);     return 0; } 

if can't, maybe want rescan find usb device this:

echo 1 > /sys/dev/block/8:16/device/rescan