[PATCH 6/6] usb: gadget: uvc: Allow creating new color matching descriptors

[Daniel Scally <dan.scally@ideasonboard.com>]

Allow users to create new color matching descriptors in addition to
the default one. These must be associated with a UVC format in order
to be transmitted to the host, which is achieved by symlinking from
the format to the newly created color matching descriptor - extend
the uncompressed and mjpeg formats to support that linking operation.

Signed-off-by: Daniel Scally <dan.scally@ideasonboard.com>
---
 .../ABI/testing/configfs-usb-gadget-uvc       |  4 +-
 drivers/usb/gadget/function/uvc_configfs.c    | 79 ++++++++++++++++++-
 2 files changed, 79 insertions(+), 4 deletions(-)

diff --git a/Documentation/ABI/testing/configfs-usb-gadget-uvc b/Documentation/ABI/testing/configfs-usb-gadget-uvc
index 3512f4899fe3..ce629f0880a9 100644
--- a/Documentation/ABI/testing/configfs-usb-gadget-uvc
+++ b/Documentation/ABI/testing/configfs-usb-gadget-uvc
@@ -160,10 +160,10 @@ Date:		Dec 2014
 KernelVersion:	4.0
 Description:	Color matching descriptors
 
-What:		/config/usb-gadget/gadget/functions/uvc.name/streaming/color_matching/default
+What:		/config/usb-gadget/gadget/functions/uvc.name/streaming/color_matching/name
 Date:		Dec 2014
 KernelVersion:	4.0
-Description:	Default color matching descriptors
+Description:	color matching descriptors
 
 		All attributes read/write:
 
diff --git a/drivers/usb/gadget/function/uvc_configfs.c b/drivers/usb/gadget/function/uvc_configfs.c
index 4fbc42d738a4..82c10f0dab71 100644
--- a/drivers/usb/gadget/function/uvc_configfs.c
+++ b/drivers/usb/gadget/function/uvc_configfs.c
@@ -769,6 +769,58 @@ static struct uvcg_cmd *uvcg_format_get_default_cmd(struct config_item *streamin
 	return cmd;
 }
 
+static int uvcg_format_allow_link(struct config_item *src, struct config_item *tgt)
+{
+	struct mutex *su_mutex = &src->ci_group->cg_subsys->su_mutex;
+	struct config_item *streaming, *color_matching;
+	struct uvcg_cmd *color_matching_desc;
+	struct uvcg_format *fmt;
+	int ret = 0;
+
+	mutex_lock(su_mutex);
+
+	streaming = src->ci_parent->ci_parent;
+	color_matching = config_group_find_item(to_config_group(streaming), "color_matching");
+	if (!color_matching || color_matching != tgt->ci_parent) {
+		ret = -EINVAL;
+		goto out_put_cm;
+	}
+
+	color_matching_desc = to_uvcg_cmd(to_config_group(tgt));
+	fmt = to_uvcg_format(src);
+	fmt->color_matching = color_matching_desc;
+
+out_put_cm:
+	config_item_put(color_matching);
+	mutex_unlock(su_mutex);
+
+	return ret;
+}
+
+static void uvcg_format_drop_link(struct config_item *src, struct config_item *tgt)
+{
+	struct config_item *streaming;
+	struct mutex *su_mutex = &src->ci_group->cg_subsys->su_mutex;
+	struct uvcg_format *fmt;
+	struct uvcg_cmd *cmd;
+
+	mutex_lock(su_mutex);
+
+	streaming = src->ci_parent->ci_parent;
+	cmd = uvcg_format_get_default_cmd(streaming);
+
+	fmt = to_uvcg_format(src);
+	fmt->color_matching = cmd;
+
+	mutex_unlock(su_mutex);
+}
+
+static struct configfs_item_operations uvcg_format_item_operations = {
+	.release	= uvcg_config_item_release,
+	.allow_link	= uvcg_format_allow_link,
+	.drop_link	= uvcg_format_drop_link,
+};
+
 static ssize_t uvcg_format_bma_controls_show(struct uvcg_format *f, char *page)
 {
 	struct f_uvc_opts *opts;
@@ -1569,7 +1621,7 @@ static struct configfs_attribute *uvcg_uncompressed_attrs[] = {
 };
 
 static const struct config_item_type uvcg_uncompressed_type = {
-	.ct_item_ops	= &uvcg_config_item_ops,
+	.ct_item_ops	= &uvcg_format_item_operations,
 	.ct_group_ops	= &uvcg_uncompressed_group_ops,
 	.ct_attrs	= uvcg_uncompressed_attrs,
 	.ct_owner	= THIS_MODULE,
@@ -1764,7 +1816,7 @@ static struct configfs_attribute *uvcg_mjpeg_attrs[] = {
 };
 
 static const struct config_item_type uvcg_mjpeg_type = {
-	.ct_item_ops	= &uvcg_config_item_ops,
+	.ct_item_ops	= &uvcg_format_item_operations,
 	.ct_group_ops	= &uvcg_mjpeg_group_ops,
 	.ct_attrs	= uvcg_mjpeg_attrs,
 	.ct_owner	= THIS_MODULE,
@@ -1912,6 +1964,28 @@ static const struct config_item_type uvcg_color_matching_type = {
  * streaming/color_matching
  */
 
+static struct config_group *uvcg_color_matching_make(struct config_group *group,
+						     const char *name)
+{
+	struct uvcg_cmd *cmd;
+
+	cmd = kzalloc(sizeof(*cmd), GFP_KERNEL);
+	if (!cmd)
+		return ERR_PTR(-ENOMEM);
+
+	cmd->desc.bLength = UVC_DT_COLOR_MATCHING_SIZE;
+	cmd->desc.bDescriptorType = USB_DT_CS_INTERFACE;
+	cmd->desc.bDescriptorSubType = UVC_VS_COLORFORMAT;
+
+	config_group_init_type_name(&cmd->group, name, &uvcg_color_matching_type);
+
+	return &cmd->group;
+}
+
+static struct configfs_group_operations uvcg_color_matching_grp_group_ops = {
+	.make_group	= uvcg_color_matching_make,
+};
+
 static int uvcg_color_matching_create_children(struct config_group *parent)
 {
 	struct uvcg_cmd *cmd;
@@ -1937,6 +2011,7 @@ static int uvcg_color_matching_create_children(struct config_group *parent)
 static const struct uvcg_config_group_type uvcg_color_matching_grp_type = {
 	.type = {
 		.ct_item_ops	= &uvcg_config_item_ops,
+		.ct_group_ops	= &uvcg_color_matching_grp_group_ops,
 		.ct_owner	= THIS_MODULE,
 	},
 	.name = "color_matching",
-- 
2.34.1