caif-xshm: Add CAIF driver for Shared memory for M7400
This patch introduces a caif shared memory link layer driver
for ST-Ericsson's Thor M7400 LTE modem.
M7400 uses a ring-buffer in shared memory for transporting data from the modem.
Each ring-buffer element contains an array of caif frames. caif_xshm calls
napi_schedule() when receiving notification about incoming data.
The napi-poll function copies data from the ring-buffer to SKBs until
ring-buffer is empty, or quota is exceeded.
If transmit ring-buffer is full, it also uses napi for scheduling transmission
of queued transmit buffer.
cc: David S. Miller <davem@davemloft.net> Acked-by: David S. Miller <davem@davemloft.net> Signed-off-by: Sjur Brændeland <sjur.brandeland@stericsson.com> Signed-off-by: Linus Walleij <linus.walleij@stericsson.com>