Currently applications for devices which only are accessed from userspace
can use claim / release interface to make sure they don't get in each others
way. The same however does not work for applications which first need to detach
a "native" / in kernel driver, as this detach will not only detach native
drivers but also the usbfs driver, thus stealing the device from another
userspace / libusb app.

This patch fixes libusb_detach_kernel_driver to only detach "real" kernel
drivers and not the special usbfs driver used for userspace access to
USB devices. If the usbfs driver is found LIBUSB_ERROR_NOT_FOUND will be
returned to indicate no driver was detached.

Signed-off-by: Hans de Goede <hdego...@redhat.com>
---
 libusb/os/linux_usbfs.c | 6 ++++++
 1 file changed, 6 insertions(+)

diff --git a/libusb/os/linux_usbfs.c b/libusb/os/linux_usbfs.c
index dad7536..eee4967 100644
--- a/libusb/os/linux_usbfs.c
+++ b/libusb/os/linux_usbfs.c
@@ -1522,12 +1522,18 @@ static int op_detach_kernel_driver(struct 
libusb_device_handle *handle,
 {
        int fd = _device_handle_priv(handle)->fd;
        struct usbfs_ioctl command;
+       struct usbfs_getdriver getdrv;
        int r;
 
        command.ifno = interface;
        command.ioctl_code = IOCTL_USBFS_DISCONNECT;
        command.data = NULL;
 
+       getdrv.interface = interface;
+       r = ioctl(fd, IOCTL_USBFS_GETDRIVER, &getdrv);
+       if (r == 0 && strcmp(getdrv.driver, "usbfs") == 0)
+               return LIBUSB_ERROR_NOT_FOUND;
+
        r = ioctl(fd, IOCTL_USBFS_IOCTL, &command);
        if (r) {
                if (errno == ENODATA)
-- 
1.7.11.2


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