[PATCH 3.16.y-ckt 045/110] spi: bitbang: Make setup_transfer() callback optional

[Luis Henriques]

3.16.7-ckt13 -stable review patch.  If anyone has any objections, please let me know.

------------------

From: Pelle Nilsson <per.nilsson at xelmo.com>

commit 7d0ec8b6f40b356f780b79de63eeafd6b907d68c upstream.

Some controller drivers have no need of this callback (spi-altera even
causes a NULL pointer dereference because it doesn't register the callback,
falsely assuming that it is already optional).

Fixes: 30af9b558a56 ("spi/bitbang: Drop empty setup() functions")
Signed-off-by: Pelle Nilsson <per.nilsson at xelmo.com>
Reviewed-by: Ezequiel Garcia <ezequiel.garcia at vanguardiasur.com.ar>
Signed-off-by: Mark Brown <broonie at kernel.org>
Signed-off-by: Luis Henriques <luis.henriques at canonical.com>
---
 drivers/spi/spi-bitbang.c | 17 ++++++++++-------
 1 file changed, 10 insertions(+), 7 deletions(-)

diff --git a/drivers/spi/spi-bitbang.c b/drivers/spi/spi-bitbang.c
index dc7d2c2d643e..fecdda270c5d 100644
--- a/drivers/spi/spi-bitbang.c
+++ b/drivers/spi/spi-bitbang.c
@@ -184,7 +184,6 @@ int spi_bitbang_setup(struct spi_device *spi)
 {
 	struct spi_bitbang_cs	*cs = spi->controller_state;
 	struct spi_bitbang	*bitbang;
-	int			retval;
 	unsigned long		flags;
 
 	bitbang = spi_master_get_devdata(spi->master);
@@ -201,9 +200,11 @@ int spi_bitbang_setup(struct spi_device *spi)
 	if (!cs->txrx_word)
 		return -EINVAL;
 
-	retval = bitbang->setup_transfer(spi, NULL);
-	if (retval < 0)
-		return retval;
+	if (bitbang->setup_transfer) {
+		int retval = bitbang->setup_transfer(spi, NULL);
+		if (retval < 0)
+			return retval;
+	}
 
 	dev_dbg(&spi->dev, "%s, %u nsec/bit\n", __func__, 2 * cs->nsecs);
 
@@ -299,9 +300,11 @@ static int spi_bitbang_transfer_one(struct spi_master *master,
 
 		/* init (-1) or override (1) transfer params */
 		if (do_setup != 0) {
-			status = bitbang->setup_transfer(spi, t);
-			if (status < 0)
-				break;
+			if (bitbang->setup_transfer) {
+				status = bitbang->setup_transfer(spi, t);
+				if (status < 0)
+					break;
+			}
 			if (do_setup == -1)
 				do_setup = 0;
 		}