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Newby3

Member

Registered: 2012-05-28

Posts: 2

USB Raw hid

I am trying to write code to communicate with a USB device using Raw HID and am having some issues.  I am getting a segmentation fault because i can't access the memory of the usb_interface struct.  The pointers appear to be good and i am able to get a bunch of information about the USB device, This code works in other linux distributions, so im wondering if maybe i dont have something set up/installed right?  Im not sure what to try next so any help would be appreciated.  Thanks

int rawhid_open(int max, int vid, int pid, int usage_page, int usage)
{
        printf("%s:%d\n", __FILE__, __LINE__);
	struct usb_bus *bus;
	struct usb_device *dev;
	struct usb_interface *iface;
	struct usb_interface_descriptor *desc;
	struct usb_endpoint_descriptor *ep;
	usb_dev_handle *u;
	uint8_t buf[1024], *p;
	int i, n, len, tag, ep_in, ep_out, count=0, claimed;
	uint32_t val=0, parsed_usage, parsed_usage_page;
	hid_t *hid;

	if (first_hid) free_all_hid();
	printf("rawhid_open, max=%d\n", max);
	if (max < 1) return 0;
	usb_init();
	usb_find_busses();
	usb_find_devices();
	for (bus = usb_get_busses(); bus; bus = bus->next) {
		for (dev = bus->devices; dev; dev = dev->next) {
			if (vid > 0 && dev->descriptor.idVendor != vid) continue;
			if (pid > 0 && dev->descriptor.idProduct != pid) continue;
			if (!dev->config) continue;
			if (dev->config->bNumInterfaces < 1) continue;
			printf("device: vid=%04X, pic=%04X, with %d iface\n",
				dev->descriptor.idVendor,
				dev->descriptor.idProduct,
				dev->config->bNumInterfaces);
			iface = dev->config->interface;
                        u = NULL;
			claimed = 0;
			for (i=0; i<dev->config->bNumInterfaces && iface; i++, iface++) {
			        printf("%s:%d\n", __FILE__, __LINE__);

				desc = iface->altsetting;  //SEGMENTATION FAULT HERE

				printf("I dont get here. %s:%d\n", __FILE__, __LINE__);


(gdb) print/x dev->descriptor.idVendor
$12 = 0x16c0
(gdb) print/x dev->descriptor.idProduct
$13 = 0x486
(gdb) print/x dev->config->bNumInterfaces
$14 = 0x8
(gdb) print/x dev->config->interface
$15 = 0x21
(gdb) print/x iface
$16 = 0x21
(gdb) print/x iface->altsetting
Cannot access memory at address 0x21
(gdb) step

Program received signal SIGSEGV, Segmentation fault.
0x000091f8 in rawhid_open (max=1, vid=5824, pid=1158, usage_page=65451,
    usage=512) at hid_LINUX.c:202
202                                     desc = iface->altsetting;

Last edited by Inxsible (2012-06-01 15:32:42)

Themaister

Member

From: Trondheim, Norway

Registered: 2008-07-21

Posts: 652

Website

Re: USB Raw hid

Any reason you're using legacy libusb rather than libusb 1.0?

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@ GitHub

Newby3

Member

Registered: 2012-05-28

Posts: 2

Re: USB Raw hid

Only because i could reuse some code that uses libusb 0.1,  I think ill try using libusb 1.0 and see how that goes.

Inxsible

Forum Fellow

From: Chicago

Registered: 2008-06-09

Posts: 9,183

Re: USB Raw hid

Newby3, please use code tags when posting large/long code snippets. Makes it easier to read. I have edited your post this time.

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