spi/bitbang: check for setup_transfer during initialization

setup_transfer is mandatory if spi_bitbang_transfer is used, so
check for it during initialization and not each time during runtime.
Signed-off-by: Sascha Hauer <s.hauer@pengutronix.de>
Signed-off-by: Uwe Kleine-König <u.kleine-koenig@pengutronix.de>
Signed-off-by: Grant Likely <grant.likely@secretlab.ca>

drivers/spi/spi_bitbang.c

@@ -259,10 +259,6 @@ static void bitbang_work(struct work_struct *work)
 	struct spi_bitbang	*bitbang =
 		container_of(work, struct spi_bitbang, work);
 	unsigned long		flags;
-	int			(*setup_transfer)(struct spi_device *,
-					struct spi_transfer *);
-
-	setup_transfer = bitbang->setup_transfer;
 
 	spin_lock_irqsave(&bitbang->lock, flags);
 	bitbang->busy = 1;
@@ -300,11 +296,7 @@ static void bitbang_work(struct work_struct *work)
 
 			/* init (-1) or override (1) transfer params */
 			if (do_setup != 0) {
-				if (!setup_transfer) {
-					status = -ENOPROTOOPT;
-					break;
-				}
-				status = setup_transfer(spi, t);
+				status = bitbang->setup_transfer(spi, t);
 				if (status < 0)
 					break;
 				if (do_setup == -1)
@@ -465,6 +457,9 @@ int spi_bitbang_start(struct spi_bitbang *bitbang)
 		}
 	} else if (!bitbang->master->setup)
 		return -EINVAL;
+	if (bitbang->master->transfer == spi_bitbang_transfer &&
+			!bitbang->setup_transfer)
+		return -EINVAL;
 
 	/* this task is the only thing to touch the SPI bits */
 	bitbang->busy = 0;