CODEWITHSUNDEEP
clinuxlinux-kerneloperating-systemlinux-device-driver
Debesh Mohanty
Debesh Mohanty

Reputation: 489

struct usb_device_id does not contain USB device information

I am new to Linux kernel and I am presently learning USB device drivers. I wrote a simple USB driver with probe callback and disconnect callback functions.

In the probe callback I try to display values of the struct usb_device_id argument passed to it. The problem is that structure variable shows product id and vendor id as 0.

What is the reason for this? Am I doing all right?

The code snippets from the driver are

#include<linux/init.h>
#include<linux/kernel.h>
#include<linux/module.h>
#include<linux/usb.h>

int probe_callback(struct usb_interface *intf, const struct usb_device_id *id);
void disconnect_callback(struct usb_interface *intf);

struct usb_device_id usb_ids[]={
    {.driver_info=42},
    {}
};

struct usb_driver USB_DRIVER={
    .name="NEW USB",
    .id_table=usb_ids,
    .probe=probe_callback,
    .disconnect=disconnect_callback
};

//PROBLEM IS IN THE FUNCTION BELOW .....................

int probe_callback(struct usb_interface *intf, const struct usb_device_id *id)
{
    printk(KERN_ALERT "probe callback\n");
    __u16 vendor_id=id->idVendor;
    __u16 product_id=id->idProduct;
    printk("product id : %x vendor id : %x\n", product_id, vendor_id);
    return 0;
}

//..........................

void disconnect_callback(struct usb_interface *intf)
{
    printk(KERN_ALERT "disconnect callback\n");
}

static int start(void)
{
    printk(KERN_ALERT "module registered\n");
    int result;
    result=usb_register(&USB_DRIVER);
    if(result)
    {
            printk("error in registering usb driver...Error code = %d\n", result);
    }
    return result;
}

static void stop(void)
{
    printk(KERN_ALERT "module unregistered\n");
    usb_deregister(&USB_DRIVER);
}

module_init(start);  
module_exit(stop);

The logs I get when I execute dmesg are

[ 1539.714265] probe callback
[ 1539.714277] product id : 0 vendor id : 0

Thanks in advance for any help

Upvotes: 1

Views: 847

Answers (1)

Ian Abbott
Ian Abbott

Reputation: 17403

Your usb_id table does not contain vendor and product IDs. The id pointer passed to your probe_callback points to the element of usb_id that matched the device being probed.

You need to fill in the elements of your usb_id table properly to match the devices you are interested in, for example using the USB_DEVICE(vend, prod) macro.

Upvotes: 4

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