HIDAPI does not recognize "virtual" HID device

[tuxedo-wse]

So with this driver https://git.kernel.org/pub/scm/linux/kernel/git/next/linux-next.git/commit/?id=cfd84b3f419bf0aec60ecddc92c61b539c339ec9 there is a virtual HID device i.e. a hid device that exists just in software and is not connected to a bus.

HIDAPI does net seems to recognize this.

My minimal test code:

#include <stdio.h>
#include <hidapi/hidapi.h>

int main() {
    printf("HID Devices:\n");
    struct hid_device_info *devi, *dev = hid_enumerate(0, 0);
    devi = dev;
    while(devi != NULL) {
        printf("%04x:%04x\n", devi->vendor_id, devi->product_id);
        devi = devi->next;
    }
    hid_free_enumeration(dev);
}

Compiled with gcc test.c -lhidapi-hidraw for the hidraw interface, this does not liste the device, while /sys/class/hidraw/ has the device.

[mcuee]

Does this device show up as /dev/hidraw*? If this device is not a USB hid device and yet not show up as hidraw device, then hidapi cannot find it.

Also you need to have permission. You may want to try to run as sudo to see if that helps.

[mcuee]

Basically you can run the Linux kernel hid-example to see if that works or not.
https://github.com/torvalds/linux/blob/master/samples/hidraw/hid-example.c

[tuxedo-wse]

Does this device show up as /dev/hidraw*?

Yes

Also you need to have permission. You may want to try to run as sudo to see if that helps.

I did that but didn't help

[tuxedo-wse]

More testing using hid_open_path:

#include <stdio.h>

#include <hidapi/hidapi.h>

int main() {
    printf("HID Devices:\n");
    struct hid_device_info *devi, *dev = hid_enumerate(0, 0);
    devi = dev;
    while(devi != NULL) {
        printf("%04x:%04x\n", devi->vendor_id, devi->product_id);
        devi = devi->next;
    }
    hid_free_enumeration(dev);

    hid_device *foo = hid_open_path("/dev/hidraw2");
    devi = hid_get_device_info(foo);
    printf("\n%04x:%04x\n", devi->vendor_id, devi->product_id);
    hid_close(foo);

    foo = hid_open_path("/dev/hidraw3");
    devi = hid_get_device_info(foo);
    printf("\n%04x:%04x\n", devi->vendor_id, devi->product_id);
    hid_close(foo);
}

Both /dev/hidraw2 and /dev/hidraw3 exist and i run the programm with root.

hidraw2 is a normal physical device (I think the usb keyboard), hidraw3 is the virtual device from the driver.

The hidraw 2 example works fine while the hidraw3 example crashes as the printf step

[tuxedo-wse]

hid_error tells me "couldn't create hid_device_info"

[tuxedo-wse]

Following that trace my educated guess is that the culprit is this switch statement:

hidapi/linux/hid.c

Line 716 in d6b2a97

switch (bus_type) {

It expects the bus type to be USB, BT, I2C, or SPI, but this device is none of that (in the kernel driver it is specified it as BUS_VIRTUAL https://git.kernel.org/pub/scm/linux/kernel/git/next/linux-next.git/tree/drivers/platform/x86/tuxedo/nb04/wmi_ab.c?id=cfd84b3f419bf0aec60ecddc92c61b539c339ec9#n841 , I guess that is the same define that is asked for here?)

[tuxedo-wse]

there is a switch statement before that with a clear comment:

hidapi/linux/hid.c

Line 680 in d6b2a97

/* Filter out unhandled devices right away */