usb: gadget: f_subset: add configfs support

f_subset learns about configfs so we can, eventually,
remove in-kernel gadget drivers.
Signed-off-by: Andrzej Pietrasiewicz <andrzej.p@samsung.com>
Signed-off-by: Kyungmin Park <kyungmin.park@samsung.com>
Signed-off-by: Felipe Balbi <balbi@ti.com>

Documentation/ABI/testing/configfs-usb-gadget-subset

+What:		/config/usb-gadget/gadget/functions/geth.name
+Date:		May 2013
+KenelVersion:	3.11
+Description:
+		The attributes:
+
+		ifname		- network device interface name associated with
+				this function instance
+		qmult		- queue length multiplier for high and
+				super speed
+		host_addr	- MAC address of host's end of this
+				Ethernet over USB link
+		dev_addr	- MAC address of device's end of this
+				Ethernet over USB link

drivers/usb/gadget/Kconfig

@@ -547,6 +547,16 @@ choice
 
 # this first set of drivers all depend on bulk-capable hardware.
 
+config USB_CONFIGFS_ECM_SUBSET
+	boolean "Ethernet Control Model (CDC ECM) subset"
+	depends on USB_CONFIGFS
+	depends on NET
+	select USB_U_ETHER
+	select USB_F_SUBSET
+	help
+	  On hardware that can't implement the full protocol,
+	  a simple CDC subset is used, placing fewer demands on USB.
+
 config USB_CONFIGFS_EEM
 	bool "Ethernet Emulation Model (EEM)"
 	depends on USB_CONFIGFS

drivers/usb/gadget/f_subset.c

@@ -17,6 +17,7 @@
 #include <linux/etherdevice.h>
 
 #include "u_ether.h"
+#include "u_ether_configfs.h"
 #include "u_gether.h"
 
 /*
@@ -313,8 +314,10 @@ geth_bind(struct usb_configuration *c, struct usb_function *f)
 	 * with regard to gether_opts->bound access
 	 */
 	if (!gether_opts->bound) {
+		mutex_lock(&gether_opts->lock);
 		gether_set_gadget(gether_opts->net, cdev->gadget);
 		status = gether_register_netdev(gether_opts->net);
+		mutex_unlock(&gether_opts->lock);
 		if (status)
 			return status;
 		gether_opts->bound = true;
@@ -445,6 +448,41 @@ int geth_bind_config(struct usb_configuration *c, u8 ethaddr[ETH_ALEN],
 
 #else
 
+static inline struct f_gether_opts *to_f_gether_opts(struct config_item *item)
+{
+	return container_of(to_config_group(item), struct f_gether_opts,
+			    func_inst.group);
+}
+
+/* f_gether_item_ops */
+USB_ETHERNET_CONFIGFS_ITEM(gether);
+
+/* f_gether_opts_dev_addr */
+USB_ETHERNET_CONFIGFS_ITEM_ATTR_DEV_ADDR(gether);
+
+/* f_gether_opts_host_addr */
+USB_ETHERNET_CONFIGFS_ITEM_ATTR_HOST_ADDR(gether);
+
+/* f_gether_opts_qmult */
+USB_ETHERNET_CONFIGFS_ITEM_ATTR_QMULT(gether);
+
+/* f_gether_opts_ifname */
+USB_ETHERNET_CONFIGFS_ITEM_ATTR_IFNAME(gether);
+
+static struct configfs_attribute *gether_attrs[] = {
+	&f_gether_opts_dev_addr.attr,
+	&f_gether_opts_host_addr.attr,
+	&f_gether_opts_qmult.attr,
+	&f_gether_opts_ifname.attr,
+	NULL,
+};
+
+static struct config_item_type gether_func_type = {
+	.ct_item_ops	= &gether_item_ops,
+	.ct_attrs	= gether_attrs,
+	.ct_owner	= THIS_MODULE,
+};
+
 static void geth_free_inst(struct usb_function_instance *f)
 {
 	struct f_gether_opts *opts;
@@ -464,12 +502,15 @@ static struct usb_function_instance *geth_alloc_inst(void)
 	opts = kzalloc(sizeof(*opts), GFP_KERNEL);
 	if (!opts)
 		return ERR_PTR(-ENOMEM);
-
+	mutex_init(&opts->lock);
 	opts->func_inst.free_func_inst = geth_free_inst;
 	opts->net = gether_setup_default();
 	if (IS_ERR(opts->net))
 		return ERR_CAST(opts->net);
 
+	config_group_init_type_name(&opts->func_inst.group, "",
+				    &gether_func_type);
+
 	return &opts->func_inst;
 }
 
@@ -500,6 +541,8 @@ static struct usb_function *geth_alloc(struct usb_function_instance *fi)
 
 	opts = container_of(fi, struct f_gether_opts, func_inst);
 
+	mutex_lock(&opts->lock);
+	opts->refcnt++;
 	/* export host's Ethernet address in CDC format */
 	status = gether_get_host_addr_cdc(opts->net, geth->ethaddr,
 					  sizeof(geth->ethaddr));
@@ -510,6 +553,7 @@ static struct usb_function *geth_alloc(struct usb_function_instance *fi)
 	geth_string_defs[1].s = geth->ethaddr;
 
 	geth->port.ioport = netdev_priv(opts->net);
+	mutex_unlock(&opts->lock);
 	geth->port.cdc_filter = DEFAULT_FILTER;
 
 	geth->port.func.name = "cdc_subset";

drivers/usb/gadget/u_gether.h

@@ -22,6 +22,15 @@ struct f_gether_opts {
 	struct usb_function_instance	func_inst;
 	struct net_device		*net;
 	bool				bound;
+
+	/*
+	 * Read/write access to configfs attributes is handled by configfs.
+	 *
+	 * This is to protect the data from concurrent access by read/write
+	 * and create symlink/remove symlink.
+	 */
+	struct mutex			lock;
+	int				refcnt;
 };
 
 #endif /* U_GETHER_H */