usb: gadget: configfs: allow setting function instance's name

USB function's configfs config group is created in a generic way in
usb/gadget/configfs.c:function_make(), which in turn delegates actual
allocation and setup of the USB function instance to a particular
implementation, e.g. in f_acm.c. The said implementation does its job
in a parameter-less function e.g. acm_alloc_instance(), which results
in creating an unnamed config group, whose name is set later in
function_make(). function_make() creates the name by parsing a string
of the form:

<function name>.<instance name>

which comes from userspace as a parameter to mkdir invocation.

Up to now only <function name> has been used, while <instance name>
has been ignored. This patch adds a set_inst_name() operation to
struct usb_function_instance which allows passing the <instance name>
from function_make() so that it is not ignored. It is entirely up to the
implementor of set_inst_name() what to do with the <instance name>.

In a typical case, the struct usb_function_instance is embedded in a
larger struct which is retrieved in set_inst_name() with container_of(),
and the larger struct contains a field to store the <instance name>.

Signed-off-by: Andrzej Pietrasiewicz <andrzej.p@samsung.com>
Signed-off-by: Kyungmin Park <kyungmin.park@samsung.com>
Acked-by: Michal Nazarewicz <mina86@mina86.com>
Signed-off-by: Felipe Balbi <balbi@ti.com>

1 files changed, 2 insertions, 0 deletions

diff --git a/include/linux/usb/composite.h b/include/linux/usb/composite.h
index 5e61589fc166..dba63f53906c 100644
--- a/include/linux/usb/composite.h
+++ b/include/linux/usb/composite.h
@@ -468,6 +468,8 @@ struct usb_function_instance {
 	struct config_group group;
 	struct list_head cfs_list;
 	struct usb_function_driver *fd;
+	int (*set_inst_name)(struct usb_function_instance *inst,
+			      const char *name);
 	void (*free_func_inst)(struct usb_function_instance *inst);
 };