[PATCH] media: uvcvideo: Use indexed loops in uvc_ctrl_init_ctrl()

[Laurent Pinchart <laurent.pinchart@xxxxxxxxxxxxxxxx>]

As shown by the bug introduced in commit 86f7ef773156 ("media: uvcvideo:
Add support for per-device control mapping overrides"), the loop style
used by uvc_ctrl_init_ctrl() is error-prone. Rewrite the loops to use
indices instead.

Signed-off-by: Laurent Pinchart <laurent.pinchart@xxxxxxxxxxxxxxxx>
---
This patch depends on https://lore.kernel.org/linux-media/20220718121219.16079-1-laurent.pinchart@xxxxxxxxxxxxxxxx
---
 drivers/media/usb/uvc/uvc_ctrl.c | 34 ++++++++++++++++++--------------
 1 file changed, 19 insertions(+), 15 deletions(-)

diff --git a/drivers/media/usb/uvc/uvc_ctrl.c b/drivers/media/usb/uvc/uvc_ctrl.c
index 8c208db9600b..5c33b0b7ef9a 100644
--- a/drivers/media/usb/uvc/uvc_ctrl.c
+++ b/drivers/media/usb/uvc/uvc_ctrl.c
@@ -2411,10 +2411,9 @@ static void uvc_ctrl_prune_entity(struct uvc_device *dev,
 static void uvc_ctrl_init_ctrl(struct uvc_video_chain *chain,
 			       struct uvc_control *ctrl)
 {
-	const struct uvc_control_info *info = uvc_ctrls;
-	const struct uvc_control_info *iend = info + ARRAY_SIZE(uvc_ctrls);
-	const struct uvc_control_mapping *mapping;
-	const struct uvc_control_mapping *mend;
+	const struct uvc_control_mapping *mappings;
+	unsigned int num_mappings;
+	unsigned int i;
 
 	/*
 	 * XU controls initialization requires querying the device for control
@@ -2425,7 +2424,9 @@ static void uvc_ctrl_init_ctrl(struct uvc_video_chain *chain,
 	if (UVC_ENTITY_TYPE(ctrl->entity) == UVC_VC_EXTENSION_UNIT)
 		return;
 
-	for (; info < iend; ++info) {
+	for (i = 0; i < ARRAY_SIZE(uvc_ctrls); ++i) {
+		const struct uvc_control_info *info = &uvc_ctrls[i];
+
 		if (uvc_entity_match_guid(ctrl->entity, info->entity) &&
 		    ctrl->index == info->index) {
 			uvc_ctrl_add_info(chain->dev, ctrl, info);
@@ -2452,9 +2453,11 @@ static void uvc_ctrl_init_ctrl(struct uvc_video_chain *chain,
 	 */
 	if (chain->dev->info->mappings) {
 		bool custom = false;
-		unsigned int i;
 
-		for (i = 0; (mapping = chain->dev->info->mappings[i]); ++i) {
+		for (i = 0; chain->dev->info->mappings[i]; ++i) {
+			const struct uvc_control_mapping *mapping =
+				chain->dev->info->mappings[i];
+
 			if (uvc_entity_match_guid(ctrl->entity, mapping->entity) &&
 			    ctrl->info.selector == mapping->selector) {
 				__uvc_ctrl_add_mapping(chain, ctrl, mapping);
@@ -2467,10 +2470,9 @@ static void uvc_ctrl_init_ctrl(struct uvc_video_chain *chain,
 	}
 
 	/* Process common mappings next. */
-	mapping = uvc_ctrl_mappings;
-	mend = mapping + ARRAY_SIZE(uvc_ctrl_mappings);
+	for (i = 0; i < ARRAY_SIZE(uvc_ctrl_mappings); ++i) {
+		const struct uvc_control_mapping *mapping = &uvc_ctrl_mappings[i];
 
-	for (; mapping < mend; ++mapping) {
 		if (uvc_entity_match_guid(ctrl->entity, mapping->entity) &&
 		    ctrl->info.selector == mapping->selector)
 			__uvc_ctrl_add_mapping(chain, ctrl, mapping);
@@ -2478,14 +2480,16 @@ static void uvc_ctrl_init_ctrl(struct uvc_video_chain *chain,
 
 	/* Finally process version-specific mappings. */
 	if (chain->dev->uvc_version < 0x0150) {
-		mapping = uvc_ctrl_mappings_uvc11;
-		mend = mapping + ARRAY_SIZE(uvc_ctrl_mappings_uvc11);
+		mappings = uvc_ctrl_mappings_uvc11;
+		num_mappings = ARRAY_SIZE(uvc_ctrl_mappings_uvc11);
 	} else {
-		mapping = uvc_ctrl_mappings_uvc15;
-		mend = mapping + ARRAY_SIZE(uvc_ctrl_mappings_uvc15);
+		mappings = uvc_ctrl_mappings_uvc15;
+		num_mappings = ARRAY_SIZE(uvc_ctrl_mappings_uvc15);
 	}
 
-	for (; mapping < mend; ++mapping) {
+	for (i = 0; i < num_mappings; ++i) {
+		const struct uvc_control_mapping *mapping = &mappings[i];
+
 		if (uvc_entity_match_guid(ctrl->entity, mapping->entity) &&
 		    ctrl->info.selector == mapping->selector)
 			__uvc_ctrl_add_mapping(chain, ctrl, mapping);
-- 
Regards,

Laurent Pinchart