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>

4 files changed, 78 insertions, 1 deletions

diff --git a/Documentation/ABI/testing/configfs-usb-gadget-subset b/Documentation/ABI/testing/configfs-usb-gadget-subset
new file mode 100644
index 000000000000..f47170a2f7dc
--- /dev/null
+++ b/Documentation/ABI/testing/configfs-usb-gadget-subset
@@ -0,0 +1,14 @@
+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
diff --git a/drivers/usb/gadget/Kconfig b/drivers/usb/gadget/Kconfig
index 0a444f39109f..3a72b9dbf7f0 100644
--- a/drivers/usb/gadget/Kconfig
+++ b/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
diff --git a/drivers/usb/gadget/f_subset.c b/drivers/usb/gadget/f_subset.c
index 089881a530d5..fbc7a24942e4 100644
--- a/drivers/usb/gadget/f_subset.c
+++ b/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";
diff --git a/drivers/usb/gadget/u_gether.h b/drivers/usb/gadget/u_gether.h
index 3a4a2bf61cdc..d4078426ba5d 100644
--- a/drivers/usb/gadget/u_gether.h
+++ b/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 */