configfs: Refactor ConfigFS parsing code

Move all attribute parsing to a top-level configfs_parse_uvc() function,
and split control and streaming interface attributes to two separate
helper functions. In addition to making the code more structured, it
will also allow supporting multiple streaming interfaces in a single UVC
function in the future.

The uvc_function_config structure is similarly reorganized in a
hierarchical representation of the configuration.

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

3 files changed, 128 insertions, 37 deletions

diff --git a/configfs.c b/configfs.c
index 3b98f55..38954d5 100644
--- a/configfs.c
+++ b/configfs.c
@@ -199,12 +199,21 @@ static char *udc_find_video_device(const char *udc, const char *function)
  */
 
 static const struct uvc_function_config g_webcam_config = {
-	.control_interface = 0,
-	.streaming_interface = 1,
-
-	.streaming_interval = 1,
-	.streaming_maxburst = 0,
-	.streaming_maxpacket = 1024,
+	.control = {
+		.intf = {
+			.bInterfaceNumber = 0,
+		},
+	},
+	.streaming = {
+		.intf = {
+			.bInterfaceNumber = 1,
+		},
+		.ep = {
+			.bInterval = 1,
+			.bMaxBurst = 0,
+			.wMaxPacketSize = 1024,
+		},
+	},
 };
 
 static int parse_legacy_g_webcam(const char *udc,
@@ -269,16 +278,74 @@ void configfs_free_uvc_function(struct uvc_function_config *fc)
 	free(fc);
 }
 
-static int configfs_parse_interfaces(const char *fpath,
-				     struct uvc_function_config *fc)
+#define configfs_parse_child(parent, child, cfg, parse)			\
+({									\
+	char *__path;							\
+	int __ret;							\
+									\
+	__path = path_join((parent), (child));				\
+	if (__path) {							\
+		__ret = parse(__path, (cfg));				\
+		free(__path);						\
+	} else {							\
+		__ret = -ENOMEM;					\
+	}								\
+									\
+	__ret;								\
+})
+
+static int configfs_parse_interface(const char *path,
+				    struct uvc_function_config_interface *cfg)
 {
 	int ret;
 
-	ret = attribute_read_uint(fpath, "control/bInterfaceNumber",
-				  &fc->control_interface);
+	ret = attribute_read_uint(path, "bInterfaceNumber",
+				  &cfg->bInterfaceNumber);
+
+	return ret;
+}
+
+static int configfs_parse_control(const char *path,
+				  struct uvc_function_config_control *cfg)
+{
+	int ret;
+
+	ret = configfs_parse_interface(path, &cfg->intf);
+
+	return ret;
+}
+
+static int configfs_parse_streaming(const char *path,
+				    struct uvc_function_config_streaming *cfg)
+{
+	int ret;
+
+	ret = configfs_parse_interface(path, &cfg->intf);
+
+	return ret;
+}
+
+static int configfs_parse_uvc(const char *fpath,
+			      struct uvc_function_config *fc)
+{
+	int ret = 0;
 
-	ret = ret ? : attribute_read_uint(fpath, "streaming/bInterfaceNumber",
-					  &fc->streaming_interface);
+	ret = ret ? : configfs_parse_child(fpath, "control", &fc->control,
+					   configfs_parse_control);
+	ret = ret ? : configfs_parse_child(fpath, "streaming", &fc->streaming,
+					   configfs_parse_streaming);
+
+	/*
+	 * These parameters should be part of the streaming interface in
+	 * ConfigFS, but for legacy reasons they are located directly in the
+	 * function directory.
+	 */
+	ret = ret ? : attribute_read_uint(fpath, "streaming_interval",
+					  &fc->streaming.ep.bInterval);
+	ret = ret ? : attribute_read_uint(fpath, "streaming_maxburst",
+					  &fc->streaming.ep.bMaxBurst);
+	ret = ret ? : attribute_read_uint(fpath, "streaming_maxpacket",
+					  &fc->streaming.ep.wMaxPacketSize);
 
 	return ret;
 }
@@ -337,21 +404,14 @@ struct uvc_function_config *configfs_parse_uvc_function(const char *function)
 
 	fc->udc = attribute_read_str(fpath, "../../UDC");
 	fc->video = udc_find_video_device(fc->udc, function);
-	if (!fc->video)
+	if (!fc->video) {
 		ret = -ENODEV;
+		goto done;
+	}
 
-	/* Identify interface numbers. */
-	ret = ret ? : configfs_parse_interfaces(fpath, fc);
-
-	ret = ret ? : attribute_read_uint(fpath, "streaming_interval",
-					  &fc->streaming_interval);
-
-	ret = ret ? : attribute_read_uint(fpath, "streaming_maxburst",
-					  &fc->streaming_maxburst);
-
-	ret = ret ? : attribute_read_uint(fpath, "streaming_maxpacket",
-					  &fc->streaming_maxpacket);
+	ret = configfs_parse_uvc(fpath, fc);
 
+done:
 	if (ret) {
 		configfs_free_uvc_function(fc);
 		fc = NULL;
diff --git a/configfs.h b/configfs.h
index b5c7480..9f7f377 100644
--- a/configfs.h
+++ b/configfs.h
@@ -11,25 +11,56 @@
 #define __CONFIGFS_H__
 
 /*
+ * struct uvc_function_config_endpoint - Endpoint parameters
+ * @bInterval: Transfer interval (interrupt and isochronous only)
+ * @bMaxBurst: Transfer burst size (super-speed only)
+ * @wMaxPacketSize: Maximum packet size (including the multiplier)
+ */
+struct uvc_function_config_endpoint {
+	unsigned int bInterval;
+	unsigned int bMaxBurst;
+	unsigned int wMaxPacketSize;
+};
+
+/*
+ * struct uvc_function_config_interface - Interface parameters
+ * @bInterfaceNumber: Interface number
+ */
+struct uvc_function_config_interface {
+	unsigned int bInterfaceNumber;
+};
+
+/*
+ * struct uvc_function_config_control - Control interface parameters
+ * @intf: Generic interface parameters
+ */
+struct uvc_function_config_control {
+	struct uvc_function_config_interface intf;
+};
+
+/*
+ * struct uvc_function_config_streaming - Streaming interface parameters
+ * @intf: Generic interface parameters
+ * @ep: Endpoint parameters
+ */
+struct uvc_function_config_streaming {
+	struct uvc_function_config_interface intf;
+	struct uvc_function_config_endpoint ep;
+};
+
+/*
  * struct uvc_function_config - UVC function configuration parameters
  * @video: Full path to the video device node
  * @udc: UDC name
- * @control_interface: Control interface number
- * @streaming_interface: Streaming interface number
- * @streaming_interval: Isochronous interval for the streaming endpoint
- * @streaming_maxburts: Isochronous maximum burst for the streaming endpoint
- * @streaming_maxpacket: Isochronous maximum packets for the streaming endpoint
+ * @control: Control interface configuration
+ * @streaming: Streaming interface configuration
  */
 struct uvc_function_config {
 	char *video;
 	char *udc;
 
-	unsigned int control_interface;
-	unsigned int streaming_interface;
-
-	unsigned int streaming_interval;
-	unsigned int streaming_maxburst;
-	unsigned int streaming_maxpacket;
+	struct uvc_function_config_control control;
+	struct uvc_function_config_streaming streaming;
 };
 
 struct uvc_function_config *configfs_parse_uvc_function(const char *function);
diff --git a/uvc-gadget.c b/uvc-gadget.c
index 96f9996..57dc097 100644
--- a/uvc-gadget.c
+++ b/uvc-gadget.c
@@ -414,9 +414,9 @@ uvc_events_process_class(struct uvc_device *dev,
 	if ((ctrl->bRequestType & USB_RECIP_MASK) != USB_RECIP_INTERFACE)
 		return;
 
-	if (interface == dev->fc->control_interface)
+	if (interface == dev->fc->control.intf.bInterfaceNumber)
 		uvc_events_process_control(dev, ctrl->bRequest, ctrl->wValue >> 8, resp);
-	else if (interface == dev->fc->streaming_interface)
+	else if (interface == dev->fc->streaming.intf.bInterfaceNumber)
 		uvc_events_process_streaming(dev, ctrl->bRequest, ctrl->wValue >> 8, resp);
 }