From 3e17ef2b55d80237da9766f3464ae784448a23e6 Mon Sep 17 00:00:00 2001
From: Steve Markgraf <steve@steve-m.de>
Date: Tue, 4 Jun 2013 14:47:16 +0200
Subject: lib: don't detach kernel driver by default

Since this feature also disconnects running instances
of librtlsdr that claimed the device, it is now disabled
by default and can only be enabled at compile time.

To enable it when building with cmake:
cmake . -DDETACH_KERNEL_DRIVER=ON

To enable it when building with automake:
./configure --enable-driver-detach

Signed-off-by: Steve Markgraf <steve@steve-m.de>
---
 CMakeLists.txt  |  8 ++++++++
 configure.ac    |  6 ++++++
 src/librtlsdr.c | 12 ++++++++++++
 3 files changed, 26 insertions(+)

diff --git a/CMakeLists.txt b/CMakeLists.txt
index 09a9cbb..13a7d6f 100644
--- a/CMakeLists.txt
+++ b/CMakeLists.txt
@@ -111,6 +111,14 @@ else (INSTALL_UDEV_RULES)
     message (STATUS "Udev rules not being installed, install them with -DINSTALL_UDEV_RULES=ON")
 endif (INSTALL_UDEV_RULES)
 
+option(DETACH_KERNEL_DRIVER "Detach kernel driver if loaded" OFF)
+if (DETACH_KERNEL_DRIVER)
+    message (STATUS "Building with kernel driver detaching enabled")
+    add_definitions(-DDETACH_KERNEL_DRIVER=1)
+else (DETACH_KERNEL_DRIVER)
+    message (STATUS "Building with kernel driver detaching disabled, use -DDETACH_KERNEL_DRIVER=ON to enable")
+endif (DETACH_KERNEL_DRIVER)
+
 ########################################################################
 # Add subdirectories
 ########################################################################
diff --git a/configure.ac b/configure.ac
index 954d2ef..ce47d89 100644
--- a/configure.ac
+++ b/configure.ac
@@ -64,6 +64,12 @@ AC_TRY_COMPILE([],[],
   AC_MSG_RESULT(no)
   CFLAGS="$old_CFLAGS")
 
+AC_ARG_ENABLE(driver-detach,
+[  --enable-driver-detach          Enable detaching of kernel driver (disabled by default)],
+[if test x$enableval = xyes; then
+    CFLAGS="$CFLAGS -DDETACH_KERNEL_DRIVER"
+fi])
+
 dnl Generate the output
 AC_CONFIG_HEADER(config.h)
 
diff --git a/src/librtlsdr.c b/src/librtlsdr.c
index 2f5d90a..ddebb48 100644
--- a/src/librtlsdr.c
+++ b/src/librtlsdr.c
@@ -1351,12 +1351,22 @@ int rtlsdr_open(rtlsdr_dev_t **out_dev, uint32_t index)
 
 	if (libusb_kernel_driver_active(dev->devh, 0) == 1) {
 		dev->driver_active = 1;
+
+#ifdef DETACH_KERNEL_DRIVER
 		if (!libusb_detach_kernel_driver(dev->devh, 0)) {
 			fprintf(stderr, "Detached kernel driver\n");
 		} else {
 			fprintf(stderr, "Detaching kernel driver failed!");
 			goto err;
 		}
+#else
+		fprintf(stderr, "\nKernel driver is active, or device is "
+				"claimed by second instance of librtlsdr."
+				"\nIn the first case, please either detach"
+				" or blacklist the kernel module\n"
+				"(dvb_usb_rtl28xxu), or enable automatic"
+				" detaching at compile time.\n\n");
+#endif
 	}
 
 	r = libusb_claim_interface(dev->devh, 0);
@@ -1484,12 +1494,14 @@ int rtlsdr_close(rtlsdr_dev_t *dev)
 
 	libusb_release_interface(dev->devh, 0);
 
+#ifdef DETACH_KERNEL_DRIVER
 	if (dev->driver_active) {
 		if (!libusb_attach_kernel_driver(dev->devh, 0))
 			fprintf(stderr, "Reattached kernel driver\n");
 		else
 			fprintf(stderr, "Reattaching kernel driver failed!\n");
 	}
+#endif
 
 	libusb_close(dev->devh);
 
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