spi: introduce master->handle_err() callback

This callback would be useful to handle an error that occurs in the generic
implementation of transfer_one_message(). The good candidate for this is to
drain FIFO and / or to terminate DMA transfers when timeout happened.

Signed-off-by: Andy Shevchenko <andriy.shevchenko@linux.intel.com>
Signed-off-by: Mark Brown <broonie@kernel.org>

drivers/spi/spi.c

@@ -851,6 +851,9 @@ out:
 	if (msg->status == -EINPROGRESS)
 		msg->status = ret;
 
+	if (msg->status)
+		master->handle_err(master, msg);
+
 	spi_finalize_current_message(master);
 
 	return ret;

include/linux/spi/spi.h

@@ -294,6 +294,8 @@ static inline void spi_unregister_driver(struct spi_driver *sdrv)
  *                    transfer_one_message are mutually exclusive; when both
  *                    are set, the generic subsystem does not call your
  *                    transfer_one callback.
+ * @handle_err: the subsystem calls the driver to handle and error that occurs
+ *		in the generic implementation of transfer_one_message().
  * @unprepare_message: undo any work done by prepare_message().
  * @cs_gpios: Array of GPIOs to use as chip select lines; one per CS
  *	number. Any individual value may be -ENOENT for CS lines that
@@ -448,6 +450,8 @@ struct spi_master {
 	void (*set_cs)(struct spi_device *spi, bool enable);
 	int (*transfer_one)(struct spi_master *master, struct spi_device *spi,
 			    struct spi_transfer *transfer);
+	void (*handle_err)(struct spi_master *master,
+			   struct spi_message *message);
 
 	/* gpio chip select */
 	int			*cs_gpios;