media: dvb_frontend: split dvb_frontend_handle_ioctl function

Over time, dvb_frontend_handle_ioctl() has grown to the point where
we now get a warning from the compiler about excessive stack usage:

drivers/media/dvb-core/dvb_frontend.c: In function 'dvb_frontend_handle_ioctl':
drivers/media/dvb-core/dvb_frontend.c:2692:1: error: the frame size of 1048 bytes is larger than 1024 bytes [-Werror=frame-larger-than=]

Almost all of this is used by the dtv_frontend_properties structure
in the FE_GET_PROPERTY and FE_GET_FRONTEND commands. Splitting those
into separate function reduces the stack usage of the main function
to just 136 bytes, the others are under 500 each.
Signed-off-by: Arnd Bergmann <arnd@arndb.de>
Signed-off-by: Sean Young <sean@mess.org>
Signed-off-by: Mauro Carvalho Chehab <mchehab+samsung@kernel.org>

drivers/media/dvb-core/dvb_frontend.c

@@ -2311,21 +2311,15 @@ static int dtv_set_frontend(struct dvb_frontend *fe)
 	return 0;
 }
 
-static int dvb_frontend_handle_ioctl(struct file *file,
-				     unsigned int cmd, void *parg)
+static int dvb_get_property(struct dvb_frontend *fe, struct file *file,
+			    struct dtv_properties *tvps)
 {
-	struct dvb_device *dvbdev = file->private_data;
-	struct dvb_frontend *fe = dvbdev->priv;
 	struct dvb_frontend_private *fepriv = fe->frontend_priv;
-	struct dtv_frontend_properties *c = &fe->dtv_property_cache;
-	int i, err = -ENOTSUPP;
-
-	dev_dbg(fe->dvb->device, "%s:\n", __func__);
-
-	switch (cmd) {
-	case FE_SET_PROPERTY: {
-		struct dtv_properties *tvps = parg;
 	struct dtv_property *tvp = NULL;
+	struct dtv_frontend_properties getp;
+	int i, err;
+
+	memcpy(&getp, &fe->dtv_property_cache, sizeof(getp));
 
 	dev_dbg(fe->dvb->device, "%s: properties.num = %d\n",
 		__func__, tvps->num);
@@ -2336,30 +2330,74 @@ static int dvb_frontend_handle_ioctl(struct file *file,
 	 * Put an arbitrary limit on the number of messages that can
 	 * be sent at once
 	 */
-		if (!tvps->num || (tvps->num > DTV_IOCTL_MAX_MSGS))
+	if (!tvps->num || tvps->num > DTV_IOCTL_MAX_MSGS)
 		return -EINVAL;
 
 	tvp = memdup_user((void __user *)tvps->props, tvps->num * sizeof(*tvp));
 	if (IS_ERR(tvp))
 		return PTR_ERR(tvp);
 
+	/*
+	 * Let's use our own copy of property cache, in order to
+	 * avoid mangling with DTV zigzag logic, as drivers might
+	 * return crap, if they don't check if the data is available
+	 * before updating the properties cache.
+	 */
+	if (fepriv->state != FESTATE_IDLE) {
+		err = dtv_get_frontend(fe, &getp, NULL);
+		if (err < 0)
+			goto out;
+	}
 	for (i = 0; i < tvps->num; i++) {
-			err = dtv_property_process_set(fe, file,
-						       (tvp + i)->cmd,
-						       (tvp + i)->u.data);
-			if (err < 0) {
-				kfree(tvp);
-				return err;
+		err = dtv_property_process_get(fe, &getp,
+					       tvp + i, file);
+		if (err < 0)
+			goto out;
 	}
+
+	if (copy_to_user((void __user *)tvps->props, tvp,
+			 tvps->num * sizeof(struct dtv_property))) {
+		err = -EFAULT;
+		goto out;
 	}
-		kfree(tvp);
+
 	err = 0;
-		break;
-	}
-	case FE_GET_PROPERTY: {
+out:
+	kfree(tvp);
+	return err;
+}
+
+static int dvb_get_frontend(struct dvb_frontend *fe,
+			    struct dvb_frontend_parameters *p_out)
+{
+	struct dtv_frontend_properties getp;
+
+	/*
+	 * Let's use our own copy of property cache, in order to
+	 * avoid mangling with DTV zigzag logic, as drivers might
+	 * return crap, if they don't check if the data is available
+	 * before updating the properties cache.
+	 */
+	memcpy(&getp, &fe->dtv_property_cache, sizeof(getp));
+
+	return dtv_get_frontend(fe, &getp, p_out);
+}
+
+static int dvb_frontend_handle_ioctl(struct file *file,
+				     unsigned int cmd, void *parg)
+{
+	struct dvb_device *dvbdev = file->private_data;
+	struct dvb_frontend *fe = dvbdev->priv;
+	struct dvb_frontend_private *fepriv = fe->frontend_priv;
+	struct dtv_frontend_properties *c = &fe->dtv_property_cache;
+	int i, err = -ENOTSUPP;
+
+	dev_dbg(fe->dvb->device, "%s:\n", __func__);
+
+	switch (cmd) {
+	case FE_SET_PROPERTY: {
 		struct dtv_properties *tvps = parg;
 		struct dtv_property *tvp = NULL;
-		struct dtv_frontend_properties getp = fe->dtv_property_cache;
 
 		dev_dbg(fe->dvb->device, "%s: properties.num = %d\n",
 			__func__, tvps->num);
@@ -2377,37 +2415,22 @@ static int dvb_frontend_handle_ioctl(struct file *file,
 		if (IS_ERR(tvp))
 			return PTR_ERR(tvp);
 
-		/*
-		 * Let's use our own copy of property cache, in order to
-		 * avoid mangling with DTV zigzag logic, as drivers might
-		 * return crap, if they don't check if the data is available
-		 * before updating the properties cache.
-		 */
-		if (fepriv->state != FESTATE_IDLE) {
-			err = dtv_get_frontend(fe, &getp, NULL);
-			if (err < 0) {
-				kfree(tvp);
-				return err;
-			}
-		}
 		for (i = 0; i < tvps->num; i++) {
-			err = dtv_property_process_get(fe, &getp,
-						       tvp + i, file);
+			err = dtv_property_process_set(fe, file,
+						       (tvp + i)->cmd,
+						       (tvp + i)->u.data);
 			if (err < 0) {
 				kfree(tvp);
 				return err;
 			}
 		}
-
-		if (copy_to_user((void __user *)tvps->props, tvp,
-				 tvps->num * sizeof(struct dtv_property))) {
-			kfree(tvp);
-			return -EFAULT;
-		}
 		kfree(tvp);
 		err = 0;
 		break;
 	}
+	case FE_GET_PROPERTY:
+		err = dvb_get_property(fe, file, parg);
+		break;
 
 	case FE_GET_INFO: {
 		struct dvb_frontend_info *info = parg;
@@ -2545,7 +2568,6 @@ static int dvb_frontend_handle_ioctl(struct file *file,
 		fepriv->tune_mode_flags = (unsigned long)parg;
 		err = 0;
 		break;
-
 	/* DEPRECATED dish control ioctls */
 
 	case FE_DISHNETWORK_SEND_LEGACY_CMD:
@@ -2664,22 +2686,14 @@ static int dvb_frontend_handle_ioctl(struct file *file,
 			break;
 		err = dtv_set_frontend(fe);
 		break;
+
 	case FE_GET_EVENT:
 		err = dvb_frontend_get_event(fe, parg, file->f_flags);
 		break;
 
-	case FE_GET_FRONTEND: {
-		struct dtv_frontend_properties getp = fe->dtv_property_cache;
-
-		/*
-		 * Let's use our own copy of property cache, in order to
-		 * avoid mangling with DTV zigzag logic, as drivers might
-		 * return crap, if they don't check if the data is available
-		 * before updating the properties cache.
-		 */
-		err = dtv_get_frontend(fe, &getp, parg);
+	case FE_GET_FRONTEND:
+		err = dvb_get_frontend(fe, parg);
 		break;
-	}
 
 	default:
 		return -ENOTSUPP;