usb: gadget: uvc: Add struct for color matching in configs

Color matching descriptors are meant to be a per-format piece of data
and we need to be able to support different descriptors for different
formats. As a preliminary step towards that goal, switch the default
color matching configfs functionality to point to an instance of a
new struct uvcg_color_matching. Use the same default values for its
attributes as the currently hard-coded ones so that the interface to
userspace is consistent.
Reviewed-by: Laurent Pinchart <laurent.pinchart@ideasonboard.com>
Signed-off-by: Daniel Scally <dan.scally@ideasonboard.com>
Link: https://lore.kernel.org/r/20230202114142.300858-3-dan.scally@ideasonboard.comSigned-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

drivers/usb/gadget/function/uvc_configfs.c

@@ -13,6 +13,7 @@
 #include "uvc_configfs.h"
 
 #include <linux/sort.h>
+#include <linux/usb/video.h>
 
 /* -----------------------------------------------------------------------------
  * Global Utility Structures and Macros
@@ -1841,20 +1842,21 @@ static ssize_t uvcg_color_matching_##cname##_show(			\
 	struct config_item *item, char *page)				\
 {									\
 	struct config_group *group = to_config_group(item);		\
+	struct uvcg_color_matching *color_match =			\
+		to_uvcg_color_matching(group);				\
 	struct f_uvc_opts *opts;					\
 	struct config_item *opts_item;					\
 	struct mutex *su_mutex = &group->cg_subsys->su_mutex;		\
-	struct uvc_color_matching_descriptor *cd;			\
 	int result;							\
 									\
 	mutex_lock(su_mutex); /* for navigating configfs hierarchy */	\
 									\
 	opts_item = group->cg_item.ci_parent->ci_parent->ci_parent;	\
 	opts = to_f_uvc_opts(opts_item);				\
-	cd = &opts->uvc_color_matching;					\
 									\
 	mutex_lock(&opts->lock);					\
-	result = sprintf(page, "%u\n", le##bits##_to_cpu(cd->aname));	\
+	result = sprintf(page, "%u\n",					\
+			 le##bits##_to_cpu(color_match->desc.aname));	\
 	mutex_unlock(&opts->lock);					\
 									\
 	mutex_unlock(su_mutex);						\
@@ -1876,29 +1878,57 @@ static struct configfs_attribute *uvcg_color_matching_attrs[] = {
 	NULL,
 };
 
-static const struct uvcg_config_group_type uvcg_color_matching_type = {
-	.type = {
-		.ct_item_ops	= &uvcg_config_item_ops,
-		.ct_attrs	= uvcg_color_matching_attrs,
-		.ct_owner	= THIS_MODULE,
-	},
-	.name = "default",
+static void uvcg_color_matching_release(struct config_item *item)
+{
+	struct uvcg_color_matching *color_match =
+		to_uvcg_color_matching(to_config_group(item));
+
+	kfree(color_match);
+}
+
+static struct configfs_item_operations uvcg_color_matching_item_ops = {
+	.release	= uvcg_color_matching_release,
+};
+
+static const struct config_item_type uvcg_color_matching_type = {
+	.ct_item_ops	= &uvcg_color_matching_item_ops,
+	.ct_attrs	= uvcg_color_matching_attrs,
+	.ct_owner	= THIS_MODULE,
 };
 
 /* -----------------------------------------------------------------------------
  * streaming/color_matching
  */
 
+static int uvcg_color_matching_create_children(struct config_group *parent)
+{
+	struct uvcg_color_matching *color_match;
+
+	color_match = kzalloc(sizeof(*color_match), GFP_KERNEL);
+	if (!color_match)
+		return -ENOMEM;
+
+	color_match->desc.bLength = UVC_DT_COLOR_MATCHING_SIZE;
+	color_match->desc.bDescriptorType = USB_DT_CS_INTERFACE;
+	color_match->desc.bDescriptorSubType = UVC_VS_COLORFORMAT;
+	color_match->desc.bColorPrimaries = UVC_COLOR_PRIMARIES_BT_709_SRGB;
+	color_match->desc.bTransferCharacteristics = UVC_TRANSFER_CHARACTERISTICS_BT_709;
+	color_match->desc.bMatrixCoefficients = UVC_MATRIX_COEFFICIENTS_SMPTE_170M;
+
+	config_group_init_type_name(&color_match->group, "default",
+				    &uvcg_color_matching_type);
+	configfs_add_default_group(&color_match->group, parent);
+
+	return 0;
+}
+
 static const struct uvcg_config_group_type uvcg_color_matching_grp_type = {
 	.type = {
 		.ct_item_ops	= &uvcg_config_item_ops,
 		.ct_owner	= THIS_MODULE,
 	},
 	.name = "color_matching",
-	.children = (const struct uvcg_config_group_type*[]) {
-		&uvcg_color_matching_type,
-		NULL,
-	},
+	.create_children = uvcg_color_matching_create_children,
 };
 
 /* -----------------------------------------------------------------------------

drivers/usb/gadget/function/uvc_configfs.h

@@ -37,6 +37,14 @@ static inline struct uvcg_control_header *to_uvcg_control_header(struct config_i
 	return container_of(item, struct uvcg_control_header, item);
 }
 
+struct uvcg_color_matching {
+	struct config_group group;
+	struct uvc_color_matching_descriptor desc;
+};
+
+#define to_uvcg_color_matching(group_ptr) \
+container_of(group_ptr, struct uvcg_color_matching, group)
+
 enum uvcg_format_type {
 	UVCG_UNCOMPRESSED = 0,
 	UVCG_MJPEG,