On Fri, 27 May 2005, Wakko Warner wrote:
> Any pointers on how to write this? I will be writing this in perl. The
> target system is mostly perl based (it's sorta like embedded but runs off a
> tmpfs filesystem)
Here is a program, dq.c, that demonstrates how to read the device
qualifier descriptor. It uses a local copy of the usb_ch9.h include file,
which is present in the kernel source under include/linux but was not
stored in /usr/include/linux on my system. Note that the program needs
root permission to run properly. It takes a single argument, which is the
/proc/bus/usb/BBB/DDD pathname for the device.
Alan Stern
#include <stdio.h>
#include <unistd.h>
#include <fcntl.h>
#include <errno.h>
#include <sys/ioctl.h>
#include <asm/byteorder.h>
#include <linux/usbdevice_fs.h>
typedef __u16 __le16; /* may not be needed */
#include "usb_ch9.h" /* may exist in /usr/include/linux */
int get_version(int fd)
{
struct usb_device_descriptor desc;
int n;
n = read(fd, &desc, sizeof(desc));
if (n < 0) {
perror("Error in read");
return n;
}
return __le16_to_cpu(desc.bcdUSB);
}
int get_qualifier(int fd)
{
struct usbdevfs_ctrltransfer ctrl;
struct usb_qualifier_descriptor desc;
int n;
ctrl.requesttype = USB_DIR_IN | USB_TYPE_STANDARD | USB_RECIP_DEVICE;
ctrl.request = USB_REQ_GET_DESCRIPTOR;
ctrl.value = USB_DT_DEVICE_QUALIFIER << 8;
ctrl.index = 0;
ctrl.length = sizeof(desc);
ctrl.timeout = 5000;
ctrl.data = &desc;
n = ioctl(fd, USBDEVFS_CONTROL, &ctrl);
if (n < 0) {
if (errno == EPIPE) /* Request not supported */
return 0;
perror("Error in USBDEVFS_CONTROL");
return n;
}
return 1;
}
int main(int argc, char **argv)
{
int fd;
int version;
int qualifier;
if (argc != 2) {
fprintf(stderr, "Usage: dq device_filename\n");
return 1;
}
fd = open(argv[1], O_RDWR);
if (fd < 0) {
perror("Error in open");
return 1;
}
version = get_version(fd);
if (version < 0)
return 1;
printf("USB version is 0x%04x.\n", version);
if (version < 0x0200)
return 2;
qualifier = get_qualifier(fd);
if (qualifier < 0)
return 1;
printf("Device %s high speed.\n",
qualifier ? "supports" : "does not support");
return 0;
}
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