On 8 Jan 2007, Mattias Rönnblom wrote:
> Hi,
>
> is there a way to turn off USB devices from user-space?
No. However there is a way to suspend a USB device. In order to use it,
you must have a kernel with CONFIG_PM_SYSFS_DEPRECATED turned on. To
suspend a device, do (as root):
echo -n 2 >/sys/bus/usb/devices/.../power/state
where the "..." is the ID for your device. To unsuspend, do the same
thing but with a "0" instead of the "2" above.
Note that this mechanism is slated to be removed from the kernel within
the next year. Hopefully some other mechanism will take its place.
> To reset a
> device?
Here's a program to do it. You invoke it as either
usbreset /proc/bus/usb/BBB/DDD
or
usbreset /dev/usbB.D
depending on how your system is set up, where BBB and DDD are the bus and
device address numbers.
Alan Stern
-------------------
/* usbreset -- send a USB port reset to a 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;
}
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