caif: Add support for flow-control on device's tx-queue
caif: Add support for flow-control on device's tx-queue

Flow control is implemented by inspecting the qdisc queue length
in order to detect potential overflow on the TX queue. When a threshold
is reached flow-off is sent upwards in the CAIF stack. At the same time
the skb->destructor is hi-jacked by orphaning the SKB and the original
destructor is replaced with a "flow-on" callback. When the "hi-jacked"
SKB is consumed the queue should be empty, and the "flow-on" callback
is called and xon is sent upwards in the CAIF stack.

Signed-off-by: Sjur Brændeland <90c9f68dc7b20ac89683f2c4f55e4a05e8dbf9ad@stericsson.com>
Signed-off-by: David S. Miller <fe08d3c717adf2ae63592e4c9aec6e3e404d8e3e@davemloft.net>

KristFoundation/Programs,TeamVee-Kanas/android_kernel_samsung_kanas,TeamVee-Kanas/android_kernel_samsung_kanas,KristFoundation/Programs,TeamVee-Kanas/android_kernel_samsung_kanas,TeamVee-Kanas/android_kernel_samsung_kanas,KristFoundation/Programs,KristFoundation/Programs,KristFoundation/Programs,KristFoundation/Programs,TeamVee-Kanas/android_kernel_samsung_kanas