greybus: don't assume subdevs are valid

Most of the disconnect routines for the "subdevs" of a module
blindly assume that initialization of the subdev was successful.

Fix this by checking for null pointers.

Signed-off-by: Alex Elder <elder@linaro.org>
Signed-off-by: Greg Kroah-Hartman <greg@kroah.com>
greybus: unlock gbuf mutex on free

To drop a reference on a gbuf, greybus_free_gbuf() is called.  That
uses kref_put_mutex() to drop the refernce under protection of
gbuf_mutex.  However the release routine, free_gbuf(), never
releases the mutex as it should.  Fix that.

Signed-off-by: Alex Elder <elder@linaro.org>
Signed-off-by: Greg Kroah-Hartman <greg@kroah.com>
greybus: unlock hd mutex on free

When free_hd() is called, hd_mutex is held.  It is the
responsibility of free_hd() to drop that mutex.

Signed-off-by: Alex Elder <elder@linaro.org>
Signed-off-by: Greg Kroah-Hartman <greg@kroah.com>
greybus: don't restrict input buffer size

Don't assume that input buffers have any particular content.  The
only thing the gbuf layer needs to be concerned with is the presence
of the cport_id byte at the beginning of a transfer.

Signed-off-by: Alex Elder <elder@linaro.org>
Signed-off-by: Greg Kroah-Hartman <greg@kroah.com>
greybus: zero all data buffers

Don't assume the buffer data area will all be overwritten.  Zero all
buffer space, to avoid sending crap over the wire.

Signed-off-by: Alex Elder <elder@linaro.org>
Signed-off-by: Greg Kroah-Hartman <greg@kroah.com>