usb: gadget: uvc: configfs: Add interface number attributes

The video control and video streaming interface numbers are needed in
the UVC gadget userspace stack to reply to UVC requests. They are
hardcoded to fixed values at the moment, preventing configurations with
multiple functions.

To fix this, make them dynamically discoverable by userspace through
read-only configfs attributes in <function>/control/bInterfaceNumber and
<function>/streaming/bInterfaceNumber respectively.

Signed-off-by: Laurent Pinchart <laurent.pinchart@ideasonboard.com>
Reviewed-by: Kieran Bingham <kieran.bingham@ideasonboard.com>

3 files changed, 67 insertions, 0 deletions

diff --git a/drivers/usb/gadget/function/f_uvc.c b/drivers/usb/gadget/function/f_uvc.c
index 95cb1b5f5ffe..4ea987741e6e 100644
--- a/drivers/usb/gadget/function/f_uvc.c
+++ b/drivers/usb/gadget/function/f_uvc.c
@@ -699,12 +699,14 @@ uvc_function_bind(struct usb_configuration *c, struct usb_function *f)
 	uvc_iad.bFirstInterface = ret;
 	uvc_control_intf.bInterfaceNumber = ret;
 	uvc->control_intf = ret;
+	opts->control_interface = ret;
 
 	if ((ret = usb_interface_id(c, f)) < 0)
 		goto error;
 	uvc_streaming_intf_alt0.bInterfaceNumber = ret;
 	uvc_streaming_intf_alt1.bInterfaceNumber = ret;
 	uvc->streaming_intf = ret;
+	opts->streaming_interface = ret;
 
 	/* Copy descriptors */
 	f->fs_descriptors = uvc_copy_descriptors(uvc, USB_SPEED_FULL);
diff --git a/drivers/usb/gadget/function/u_uvc.h b/drivers/usb/gadget/function/u_uvc.h
index 2ed292e94fbc..5242d489e20a 100644
--- a/drivers/usb/gadget/function/u_uvc.h
+++ b/drivers/usb/gadget/function/u_uvc.h
@@ -25,6 +25,9 @@ struct f_uvc_opts {
 	unsigned int					streaming_maxpacket;
 	unsigned int					streaming_maxburst;
 
+	unsigned int					control_interface;
+	unsigned int					streaming_interface;
+
 	/*
 	 * Control descriptors array pointers for full-/high-speed and
 	 * super-speed. They point by default to the uvc_fs_control_cls and
diff --git a/drivers/usb/gadget/function/uvc_configfs.c b/drivers/usb/gadget/function/uvc_configfs.c
index ae722549eabc..fa8d2e1f54ba 100644
--- a/drivers/usb/gadget/function/uvc_configfs.c
+++ b/drivers/usb/gadget/function/uvc_configfs.c
@@ -713,9 +713,40 @@ static const struct uvcg_config_group_type uvcg_control_class_grp_type = {
  * control
  */
 
+static ssize_t uvcg_default_control_b_interface_number_show(
+	struct config_item *item, char *page)
+{
+	struct config_group *group = to_config_group(item);
+	struct mutex *su_mutex = &group->cg_subsys->su_mutex;
+	struct config_item *opts_item;
+	struct f_uvc_opts *opts;
+	int result = 0;
+
+	mutex_lock(su_mutex); /* for navigating configfs hierarchy */
+
+	opts_item = item->ci_parent;
+	opts = to_f_uvc_opts(opts_item);
+
+	mutex_lock(&opts->lock);
+	result += sprintf(page, "%u\n", opts->control_interface);
+	mutex_unlock(&opts->lock);
+
+	mutex_unlock(su_mutex);
+
+	return result;
+}
+
+UVC_ATTR_RO(uvcg_default_control_, b_interface_number, bInterfaceNumber);
+
+static struct configfs_attribute *uvcg_default_control_attrs[] = {
+	&uvcg_default_control_attr_b_interface_number,
+	NULL,
+};
+
 static const struct uvcg_config_group_type uvcg_control_grp_type = {
 	.type = {
 		.ct_item_ops	= &uvcg_config_item_ops,
+		.ct_attrs	= uvcg_default_control_attrs,
 		.ct_owner	= THIS_MODULE,
 	},
 	.name = "control",
@@ -2259,9 +2290,40 @@ static const struct uvcg_config_group_type uvcg_streaming_class_grp_type = {
  * streaming
  */
 
+static ssize_t uvcg_default_streaming_b_interface_number_show(
+	struct config_item *item, char *page)
+{
+	struct config_group *group = to_config_group(item);
+	struct mutex *su_mutex = &group->cg_subsys->su_mutex;
+	struct config_item *opts_item;
+	struct f_uvc_opts *opts;
+	int result = 0;
+
+	mutex_lock(su_mutex); /* for navigating configfs hierarchy */
+
+	opts_item = item->ci_parent;
+	opts = to_f_uvc_opts(opts_item);
+
+	mutex_lock(&opts->lock);
+	result += sprintf(page, "%u\n", opts->streaming_interface);
+	mutex_unlock(&opts->lock);
+
+	mutex_unlock(su_mutex);
+
+	return result;
+}
+
+UVC_ATTR_RO(uvcg_default_streaming_, b_interface_number, bInterfaceNumber);
+
+static struct configfs_attribute *uvcg_default_streaming_attrs[] = {
+	&uvcg_default_streaming_attr_b_interface_number,
+	NULL,
+};
+
 static const struct uvcg_config_group_type uvcg_streaming_grp_type = {
 	.type = {
 		.ct_item_ops	= &uvcg_config_item_ops,
+		.ct_attrs	= uvcg_default_streaming_attrs,
 		.ct_owner	= THIS_MODULE,
 	},
 	.name = "streaming",