usb: gadget: configfs: OS Extended Compatibility descriptors support

Add handling of OS Extended Compatibility descriptors from configfs interface.
Hosts which expect the "OS Descriptors" ask only for configurations @ index 0,
but linux-based USB devices can provide more than one configuration.
This patch adds marking one of gadget's configurations the configuration
to be reported at index 0, regardless of the actual sequence of usb_add_config
invocations used for adding the configurations. The configuration is selected
by creating a symbolic link pointing to it from the "os_desc" directory
located at the top of a gadget's directory hierarchy.

One kind of "OS Descriptors" are "Extended Compatibility Descriptors",
which need to be specified per interface. This patch adds interface.<n>
directory in function's configfs directory to represent each interface
defined by the function. Each interface's directory contains two attributes:
"compatible_id" and "sub_compatible_id", which represent 8-byte
strings to be reported to the host as the "Compatible ID" and "Sub Compatible
ID".

Signed-off-by: Andrzej Pietrasiewicz <andrzej.p@samsung.com>
Signed-off-by: Felipe Balbi <balbi@ti.com>

1 files changed, 6 insertions, 0 deletions

diff --git a/include/linux/usb/composite.h b/include/linux/usb/composite.h
index 549f5382b01a..9c3903d76781 100644
--- a/include/linux/usb/composite.h
+++ b/include/linux/usb/composite.h
@@ -80,12 +80,16 @@ struct usb_os_desc_ext_prop {
  * @ext_prop: Extended Properties list
  * @ext_prop_len: Total length of Extended Properties blobs
  * @ext_prop_count: Number of Extended Properties
+ * @opts_mutex: Optional mutex protecting config data of a usb_function_instance
+ * @group: Represents OS descriptors associated with an interface in configfs
  */
 struct usb_os_desc {
         char                    *ext_compat_id;
         struct list_head        ext_prop;
         int                     ext_prop_len;
         int                     ext_prop_count;
+        struct mutex            *opts_mutex;
+        struct config_group     group;
 };
 
 /**
@@ -381,6 +385,8 @@ extern void usb_composite_unregister(struct usb_composite_driver *driver);
 extern void usb_composite_setup_continue(struct usb_composite_dev *cdev);
 extern int composite_dev_prepare(struct usb_composite_driver *composite,
                 struct usb_composite_dev *cdev);
+extern int composite_os_desc_req_prepare(struct usb_composite_dev *cdev,
+                                         struct usb_ep *ep0);
 void composite_dev_cleanup(struct usb_composite_dev *cdev);
 
 static inline struct usb_composite_driver *to_cdriver(