How compile a user space program with kernel headers

Question

I need to test a usbfs device by using ioctl. I need use ioctl(fd, USBDEVFS_REAPURBNDELAY, &receive);. But USBDEVFS_REAPURBNDELAY is defined in a kernel header, so I include some kernel file like that:

#include <linux/usb.h>
#include <linux/usbdevice_fs.h>
#include <asm/byteorder.h>
#include <linux/usb/ch9.h>

and compile it with gcc -g -I /usr/src/linux-3.4.4-2-pae/include/ -o /home/madper/kernel/usb/select_for_usb /home/madper/kernel/usb/select_for_usb.c

It said #warning "Attempt to use kernel headers from user space, see http://kernelnewbies.org/KernelHeaders" [-Wcpp]

And folled by lots of errors, so, What's the right way to use kernel headers?

/usr/src/linux-3.4.4-2-pae/include/linux/mod_devicetable.h:21:2: error: unknown type name ‘kernel_ulong_t’
/usr/src/linux-3.4.4-2-pae/include/linux/mod_devicetable.h:36:2: error: unknown type name ‘kernel_ulong_t’
/usr/src/linux-3.4.4-2-pae/include/linux/mod_devicetable.h:37:33: error: ‘kernel_ulong_t’ undeclared here (not in a function)
/usr/src/linux-3.4.4-2-pae/include/linux/mod_devicetable.h:37:3: error: requested alignment is not an integer constant
/usr/src/linux-3.4.4-2-pae/include/linux/mod_devicetable.h:119:2: error: expected specifier-qualifier-list before ‘kernel_ulong_t’
/usr/src/linux-3.4.4-2-pae/include/linux/mod_devicetable.h:141:2: error: expected specifier-qualifier-list before ‘kernel_ulong_t’
/usr/src/linux-3.4.4-2-pae/include/linux/mod_devicetable.h:154:2: error: expected specifier-qualifier-list before ‘kernel_ulong_t’
/usr/src/linux-3.4.4-2-pae/include/linux/mod_devicetable.h:168:2: error: expected specifier-qualifier-list before ‘kernel_ulong_t’
/usr/src/linux-3.4.4-2-pae/include/linux/mod_devicetable.h:179:2: error: expected specifier-qualifier-list before ‘kernel_ulong_t’
/usr/src/linux-3.4.4-2-pae/include/linux/mod_devicetable.h:187:2: error: expected specifier-qualifier-list before ‘kernel_ulong_t’
/usr/src/linux-3.4.4-2-pae/include/linux/mod_devicetable.h:195:2: error: expected specifier-qualifier-list before ‘kernel_ulong_t’
/usr/src/linux-3.4.4-2-pae/include/linux/mod_devicetable.h:200:2: error: expected specifier-qualifier-list before ‘kernel_ulong_t’
/usr/src/linux-3.4.4-2-pae/include/linux/mod_devicetable.h:227:2: error: expected specifier-qualifier-list before ‘kernel_ulong_t’
/usr/src/linux-3.4.4-2-pae/include/linux/mod_devicetable.h:260:2: error: expected specifier-qualifier-list before ‘kernel_ulong_t’
/usr/src/linux-3.4.4-2-pae/include/linux/mod_devicetable.h:314:2: error: expected specifier-qualifier-list before ‘kernel_ulong_t’
/usr/src/linux-3.4.4-2-pae/include/linux/mod_devicetable.h:341:2: error: expected specifier-qualifier-list before ‘kernel_ulong_t’
/usr/src/linux-3.4.4-2-pae/include/linux/mod_devicetable.h:366:2: error: expected specifier-qualifier-list before ‘kernel_ulong_t’
/usr/src/linux-3.4.4-2-pae/include/linux/mod_devicetable.h:413:2: error: expected specifier-qualifier-list before ‘kernel_ulong_t’
/usr/src/linux-3.4.4-2-pae/include/linux/mod_devicetable.h:433:2: error: expected specifier-qualifier-list before ‘kernel_ulong_t’
/usr/src/linux-3.4.4-2-pae/include/linux/mod_devicetable.h:444:2: error: expected specifier-qualifier-list before ‘kernel_ulong_t’
/usr/src/linux-3.4.4-2-pae/include/linux/mod_devicetable.h:479:2: error: expected specifier-qualifier-list before ‘kernel_ulong_t’
/usr/src/linux-3.4.4-2-pae/include/linux/mod_devicetable.h:508:2: error: expected specifier-qualifier-list before ‘kernel_ulong_t’
/usr/src/linux-3.4.4-2-pae/include/linux/mod_devicetable.h:540:2: error: expected specifier-qualifier-list before ‘kernel_ulong_t’
/usr/src/linux-3.4.4-2-pae/include/linux/mod_devicetable.h:551:2: error: expected specifier-qualifier-list before ‘kernel_ulong_t’
/usr/src/linux-3.4.4-2-pae/include/linux/mod_devicetable.h:566:2: error: expected specifier-qualifier-list before ‘kernel_ulong_t’
/usr/src/linux-3.4.4-2-pae/include/linux/mod_devicetable.h:582:2: error: expected specifier-qualifier-list before ‘kernel_ulong_t’
/home/madper/kernel/usb/select_for_usb.c: In function ‘main’:
/home/madper/kernel/usb/select_for_usb.c:46:30: error: expected expression before ‘void’

Answer 1

You really shouldn't have to include kernel headers directly. In some cases it is necessary and probably the best way to handle it is to grab a copy of the kernel headers and hack out just the parts you need. But in this case I'm not sure I understand why you need kernel headers. Why doesn't it work just to include <linux/usbdevice_fs.h>?

On all the systems I looked at (a couple of different Ubuntu systems and one RHEL 6 system) that file can be included from userspace and has the define of USBDEVFS_REAPURBNDELAY. I tried

#include <stdio.h>
#include <sys/ioctl.h>
#include <linux/usbdevice_fs.h>

int main()
{
    printf("USBDEVFS_REAPURBNDELAY is %ld\n", USBDEVFS_REAPURBNDELAY);
    return 0;
}

and I can build it cleanly and when I run it I get

USBDEVFS_REAPURBNDELAY is 1074287885

so at least based on what you wrote above, you don't need any kernel headers for that ioctl define. I suspect anything else you think you need for userspace USB stuff is similarly exported to userspace in a clean header.

Answer 2

You can't use kernel headers for user programs. Even if you do by some means it is strongly discouraged. Check the below link for more clarification.

http://lwn.net/Articles/113349/

If you do want to control usb devices from user space look at libusb.