usb: gadget: uvc: track frames in format entries

Just like the header is tracking the formats in a linked list, in this
patch we track the frames in a linked list of the formats. It
simplifies the parsing of the configfs structure.

Signed-off-by: Michael Grzeschik <m.grzeschik@pengutronix.de>

Link: https://lore.kernel.org/r/20220421211427.3400834-6-m.grzeschik@pengutronix.de
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

drivers/usb/gadget/function/uvc_configfs.c

@@ -1262,6 +1262,7 @@ static struct config_item *uvcg_frame_make(struct config_group *group,
 	struct uvcg_format *fmt;
 	struct f_uvc_opts *opts;
 	struct config_item *opts_item;
+	struct uvcg_frame_ptr *frame_ptr;
 
 	h = kzalloc(sizeof(*h), GFP_KERNEL);
 	if (!h)
@@ -1292,6 +1293,16 @@ static struct config_item *uvcg_frame_make(struct config_group *group,
 		kfree(h);
 		return ERR_PTR(-EINVAL);
 	}
+
+	frame_ptr = kzalloc(sizeof(*frame_ptr), GFP_KERNEL);
+	if (!frame_ptr) {
+		mutex_unlock(&opts->lock);
+		kfree(h);
+		return ERR_PTR(-ENOMEM);
+	}
+
+	frame_ptr->frm = h;
+	list_add_tail(&frame_ptr->entry, &fmt->frames);
 	++fmt->num_frames;
 	mutex_unlock(&opts->lock);
 
@@ -1305,13 +1316,23 @@ static void uvcg_frame_drop(struct config_group *group, struct config_item *item
 	struct uvcg_format *fmt;
 	struct f_uvc_opts *opts;
 	struct config_item *opts_item;
+	struct uvcg_frame *target_frm = NULL;
+	struct uvcg_frame_ptr *frame_ptr, *tmp;
 
 	opts_item = group->cg_item.ci_parent->ci_parent->ci_parent;
 	opts = to_f_uvc_opts(opts_item);
 
 	mutex_lock(&opts->lock);
+	target_frm = container_of(item, struct uvcg_frame, item);
 	fmt = to_uvcg_format(&group->cg_item);
-	--fmt->num_frames;
+
+	list_for_each_entry_safe(frame_ptr, tmp, &fmt->frames, entry)
+		if (frame_ptr->frm == target_frm) {
+			list_del(&frame_ptr->entry);
+			kfree(frame_ptr);
+			--fmt->num_frames;
+			break;
+		}
 	mutex_unlock(&opts->lock);
 
 	config_item_put(item);
@@ -1556,6 +1577,7 @@ static struct config_group *uvcg_uncompressed_make(struct config_group *group,
 	h->desc.bmInterfaceFlags	= 0;
 	h->desc.bCopyProtect		= 0;
 
+	INIT_LIST_HEAD(&h->fmt.frames);
 	h->fmt.type = UVCG_UNCOMPRESSED;
 	config_group_init_type_name(&h->fmt.group, name,
 				    &uvcg_uncompressed_type);
@@ -1736,6 +1758,7 @@ static struct config_group *uvcg_mjpeg_make(struct config_group *group,
 	h->desc.bmInterfaceFlags	= 0;
 	h->desc.bCopyProtect		= 0;
 
+	INIT_LIST_HEAD(&h->fmt.frames);
 	h->fmt.type = UVCG_MJPEG;
 	config_group_init_type_name(&h->fmt.group, name,
 				    &uvcg_mjpeg_type);

drivers/usb/gadget/function/uvc_configfs.h

@@ -46,6 +46,7 @@ struct uvcg_format {
 	struct config_group	group;
 	enum uvcg_format_type	type;
 	unsigned		linked;
+	struct list_head	frames;
 	unsigned		num_frames;
 	__u8			bmaControls[UVCG_STREAMING_CONTROL_SIZE];
 };
@@ -73,6 +74,11 @@ static inline struct uvcg_streaming_header *to_uvcg_streaming_header(struct conf
 	return container_of(item, struct uvcg_streaming_header, item);
 }
 
+struct uvcg_frame_ptr {
+	struct uvcg_frame	*frm;
+	struct list_head	entry;
+};
+
 struct uvcg_frame {
 	struct config_item	item;
 	enum uvcg_format_type	fmt_type;