[PATCH] drivers: spi: fix deref ater null.might in spi-uclass.c

[ant.v.moryakov@gmail.com]

From: Anton Moryakov <ant.v.moryakov@gmail.com>

The static analyzer (Svace) reported 
After having been compared to a NULL value at spi-uclass.c:465,
pointer 'dev' is passed as 1st parameter in call to function 'dev_get_flags' 
at spi-uclass.c:469, where it is dereferenced at device.h:240.

Correct explained:
1. Added dev && !device_active(dev) check before calling device_active()
2. Added explicit if (!dev) check with ret = -ENODEV setting
3. Protected logging in error block with if(dev) check

Signed-off-by: Anton Moryakov <ant.v.moryakov@gmail.com>
---
 drivers/spi/spi-uclass.c | 14 +++++++++++---
 1 file changed, 11 insertions(+), 3 deletions(-)

diff --git a/drivers/spi/spi-uclass.c b/drivers/spi/spi-uclass.c
index d6049753740..52b79223f96 100644
--- a/drivers/spi/spi-uclass.c
+++ b/drivers/spi/spi-uclass.c
@@ -345,7 +345,7 @@ int spi_get_bus_and_cs(int busnum, int cs, struct udevice **busp,
 		return ret;
 	}
 
-	if (!device_active(dev)) {
+	if (dev && !device_active(dev)) {
 		struct spi_slave *slave;
 
 		ret = device_probe(dev);
@@ -355,6 +355,11 @@ int spi_get_bus_and_cs(int busnum, int cs, struct udevice **busp,
 		slave->dev = dev;
 	}
 
+	if (!dev) {
+		ret = -ENODEV;
+		goto err;
+	}
+
 	slave = dev_get_parent_priv(dev);
 	bus_data = dev_get_uclass_priv(bus);
 
@@ -373,8 +378,11 @@ int spi_get_bus_and_cs(int busnum, int cs, struct udevice **busp,
 	return 0;
 
 err:
-	log_debug("%s: Error path, device '%s'\n", __func__, dev->name);
-
+	if(dev)
+		log_debug("%s: Error path, device '%s'\n", __func__, dev->name);
+	else
+		log_debug("%s: Error path, NULL device\n", __func__);
+	
 	return ret;
 }
 
-- 
2.30.2