staging/easycap: Eliminate BKL

No locking is required for normal operation of the driver, but locking
is needed to prevent an Oops during some hot-unplugging scenarios.  The
BKL is replaced here by mutex locks together with traps to detect null
pointers following asynchronous device disconnection.

Signed-off-by: Mike Thomas <rmthomas@sciolus.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@suse.de>

drivers/staging/easycap/Kconfig

@@ -1,7 +1,6 @@
 config EASYCAP
 	tristate "EasyCAP USB ID 05e1:0408 support"
 	depends on USB && VIDEO_DEV
-	depends on BKL # please fix
 
 	---help---
 	  This is an integrated audio/video driver for EasyCAP cards with

drivers/staging/easycap/Makefile

@@ -10,4 +10,5 @@ ccflags-y := -Wall
 ccflags-y += -DEASYCAP_IS_VIDEODEV_CLIENT
 ccflags-y += -DEASYCAP_NEEDS_V4L2_DEVICE_H
 ccflags-y += -DEASYCAP_NEEDS_V4L2_FOPS
+ccflags-y += -DEASYCAP_NEEDS_UNLOCKED_IOCTL
 

drivers/staging/easycap/easycap.h

@@ -251,6 +251,12 @@ INTERLACE_MANY
  *  STRUCTURE DEFINITIONS
  */
 /*---------------------------------------------------------------------------*/
+struct easycap_dongle {
+struct easycap *peasycap;
+struct mutex mutex_video;
+struct mutex mutex_audio;
+};
+/*---------------------------------------------------------------------------*/
 struct data_buffer {
 struct list_head list_head;
 void *pgo;
@@ -491,7 +497,10 @@ struct data_buffer audio_buffer[];
 void             easycap_complete(struct urb *);
 int              easycap_open(struct inode *, struct file *);
 int              easycap_release(struct inode *, struct file *);
-long             easycap_ioctl(struct file *, unsigned int,  unsigned long);
+long             easycap_ioctl_noinode(struct file *, unsigned int, \
+								unsigned long);
+int              easycap_ioctl(struct inode *, struct file *, unsigned int, \
+								unsigned long);
 
 /*vvvvvvvvvvvvvvvvvvvvvvvvvvvvvvvvvvvvvvvvvvvvvvvvvvvvvvvvvvvvvvvvvvvvvvvvvv*/
 #if defined(EASYCAP_IS_VIDEODEV_CLIENT)
@@ -538,7 +547,10 @@ void             easysnd_complete(struct urb *);
 ssize_t          easysnd_read(struct file *, char __user *, size_t, loff_t *);
 int              easysnd_open(struct inode *, struct file *);
 int              easysnd_release(struct inode *, struct file *);
-long             easysnd_ioctl(struct file *, unsigned int,  unsigned long);
+long             easysnd_ioctl_noinode(struct file *, unsigned int, \
+								unsigned long);
+int              easysnd_ioctl(struct inode *, struct file *, unsigned int, \
+								unsigned long);
 unsigned int     easysnd_poll(struct file *, poll_table *);
 void             easysnd_delete(struct kref *);
 int              submit_audio_urbs(struct easycap *);

drivers/staging/easycap/easycap_debug.h

@@ -26,3 +26,4 @@
 /*****************************************************************************/
 extern int debug;
 extern int gain;
+extern struct easycap_dongle easycap_dongle[];