gpiolib: move validation of line handle flags into helper function

Move validation of line handle flags into helper function.
This reduces the size and complexity of linehandle_create and allows the
validation to be reused elsewhere.
Signed-off-by: Kent Gibson <warthog618@gmail.com>
Signed-off-by: Bartosz Golaszewski <bgolaszewski@baylibre.com>

drivers/gpio/gpiolib.c

@@ -428,6 +428,54 @@ struct linehandle_state {
 	GPIOHANDLE_REQUEST_OPEN_DRAIN | \
 	GPIOHANDLE_REQUEST_OPEN_SOURCE)
 
+static int linehandle_validate_flags(u32 flags)
+{
+	/* Return an error if an unknown flag is set */
+	if (flags & ~GPIOHANDLE_REQUEST_VALID_FLAGS)
+		return -EINVAL;
+
+	/*
+	 * Do not allow both INPUT & OUTPUT flags to be set as they are
+	 * contradictory.
+	 */
+	if ((flags & GPIOHANDLE_REQUEST_INPUT) &&
+	    (flags & GPIOHANDLE_REQUEST_OUTPUT))
+		return -EINVAL;
+
+	/*
+	 * Do not allow OPEN_SOURCE & OPEN_DRAIN flags in a single request. If
+	 * the hardware actually supports enabling both at the same time the
+	 * electrical result would be disastrous.
+	 */
+	if ((flags & GPIOHANDLE_REQUEST_OPEN_DRAIN) &&
+	    (flags & GPIOHANDLE_REQUEST_OPEN_SOURCE))
+		return -EINVAL;
+
+	/* OPEN_DRAIN and OPEN_SOURCE flags only make sense for output mode. */
+	if (!(flags & GPIOHANDLE_REQUEST_OUTPUT) &&
+	    ((flags & GPIOHANDLE_REQUEST_OPEN_DRAIN) ||
+	     (flags & GPIOHANDLE_REQUEST_OPEN_SOURCE)))
+		return -EINVAL;
+
+	/* Bias flags only allowed for input or output mode. */
+	if (!((flags & GPIOHANDLE_REQUEST_INPUT) ||
+	      (flags & GPIOHANDLE_REQUEST_OUTPUT)) &&
+	    ((flags & GPIOHANDLE_REQUEST_BIAS_DISABLE) ||
+	     (flags & GPIOHANDLE_REQUEST_BIAS_PULL_UP) ||
+	     (flags & GPIOHANDLE_REQUEST_BIAS_PULL_DOWN)))
+		return -EINVAL;
+
+	/* Only one bias flag can be set. */
+	if (((flags & GPIOHANDLE_REQUEST_BIAS_DISABLE) &&
+	     (flags & (GPIOHANDLE_REQUEST_BIAS_PULL_DOWN |
+			GPIOHANDLE_REQUEST_BIAS_PULL_UP))) ||
+	    ((flags & GPIOHANDLE_REQUEST_BIAS_PULL_DOWN) &&
+	     (flags & GPIOHANDLE_REQUEST_BIAS_PULL_UP)))
+		return -EINVAL;
+
+	return 0;
+}
+
 static long linehandle_ioctl(struct file *filep, unsigned int cmd,
 			     unsigned long arg)
 {
@@ -529,48 +577,9 @@ static int linehandle_create(struct gpio_device *gdev, void __user *ip)
 
 	lflags = handlereq.flags;
 
-	/* Return an error if an unknown flag is set */
-	if (lflags & ~GPIOHANDLE_REQUEST_VALID_FLAGS)
-		return -EINVAL;
-
-	/*
-	 * Do not allow both INPUT & OUTPUT flags to be set as they are
-	 * contradictory.
-	 */
-	if ((lflags & GPIOHANDLE_REQUEST_INPUT) &&
-	    (lflags & GPIOHANDLE_REQUEST_OUTPUT))
-		return -EINVAL;
-
-	/*
-	 * Do not allow OPEN_SOURCE & OPEN_DRAIN flags in a single request. If
-	 * the hardware actually supports enabling both at the same time the
-	 * electrical result would be disastrous.
-	 */
-	if ((lflags & GPIOHANDLE_REQUEST_OPEN_DRAIN) &&
-	    (lflags & GPIOHANDLE_REQUEST_OPEN_SOURCE))
-		return -EINVAL;
-
-	/* OPEN_DRAIN and OPEN_SOURCE flags only make sense for output mode. */
-	if (!(lflags & GPIOHANDLE_REQUEST_OUTPUT) &&
-	    ((lflags & GPIOHANDLE_REQUEST_OPEN_DRAIN) ||
-	     (lflags & GPIOHANDLE_REQUEST_OPEN_SOURCE)))
-		return -EINVAL;
-
-	/* Bias flags only allowed for input or output mode. */
-	if (!((lflags & GPIOHANDLE_REQUEST_INPUT) ||
-	      (lflags & GPIOHANDLE_REQUEST_OUTPUT)) &&
-	    ((lflags & GPIOHANDLE_REQUEST_BIAS_DISABLE) ||
-	     (lflags & GPIOHANDLE_REQUEST_BIAS_PULL_UP) ||
-	     (lflags & GPIOHANDLE_REQUEST_BIAS_PULL_DOWN)))
-		return -EINVAL;
-
-	/* Only one bias flag can be set. */
-	if (((lflags & GPIOHANDLE_REQUEST_BIAS_DISABLE) &&
-	     (lflags & (GPIOHANDLE_REQUEST_BIAS_PULL_DOWN |
-			GPIOHANDLE_REQUEST_BIAS_PULL_UP))) ||
-	    ((lflags & GPIOHANDLE_REQUEST_BIAS_PULL_DOWN) &&
-	     (lflags & GPIOHANDLE_REQUEST_BIAS_PULL_UP)))
-		return -EINVAL;
+	ret = linehandle_validate_flags(lflags);
+	if (ret)
+		return ret;
 
 	lh = kzalloc(sizeof(*lh), GFP_KERNEL);
 	if (!lh)