SUMMARY:
Many potential crashes when unplugging the camera while it's in use are fixed.
OV7620/OV7120 greyscale mode is fixed too.

PER-FILE CHANGES:
(+: New, -: Removed, *: Cleanup, @: Bugfix, =: Sync with kernel)

[ov511.c]
@ Fix race condition: close() and disconnect() could be called at the same time
  causing a double-free of struct usb_ov511
@ Prevent synchronous control messages from being sent after their transfer
  buffer is deallocated
+ Prevent bogus I2C error messages during device detection
* Get rid of some unnecessary checks for !ov and !ov->dev. The checks were
  already performed after taking ov->lock further up the call stack.
+ Add some checks for !ov->dev in open() and elsewhere
* Remove unnecessary calls to ov51x_dealloc() in close() and disconnect()
@ Return -ENODEV instead of -EIO if device was disconnected
@ In cases where the driver sleeps under ov->lock, check for !ov->present
  instead of !ov->dev after waking up. This is because ov->dev can't go NULL
  while ov->lock is taken, since that would make lots of other code unsafe.
* Consolidate I2C detection code into ovsensor_probe()
@  Remove unnecessary call to destroy_proc_ov511_cam() in probe() error path

[ov511.h]
+ Add struct usb_ov511.present

[ov7x20.c]
@ Fix greyscale mode: don't put sensor into 8-bit mode

[ovfx2.c]
- Get rid of some more leftovers from ov511.c
@ Fix race condition: close() and disconnect() could be called at the same time
  causing a double-free of struct usb_ovfx2
@ Prevent synchronous control messages from being sent after their transfer
  buffer is deallocated. This requires taking ov->cbuf_lock as a barrier against
  disconnect() finishing even in places where cbuf isn't actually used.
+ Prevent bogus I2C error messages during device detection
* Get rid of some unnecessary checks for !ov and !ov->dev. The checks were
  already performed after taking ov->lock further up the call stack.
- Remove unused interleave() functions, since they turned out to be unnecessary
+ Add some checks for !ov->dev in open() and elsewhere
* Remove unnecessary calls to ovfx2_dealloc() in close() and disconnect()
@ Return -ENODEV instead of -EIO if device was disconnected
@ In cases where the driver sleeps under ov->lock, check for !ov->present
  instead of !ov->dev after waking up. This is because ov->dev can't go NULL
  while ov->lock is taken, since that would make lots of other code unsafe.
* Consolidate I2C detection code into ovsensor_probe(). This is a simplified
  version of ovsensor_probe() from ov511.c

[ovsensor.c]
@ Set state before calling schedule_timeout() to prevent busy-looping